38 Examples of Zoonotic Diseases

Zoonotic diseases are infections transmitted from animals to humans. These diseases, caused by bacteria, viruses, parasites, or fungi, underscore the intricate interplay between human, animal, and environmental health. Examples include rabies, transmitted via bites from infected animals; Lyme disease, spread by ticks; and avian influenza, which originates in birds. The Ebola virus is transmitted to humans through contact with infected animal’s bodily fluids, while the SARS-CoV-2 virus, responsible for COVID-19, is believed to have zoonotic origins, possibly linked to bats. Effective management of zoonotic diseases necessitates a holistic “One Health” approach, addressing all interconnected areas of potential outbreak.

Zoonotic Diseases

Zoonotic diseases, or zoonoses, are infections transmitted between animals and humans. They can be caused by bacteria, viruses, parasites, and fungi. These diseases can spread through direct contact with animals, consumption of contaminated food or water, vectors like ticks or mosquitoes, or even through the air. Examples include rabies from bites, Lyme disease from ticks, and the recent COVID-19 caused by the SARS-CoV-2 virus. Understanding zoonoses is vital because a significant proportion of new or emerging infectious diseases in humans originate from animal hosts. Proper measures in animal and environmental health can prevent many zoonotic infections.

Transmission of Zoonotic Diseases

Zoonotic diseases can be transmitted from animals to humans in various ways. The main modes of transmission include:

1. Direct Contact

• Involves physical contact with the infected animals.

• Handling animals or animal products.

• Touching feces, urine, blood, or bodily fluids.

• Bites or scratches (e.g., rabies from dogs or bats).

2. Indirect Contact

• Without direct physical contact with the infected animals.

• Contact with areas where animals live and roam (e.g., barns, petting zoos, or caves).

• Touching objects or surfaces contaminated with germs from animals (e.g., aquarium tank water, pet food, pet dishes).

3. Vector-borne

• Through insects that carry pathogens from animals to humans.

• Mosquitoes (e.g., West Nile virus, Zika).

• Ticks (e.g., Lyme disease).

• Fleas (e.g., plague from rodents).

4. Foodborne

• Consuming contaminated food or water.

• Eating undercooked meat, eggs, or dairy products.

• Drinking raw milk or contaminated water (e.g., certain E. coli infections from cattle).

5. Airborne

• Inhalation of pathogens.

• Respiratory droplets from infected animals (less common).

• Inhalation of dust from areas populated by certain animals (e.g., hantavirus from rodent excreta).

6. Oral Transmission

• Through consumption or licking.

• Occurs when an individual consumes or licks the pathogen, often from their hands after handling an animal or its environment.

The risk of acquiring a zoonotic disease can be reduced with preventive measures, such as regular hand washing, safe food practices, avoiding contact with sick animals, and using insect repellent. Given the significant public health implications of zoonotic diseases, understanding their transmission routes is essential for prevention and control strategies.

Classification of Zoonotic Diseases

Zoonotic diseases or zoonoses can be classified based on various factors such as the causative agent, the mode of transmission, or the reservoir host. Here’s a basic classification based on these criteria:

1. Based on Causative Agent

1. Viral Zoonoses

• Rabies

• Ebola

• Zika Virus

• SARS-CoV-2 (COVID-19)

2. Bacterial Zoonoses

• Lyme disease (Borrelia burgdorferi)

• Plague (Yersinia pestis)

• Brucellosis (Brucella spp.)

• Leptospirosis (Leptospira spp.)

3. Parasitic Zoonoses

• Toxoplasmosis (Toxoplasma gondii)

• Malaria (Plasmodium spp.)

• Leishmaniasis (Leishmania spp.)

• Trypanosomiasis (Trypanosoma spp.)

4. Fungal Zoonoses

• Ringworm (Dermatophytes)

• Sporotrichosis (Sporothrix schenckii)

5. Protozoal Zoonoses

• Giardiasis (Giardia lamblia)

• Cryptosporidiosis (Cryptosporidium spp.)

6. Prion Zoonoses

• Variant Creutzfeldt-Jakob Disease (vCJD)

2. Based on the Mode of Transmission

1. Direct Transmission

• Rabies (through bites or scratches from infected animals)

• Brucellosis (through contact with infected animal tissues or fluids)

2. Indirect Transmission

• Lyme disease (through ticks)

• Malaria (through mosquitoes)

3. Foodborne and Waterborne

• Salmonellosis (consumption of contaminated food or water)

• Trichinosis (consumption of undercooked contaminated meat)

4. Airborne

• Influenza (through respiratory droplets)

• Hantavirus Pulmonary Syndrome (inhalation of aerosolized rodent excreta)

5. Vector-Borne

• West Nile Virus (through mosquito bites)

• Leishmaniasis (through sandfly bites)

3. Based on the Reservoir Host

1. Domestic Animal Reservoir

• Brucellosis

• Leptospirosis

2. Wild Animal Reservoir

• Ebola Virus Disease (fruit bats are believed to be the natural host)

• Lyme disease (rodents are primary reservoirs)

3. Human Reservoir

• HIV/AIDS

• Tuberculosis (Mycobacterium tuberculosis)

4. Based on Impact or Occurrence

1. Endemic Zoonoses

• These are constantly present in a specific geographical area, e.g., Lyme disease in some regions.

2. Epidemic/Pandemic Zoonoses

• These occur in widespread outbreaks, often crossing international borders, e.g., COVID-19.

3. Emerging Zoonoses

• These are newly recognized or evolved strains, or those that have changed their host range or geographical distribution, e.g., Avian Influenza.

4. Neglected Zoonoses

• These are zoonoses that are overlooked in public health agendas despite causing significant morbidity and mortality, particularly in low and middle-income countries, e.g., bovine tuberculosis.

This classification is not exhaustive or mutually exclusive, as many zoonoses may fit into multiple categories depending on different criteria or perspectives. Nonetheless, this classification provides a foundational understanding of zoonotic diseases.

Zoonotic Diseases of Domestic Animals

Domestic animals, including pets and livestock, play a crucial role in the transmission of several zoonotic diseases to humans. These infections can pass between animals and humans through various means, including direct contact, ingestion of contaminated food or water, or via vectors like ticks and mosquitoes.

Zoonotic Diseases of Pets, Companion Animals, and Birds

Pets and companion animals, including birds, can transmit several zoonotic diseases to humans. Rabies, primarily from dog and cat bites, is a fatal viral infection impacting the nervous system. Toxoplasmosis, caused by a protozoan parasite, often originates from cat feces. Reptile-associated salmonellosis can arise from handling reptiles like turtles or terrariums. Birds can transmit psittacosis (parrot fever) caused by the bacterium Chlamydia psittaci. Additionally, pet rodents can be reservoirs for diseases like hantavirus. Safe handling, hygiene practices, and regular veterinary checks can help mitigate the risks associated with these zoonotic diseases.

Zoonotic Diseases of Fish and Aquatic Environments

Fish and aquatic environments are sources of several zoonotic diseases. Mycobacteriosis (fish tank granuloma) can be contracted from handling infected fish or contaminated water, caused by bacteria like Mycobacterium marinum. Vibrio infections, especially Vibrio vulnificus, can arise from consuming raw seafood or exposing wounds to brackish water. Ciguatera fish poisoning results from eating fish that consume ciguatoxin-containing microalgae. Anisakiasis is caused by ingesting larvae present in raw or undercooked seafood. Ensuring proper food preparation, maintaining aquarium hygiene, and avoiding raw fish consumption in endemic areas can help prevent these zoonotic diseases.

Zoonotic Diseases Associated with Food-Borne Pathogens

Food-borne zoonoses are diseases transmitted to humans through the consumption of contaminated food products. Salmonellosis and Campylobacteriosis arise from ingesting undercooked poultry or meat. Listeriosis, caused by Listeria monocytogenes, can be contracted from unpasteurized dairy or processed meats. E. coli O157:H7 infections result from eating contaminated beef or produce. Brucellosis is linked to unpasteurized milk or cheese. Trichinellosis stems from consuming undercooked pork infected with Trichinella larvae. Toxoplasmosis, though commonly associated with cat feces, can also be contracted from undercooked meat. Proper food handling, preparation, and storage reduce the risk of these zoonotic infections.

Impact of Zoonotic Diseases

Zoonoses have profound impacts on various facets of society, health, and the economy. Here’s an overview of their effects:

1. Human Health

1. Morbidity and Mortality

• Diseases like rabies, Ebola, and avian influenza can have high mortality rates.

2. Emerging Infectious Diseases

• Over 60% of emerging infectious diseases in humans are zoonotic in origin, including COVID-19, SARS, and MERS.

2. Economic

• Trade Restrictions

Outbreaks can lead to trade bans, affecting exports of animals and animal products.

• Livestock Losses

Diseases can decrease productivity or lead to mass culling.

• Healthcare Costs

Managing outbreaks and treating patients can strain healthcare budgets.

3. Socio-Cultural

• Cultural Practices

Traditional practices related to animal handling or consumption can increase zoonotic transmission risks.

• Livelihoods

Rural communities, particularly those depending on livestock, can be disproportionately affected.

4. Environmental

• Biodiversity Loss

Some zoonotic diseases, like the amphibian chytrid fungus, lead to significant declines in wildlife populations.

• Land Use Changes

Deforestation and urbanization can alter wildlife habitats, leading to increased human-animal interactions and potential disease spillover.

5. Security

• National Security

Severe outbreaks can destabilize governments and economies posing threats to national security.

• Biological Warfare Concerns

Some zoonotic agents, such as anthrax, have potential use as bioweapons.

6. Globalization and Urbanization

• Rapid Spread

Increased global travel and trade can facilitate the swift international spread of zoonoses.

• Urban Transmission

High-density populations can amplify transmission as seen in some COVID-19 hotspots.

7. Research and Innovation

• Vaccine and Drug Development

Zoonotic outbreaks often stimulate research into new vaccines and treatments.

• Surveillance Systems

The need to detect and respond to outbreaks has led to innovations in disease surveillance.

Given their wide-ranging impacts, controlling and preventing zoonoses is crucial. The “One Health” approach, which integrates human, animal, and environmental health, is recognized as a comprehensive strategy to tackle these diseases.

Control of Zoonotic Diseases

Controlling zoonoses is paramount for public health, agricultural sustainability, and economic stability. An integrated approach, often referred to as the “One Health” model, which encompasses human, animal, and environmental health, is essential. Here are some measures and strategies to control zoonoses:

1. Surveillance and Monitoring

• Detect outbreaks early through regular disease surveillance in both human and animal populations.

• Implement sentinel surveillance in hotspot regions.

2. Vaccination

• Vaccinate susceptible animal populations (e.g., rabies vaccination for dogs).

• Develop and distribute human vaccines for high-risk diseases.

3. Public Health Education

• Educate communities about zoonotic risks and preventive measures.

• Promote proper food handling, cooking, and storage practices.

4. Regulation and Legislation

• Enforce animal movement controls to prevent the spread of diseases.

• Regulate food production and processing facilities for hygiene and safety.

5. Vector Control

• Implement measures to reduce populations of disease vectors such as mosquitoes or ticks.

• Promote the use of personal protective measures like bed nets and repellents.

6. Animal Health

• Regular health checks and treatment for livestock and pets.

• Implement biosecurity measures on farms to prevent the introduction or spread of pathogens.

7. Environmental Management

• Address deforestation, urbanization, and land-use changes that increase human-wildlife interactions.

• Manage wildlife habitats to reduce contact with humans and domestic animals.

8. Quarantine and Isolation

• Isolate infected animals or humans to prevent disease spread.

• Implement quarantine measures for imported animals.

9. Research and Collaboration

• Foster interdisciplinary collaboration between veterinarians, doctors, ecologists, and other professionals.

• Fund research on disease ecology, diagnostics, treatments, and prevention.

10. Community Engagement

• Engage local communities in surveillance, reporting, and control activities.

• Understand and respect local customs and traditions while promoting behavior change.

11. Rapid Response Teams

• Establish and train rapid response teams to handle outbreaks.

• Develop contingency plans for potential zoonotic outbreaks.

Effective control of zoonoses requires a coordinated, multi-sectoral effort at local, national, and global levels. With globalization and increasing human-animal interactions, proactive strategies are more crucial than ever.

Examples of Zoonotic Diseases 

1. Rabies

1. Cause

• Rabies is caused by the rabies virus, which belongs to the Lyssavirus genus.

2. Symptoms

The disease manifests in two main forms: furious and paralytic.

• Furious rabies

Hyperactivity, aggressive behavior, hydrophobia (fear of water), and aerophobia (fear of fresh air). These symptoms progress to delirium, hallucinations, and insomnia.

• Paralytic rabies

This form is less common and is characterized by muscle weakness, followed by paralysis. It progresses more slowly than furious rabies.

Both forms ultimately lead to coma and death.

3. Transmission

• Rabies is primarily transmitted through the bite or scratch of an infected animal, often a dog. The virus is present in the saliva of rabid animals. Other less common routes of transmission include exposure to the virus through mucous membranes or an open wound, or via organ transplantation from an infected donor.

4. Treatment

• Once clinical signs of rabies appear, the disease is almost always fatal. Treatment at this stage is typically supportive. However, rabies is preventable if appropriate post-exposure prophylaxis (PEP) is provided promptly after exposure. PEP involves a series of rabies vaccines and, in certain cases, rabies immune globulin.

5. Prevention

• Vaccination of domestic animals

Dogs, in particular, should be vaccinated against rabies, as they are the most common source of human infections worldwide.

• Avoid contact with wild animals

Avoid contact with wild animals, especially those behaving oddly or appearing ill.

• Secure your living areas

Close windows and doors in the evening to keep bats out.

• Educate and raise awareness

Educate communities, especially children, about the risks of rabies and how to avoid animal bites.

• If bitten

If bitten, use soap and water for at least 15 minutes and seek medical attention immediately, even if the animal seems healthy.

• Post-exposure prophylaxis (PEP)

If exposed or bitten, it’s essential to receive rabies vaccination promptly.

Controlling rabies in animal populations, combined with timely post-exposure treatments, can effectively prevent human rabies cases.

2. Lyme Disease

1. Cause

• Lyme disease is caused by the spirochete bacterium, Borrelia burgdorferi. In Europe and Asia, Borrelia afzelii and Borrelia garinii also cause Lyme disease.

2. Symptoms

The symptoms of Lyme disease can present in multiple stages:

• Early localized stage

Flu-like symptoms such as fever, chills, fatigue, body aches, headache, neck stiffness, and swollen lymph nodes. One of the hallmark signs is a circular, red rash with a central clearing that looks like a “bull’s-eye,” but not everyone with Lyme disease gets this rash.

• Early disseminated stage

Multiple rashes, facial palsy, arthritis with severe joint pain and swelling, heart palpitations, dizziness, nerve pain, and meningitis symptoms.

• Late disseminated stage

Arthritis, neurological problems (like meningitis, encephalopathy, and peripheral neuropathy), and cardiac involvement.

3. Transmission

• Lyme disease is primarily transmitted to humans through the bite of infected black-legged ticks (commonly known as deer ticks). Young nymph ticks are typically the size of a poppy seed whereas adult ticks are slightly larger.

4. Treatment

• Lyme disease is treated with antibiotics. Early-stage Lyme disease can be treated with oral antibiotics like doxycycline or amoxicillin. More severe cases might require intravenous antibiotics.

5. Prevention

• Avoid tick habitats

Especially wooded, brushy, and grassy areas.

• Use repellents

Apply repellents containing DEET on skin and clothing.

• Wear protective clothing

Wear long pants and long-sleeved shirts. Tuck pants into socks to prevent ticks from getting under clothing.

• Check for ticks daily

Examine all parts of the body carefully and remove ticks immediately.

• Shower soon after being outdoors

Showering within two hours of coming indoors can reduce the risk of Lyme disease by washing off unattached ticks.

• 0.5% permethrin

Treat clothing and gear with products containing 0.5% permethrin

• Check pets

Pets can carry ticks into the home; so, they should be checked and protected with tick-prevention products.

• Maintain your yard

Clear tall grasses and brush, and keep the lawn short to reduce tick habitats.

Prompt removal of ticks is crucial. If a tick is removed within 24 hours, the chances of it transmitting Lyme disease or other pathogens are lessened.

3. Avian Influenza (Bird Flu)

1. Cause

• Avian influenza is caused by influenza A viruses, which are classified into subtypes based on two surface proteins: hemagglutinin (H) and neuraminidase (N). Highly pathogenic variants, like H5N1 and H7N9, have caused serious concerns due to their potential to cause severe disease in humans.

2. Symptoms

Symptoms in humans can range from typical flu-like symptoms to severe respiratory illness and complications:

• Fever

• Cough

• Sore throat

• Muscle aches

• Eye infections (conjunctivitis)

• Severe respiratory distress

• Pneumonia

• Organ failure

• Death in severe cases

3. Transmission

Bird flu primarily affects birds, but it can sometimes jump to humans. Modes of transmission include:

• Direct contact with infected birds or their secretions/excretions.

• Handling or preparing infected poultry for cooking.

• Visiting live bird markets.

• Inhalation of airborne virus particles in places with infected birds.

• Rare human-to-human transmission has been reported but is not common.

4. Treatment

• The main treatment for human cases of avian influenza is antiviral medication, particularly oseltamivir (Tamiflu) or zanamivir (Relenza). These are most effective when administered early after symptom onset. Supportive care is often necessary for severe cases.

5. Prevention

• Poultry culling

Infected or potentially infected birds should be safely culled to prevent the spread.

• Biosecurity measures

Farms should have strict measures to prevent the introduction of the virus such as protective clothing for workers and disinfection protocols.

• Avoid direct contact

Avoid direct contact with live birds, especially in countries with known outbreaks.

• Avoid consumption of raw or undercooked poultry

Avoid consumption of raw or undercooked poultry or poultry products.

• Regular handwashing

Regular handwashing with soap and water especially after contact with birds or their environments.

• Vaccination

While there’s no specific vaccine for humans against most strains of avian influenza, vaccines for poultry are sometimes used in endemic areas.

• Avoidance of live bird markets

Avoid live bird markets and areas where avian influenza is endemic.

• Awareness and monitoring

Constant surveillance and rapid reporting of outbreaks help in early detection and management.

The risk of avian influenza can be minimized with the right precautions, especially in areas where outbreaks in birds have been reported. The disease remains a concern due to its potential to mutate and cause wider human outbreaks.

4. Ebola Virus Disease

1. Cause

• EVD is caused by the Ebola virus which belongs to the Filoviridae family. There are five known species of the Ebola virus, with the Zaire ebolavirus being the most virulent and responsible for the majority of human cases.

2. Symptoms

Symptoms typically appear 2 to 21 days after exposure. Early symptoms resemble other tropical diseases, but they can progress to more severe forms quickly:

• Fever

• Severe headache

• Muscle pain

• Weakness

• Fatigue

• Diarrhea

• Vomiting

• Abdominal pain

• Unexplained hemorrhaging (bleeding or bruising)

3. Transmission

The virus is introduced into the human population through close contact with the blood, organs, or bodily fluids of infected animals, such as fruit bats, chimpanzees, and gorillas. Human-to-human transmission can occur via direct contact with:

• Blood or body fluids of a person who is sick or has died from EVD.

• Objects contaminated with the virus (e.g., needles).

• Semen from men who have recovered from EVD (the virus can persist for some time).

• Direct contact with the body of a deceased EVD patient.

4. Treatment

There’s no approved drug specifically for EVD. Treatment remains primarily supportive and includes:

• Rehydration (oral or intravenous)

• Treatment of specific symptoms

• Maintaining oxygen status and blood pressure

• Treating concurrent infections

However, some experimental treatments have shown promise, and in 2020, the U.S. FDA approved the first drug, Inmazeb (a mixture of three monoclonal antibodies), for the treatment of EVD.

5. Prevention

• Rapid detection and isolation

Quick identification and isolation of EVD patients play a crucial role in outbreak control.

• Protective measures for healthcare workers

This includes wearing protective clothing and following strict infection control measures.

• Safe burial practices

Traditional burial rituals can contribute to the spread. Safe practices are essential.

• Avoid consumption of bushmeat

Particularly in regions where the virus might circulate.

• Awareness campaigns

Informing the public about the disease and how it spreads.

• Regular handwashing

An essential practice to avoid many diseases, including EVD.

• Vaccination

An experimental vaccine named rVSV-ZEBOV has shown high efficacy in clinical trials and has been used in outbreak responses.

Controlling EVD outbreaks requires a combination of community engagement, good public health practices, and the integration of medical and scientific interventions, including vaccination.

5. Middle East Respiratory Syndrome (MERS)

1. Cause

• MERS is caused by the Middle East respiratory syndrome coronavirus (MERS-CoV).

2. Symptoms

Symptoms can range from mild to severe, and some individuals can remain asymptomatic:

• Fever

• Cough

• Shortness of breath

• Pneumonia (often seen on chest X-rays)

• Gastrointestinal symptoms (diarrhea, nausea, vomiting)

• Kidney failure in severe cases

3. Transmission

MERS-CoV is believed to be a zoonotic virus, with camels being a major reservoir. Modes of transmission include:

• Direct or indirect contact with infected camels.

• Human-to-human transmission, especially in healthcare settings where appropriate preventive measures are not followed. Close contact with a MERS patient can lead to transmission.

• Consuming camel products, like raw milk or undercooked meat, might pose risks, but the exact role of these products in transmission is not fully understood.

4. Treatment

There’s no specific antiviral treatment for MERS. Treatment remains supportive and includes:

• Rehydration

• Oxygen therapy (for patients with respiratory symptoms)

• Mechanical ventilation in severe cases

• Support for affected vital organs

5. Prevention

• Hygienic practices

Regular handwashing with soap and water.

• Avoid close contact with camels

Avoid close contact with camels, especially sick camels. Avoid touching their eyes, nose, or mouth.

• Avoid consuming raw camel products

Ensure camel milk is boiled and meat is cooked thoroughly.

• Protective measures for healthcare workers

Strict adherence to infection prevention and control measures.

• Isolation of patients

Patients suspected or confirmed to have MERS should be isolated and provided care with necessary precautions.

• Travel Advisories

During outbreaks, potential travelers should be aware of the situation and take necessary precautions.

• Public awareness

Educate the public about the risks and preventive measures.

Prompt identification, isolation, and management of MERS patients, combined with the right preventive measures, especially in healthcare settings, can help control potential outbreaks.

6. Severe Acute Respiratory Syndrome (SARS)

1. Cause

• SARS is caused by the SARS coronavirus, known as SARS-CoV. It’s worth noting that the virus responsible for COVID-19 is a related virus named SARS-CoV-2 but the two diseases are distinct.

2. Symptoms

Symptoms of SARS typically appear after a 2-7 day incubation period:

• High fever

• Chills and rigors

• Headache

• Muscle aches

• Dry cough

• Fatigue or malaise

• Difficulty in breathing

• Pneumonia, often confirmed by a chest X-ray

• Diarrhea in some cases

3. Transmission

SARS-CoV primarily spreads through respiratory droplets when an infected person coughs or sneezes.

• Close person-to-person contact, especially if someone comes into contact with infectious droplets.

• Touching surfaces contaminated with the virus, then touching the mouth, nose, or eyes.

• Rarely, the virus can spread through fecal contamination.

4. Treatment

No specific antiviral treatment was proven to be effective against SARS. Treatment was largely supportive:

• Antipyretics for fever.

• Oxygen therapy for respiratory symptoms.

• Mechanical ventilation for severe respiratory distress.

• Antibiotics to treat bacterial co-infections, though they do not work against the SARS virus itself.

• Some patients were treated with antiviral medications and steroids, but their effectiveness remains uncertain.

5. Prevention

• Isolation of patients

Suspected or confirmed SARS patients were isolated to prevent the spread.

• Quarantine of close contacts

To monitor for symptoms and reduce the potential for spread.

• Infection control in healthcare settings

Including the use of protective gear like masks, gloves, and gowns.

• Travel advisories and screening

During the SARS outbreak, affected areas saw travel restrictions, advisories, and airport screenings.

• Public awareness

Providing information on symptoms, transmission, and preventive measures.

• Regular hand hygiene

Washing hands with soap and water or using an alcohol-based hand sanitizer.

• Avoid touching the face

Especially the eyes, nose, and mouth with unwashed hands.

• Wearing a mask

Particularly in areas with known cases.

The global SARS outbreak of 2002-2003 was eventually contained, and no cases related to the original outbreak have been reported since 2004. The rapid international response, combined with effective public health measures, played a crucial role in controlling the disease.

7. COVID-19

1. Cause

• COVID-19 is caused by the novel coronavirus, SARS-CoV-2.

2. Symptoms

Symptoms can vary widely, from being asymptomatic (showing no symptoms) to severe respiratory distress. Typical symptoms include:

• Fever or chills

• Cough

• Shortness of breath or difficulty breathing

• Fatigue

• Muscle or body aches

• Headache

• Loss of taste or smell

• Sore throat

• Congestion or runny nose

• Nausea or vomiting

• Diarrhea

Severe symptoms that require immediate medical attention include difficulty breathing, persistent chest pain, confusion, inability to stay awake, and bluish lips or face.

3. Transmission

SARS-CoV-2 primarily spreads through respiratory droplets:

• Between people in close contact (within about 6 feet).

• By inhaling droplets produced when an infected person coughs, sneezes, talks, or breathes.

• By touching a surface or object with the virus on it and then touching the mouth, nose, or eyes, though this is not the primary way the virus spreads.

4. Treatment

• There are antiviral treatments approved under Emergency Use Authorizations (EUAs), including Remdesivir and oral antiviral medications.

• Dexamethasone, a corticosteroid, has been used for patients requiring supplemental oxygen.

• Monoclonal antibodies have been authorized for certain patients.

• Hospitalized patients might receive supportive care such as supplemental oxygen or mechanical ventilation in severe cases.

• Ongoing research continues into other potential treatments.

5. Prevention

• Vaccination

Multiple COVID-19 vaccines have been developed and authorized around the world. Vaccination significantly reduces the risk of severe disease, hospitalization, and death.

• Wear masks

Especially in areas with high transmission rates or in crowded settings.

• Physical distancing

Stay at least 6 feet away from individuals not from your household.

• Hand hygiene

Regularly wash hands with soap and water for at least 20 seconds or use hand sanitizers with at least 60% alcohol.

• Avoid crowded and poorly ventilated areas

Improve ventilation in indoor settings when possible.

• Follow local health guidelines

As recommendations can vary based on local transmission rates and healthcare capacities.

• Stay home if feeling unwell

Stay home if feeling unwell to prevent the potential spread.

• Regular testing

Especially if exposed or showing symptoms, to detect and isolate cases.

The response to COVID-19 is dynamic, with guidelines and recommendations evolving as more is understood about the virus and its effects. It’s crucial to refer to current sources like the World Health Organization (WHO) or the Centers for Disease Control and Prevention (CDC) for up-to-date information.

8. Zika Virus

1. Cause

• The Zika virus is caused by the Zika virus, a member of the Flavivirus family, which also includes the dengue, yellow fever, and West Nile viruses.

2. Symptoms

Many people infected with the Zika virus won’t have symptoms or will have only mild symptoms. Those exhibit symptoms might experience:

• Fever

• Rash

• Headache

• Joint pain

• Conjunctivitis (red eyes)

• Muscle pain

Symptoms can last for several days to a week. Severe disease requiring hospitalization is uncommon, and death is rare.

3. Transmission

The primary transmission route for the Zika virus is through the bite of an infected Aedes mosquito, especially Aedes aegypti. Other modes of transmission include:

• From mother to fetus during pregnancy, leading to congenital Zika syndrome in some cases.

• Through sexual contact.

• Through blood transfusion (though very rare).

• Possibly through organ transplantation.

4. Treatment

There’s no specific antiviral treatment for the Zika virus. Treatment focuses on relieving symptoms:

• Rest.

• Rehydration.

• Analgesics and antipyretics like acetaminophen to reduce fever and pain.

• Avoiding aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) until dengue can be ruled out to reduce bleeding risk.

5. Prevention

• Avoid mosquito bites

This is the primary method of prevention. Use insect repellents, wear long-sleeved shirts and pants, use air conditioning or window/door screens, and sleep under mosquito nets in high-risk areas.

• Control mosquito populations

This involves draining standing water, where mosquitos breed, and using larvicides and insecticides.

• Safe sexual practices

Using condoms or abstaining from sex can prevent sexual transmission of the Zika virus.

• Pregnancy precautions

Women who are pregnant or planning to become pregnant and their partners should take precautions if they live in or are traveling to areas with Zika virus transmission. This might include delaying travel or taking steps to avoid mosquito bites and practicing safe sex.

• Blood screening

In areas with active Zika virus transmission, screening the blood supply for the virus can help prevent transmission via blood transfusion.

As of January 2022, ongoing research aims to develop a vaccine against the Zika virus, but none has been approved for general use yet.

9. Salmonellosis

1. Cause

• Salmonellosis is caused by bacteria belonging to the genus Salmonella. Two species, Salmonella bongori and Salmonella enterica, are known, with the latter being responsible for most human infections.

2. Symptoms

Symptoms typically appear 6 hours to 6 days after infection and can last 4-7 days:

• Diarrhea

• Fever

• Abdominal cramps

• Vomiting

• Nausea

• Headache

In some cases, the infection can spread from the intestines to the bloodstream and then to other body sites, leading to more severe conditions that may require hospitalization.

3. Transmission

Salmonellosis is primarily transmitted through the fecal-oral route:

• Consuming contaminated food or water. Common sources include raw or undercooked eggs, poultry, meat, unpasteurized milk, and other dairy products.

• Direct contact with infected animals or their environment. This includes pets like turtles, birds, and rodents.

• Person-to-person transmission via the fecal-oral route, especially in settings with poor hygiene.

4. Treatment

Most cases of salmonellosis are mild and resolve without specific treatment. Supportive care includes:

• Rehydration with oral rehydration salts or intravenous fluids for severe cases.

• Antidiarrheal medication might be given in certain cases.

• Antibiotics are typically reserved for severe cases, those at high risk for complications (like infants, elderly individuals, and immunocompromised patients), and when the infection spreads beyond the intestines.

5. Prevention

• Safe food handling and preparation

Cook poultry, ground beef, and eggs thoroughly. Avoid consuming raw or undercooked eggs and unpasteurized milk.

• Proper hand hygiene

Wash hands with soap and water before handling food, after using the bathroom, changing diapers, or handling animals.

• Safe water

Drink and use safe water. When in doubt, boil or treat water before consumption.

• Avoid raw or undercooked seafood

Especially from polluted waters.

• Proper storage of food

Refrigerate foods promptly; don’t leave perishables out for extended periods.

• Avoid direct contact with reptiles

Turtles, iguanas, and other reptiles are known carriers. If contact occurs, wash hands immediately.

• Safe handling of pet food

Including dry pet foods and treats, as they can sometimes be contaminated.

Public health interventions, proper food safety regulations, and community education play crucial roles in the prevention of salmonellosis outbreaks.

10. West Nile Virus

1. Cause

• West Nile Virus is caused by the West Nile virus, a member of the Flavivirus genus, which also includes Zika, dengue, and yellow fever viruses.

2. Symptoms

The majority of people (about 80%) infected with WNV do not develop any symptoms. For those who do:

• Mild symptoms (West Nile fever)

Fever, headache, body aches, joint pains, vomiting, diarrhea, or rash. Fatigue and weakness can last for weeks or months.

• Severe symptoms

About 1 in 150 infected people develop severe illness affecting the central nervous system such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membranes surrounding the brain and spinal cord). Symptoms may include high fever, headache, stiff neck, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis.

3. Transmission

• Primary mode

Bites from infected mosquitoes, especially Culex species.

• Other modes

Other modes, though rarer, include transfusions of infected blood, organ transplantation, and from mother to baby during pregnancy, delivery, or breastfeeding.

4. Treatment

There’s no specific antiviral treatment for WNV. Treatment is supportive:

• Over-the-counter pain relievers can be used to reduce fever and relieve some symptoms.

• In severe cases, patients often need to be hospitalized to receive support like intravenous fluids, pain medication, and nursing care.

• Severe cases involving encephalitis or meningitis may require hospitalization, supportive therapy, and monitoring.

5. Prevention

• Mosquito control

This includes draining standing water and the use of larvicides and insecticides.

• Avoid mosquito bites

Use insect repellent, wear long sleeves and pants during peak mosquito hours (dawn and dusk), use air conditioning or window/door screens, and sleep under mosquito nets in high-risk areas.

• Maintain screens

Ensure that doors and windows have tight-fitting screens without holes.

• Blood screening

In areas with outbreaks, blood banks might screen for WNV to ensure the virus isn’t passed on in blood transfusions.

Vaccine development for WNV has been a focus of research, but as of January 2022, no vaccine for humans was available. However, there are vaccines available for horses, a species also susceptible to the virus.

11. Brucellosis

1. Cause

• Brucellosis, also known as “Malta fever” or “Mediterranean fever”, is caused by bacteria of the genus Brucella. Several species can cause human disease, including B. melitensis, B. abortus, B. suis, and B. canis.

2. Symptoms

Symptoms can appear anywhere from a few days to a few months after exposure and can range from mild to severe:

• Fever

• Sweats (often described as drenching night sweats)

• Fatigue

• Weakness

• Muscle and joint pain

• Weight loss

• Headache

• Pain in the liver area

More severe complications can include endocarditis, arthritis, or involvement of the central nervous system.

3. Transmission

• Consuming contaminated food

Especially unpasteurized milk, cheese, and other dairy products.

• Direct contact

With fluids or tissues from infected animals, which poses a risk to farmers, veterinarians, and slaughterhouse workers.

• Inhalation

Breathing in the bacteria poses a risk in laboratory settings.

• Rare Transmission 

Through sexual contact or from mother to child during childbirth.

4. Treatment

Brucellosis can be difficult to treat and can become chronic if not treated early and adequately.

• Combination of antibiotics over several weeks is typically required. Doxycycline and rifampin are commonly used together for several weeks.

• Other antibiotic combinations may be used, depending on drug resistance patterns and patient specifics.

• Treatment can be prolonged, and relapses are possible.

5. Prevention

• Avoid unpasteurized dairy

Especially when traveling in regions where brucellosis is common.

• Wear protective gear

Farmers, veterinarians, and slaughterhouse workers should use gloves and protective glasses when handling animals or animal tissues.

• Vaccinate livestock

While there is no vaccine for humans, vaccines for livestock have been developed and are used in many parts of the world.

• Cook meat thoroughly

While transmission from consuming undercooked meat is less common than from dairy, it’s still a potential risk.

• Laboratory precautions

Lab workers should use protective equipment and work under biosafety conditions to avoid accidental exposure.

Prompt diagnosis and treatment are essential to reduce the risk of complications from brucellosis. In regions where the disease is common, public health measures, including livestock vaccination and milk pasteurization, play a vital role in preventing human cases.

12. Anthrax

1. Cause

• Anthrax is caused by the bacterium Bacillus anthracis, a spore-forming bacterium. Depending on how the disease is contracted, anthrax can manifest in one of several forms: cutaneous, inhalation, gastrointestinal, or injection.

2. Symptoms

Symptoms vary based on the form of the disease:

1. Cutaneous Anthrax (most common)

• Bump resembling an insect bite that turns into a painless sore with a black center.

• Swelling can occur around the sore.

2. Inhalation Anthrax

• Early symptoms: fever, chills, shortness of breath, fatigue, cough, and mild chest pain.

• Later symptoms: severe respiratory distress, shock.

3. Gastrointestinal Anthrax

• Nausea, loss of appetite, vomiting, fever followed by abdominal pain, vomiting of blood, and severe diarrhea.

4. Injection Anthrax

• Fever and chills.

• Group of small blisters or bumps that may itch, appearing where the drug was injected.

• Swelling around the injection site.

3. Transmission

• Cutaneous

Through cuts or abrasions on the skin when handling contaminated animal products.

• Inhalation

Breathing in spores, e.g., from handling contaminated animal products or bioterrorism.

• Gastrointestinal

Eating undercooked meat from infected animals.

• Injection

Injecting illegal drugs contaminated with anthrax spores.

4. Treatment

Early detection and treatment are crucial for survival.

• Antibiotics

Such as ciprofloxacin, doxycycline, or penicillin are used to treat all forms of anthrax. The choice and duration of treatment depend on the form of anthrax and the circumstances of exposure.

• Supportive care

Especially for inhalation anthrax which can cause severe respiratory distress.

• Antitoxin

In certain cases, an antitoxin may be used in combination with antibiotics to neutralize the toxins produced by the bacteria.

5. Prevention

• Vaccination

A vaccine is available for certain groups of people at high risk, such as military personnel, some laboratory workers, and individuals handling potentially infected animals.

• Protective clothing

Wearing gloves and other protective gear when handling potentially contaminated animal products.

• Safe handling

Safely dispose of potentially contaminated animal products and ensure that imported animal products are from anthrax-free areas.

• Cooking meat

Ensure that meat is properly cooked before consumption.

• Post-exposure prophylaxis

Individuals who have been exposed to anthrax (e.g., in a bioterrorism event) might receive antibiotics to prevent the onset of the disease.

Preparedness and vigilance, especially regarding imported animal products and bioterrorism threats, are key to preventing outbreaks and individual cases of anthrax.

13. Q Fever

1. Cause

• Q Fever is caused by the bacterium Coxiella burnetii. The bacteria can survive in a spore-like state for extended periods in the environment.

2. Symptoms

Many people infected with C. burnetii do not show symptoms. For those who do, they might experience:

• Acute symptoms

High fever, severe headache, muscle pains, chills, fatigue, cough, nausea, vomiting, diarrhea, and sensitivity to light. Some might develop pneumonia or hepatitis.

• Chronic symptoms

Endocarditis (inflammation of the heart valves), fatigue, lingering weakness, night sweats, and shortness of breath.

3. Transmission

• Inhalation

Most common route, by inhaling dust that has been contaminated by infected animals’ birth products, urine, feces, or milk.

• Direct contact

With the aforementioned materials from an infected animal, typically through broken skin.

• Consumption

By ingesting raw milk or dairy products from infected animals.

• Ticks

Though not common, ticks can transmit the disease in some parts of the world.

4. Treatment

• Antibiotics

Doxycycline is the first-line treatment for acute Q fever. Chronic Q fever might require longer-term treatment and might include a combination of antibiotics.

• Monitoring and follow-up

Especially in chronic cases to ensure that the infection has been fully cleared.

5. Prevention

• Vaccination

A vaccine for Q fever is available in some countries, primarily for those at high risk.

• Protective clothing

Wearing gloves and protective clothing when working with potentially infected animals or animal products.

• Safe disposal

Proper disposal of birth products, especially placentas, when assisting with animal births.

• Pasteurization

Drinking pasteurized milk and consuming pasteurized dairy products can reduce the risk of getting Q fever from food.

• Airborne precautions

In laboratory environments, special airborne precautions can prevent inhalation of the bacteria.

• Regular animal screening

Regularly testing livestock for the presence of the bacteria and managing infected animals can help reduce the risk of transmission.

Q Fever is a concern mainly for people who work with livestock or in specific laboratory environments. Education and preventative measures are essential for these at-risk populations.

14. Hantavirus Pulmonary Syndrome (HPS)

1. Cause

• Hantavirus Pulmonary Syndrome (HPS) is caused by several strains of hantaviruses. In the Americas, a primary causative agent is the Sin Nombre virus.

2. Symptoms

The progression of HPS occurs in two phases:

1. Early symptoms

(1-5 weeks after exposure)

• Fatigue

• Fever and chills

• Muscle aches, especially in the thighs, hips, back, and sometimes shoulders.

• Headaches, dizziness, chills, and abdominal issues like nausea, vomiting, diarrhea, and abdominal pain.

2. Late symptoms

(4-10 days after the early symptoms)

• Coughing and shortness of breath as the lungs fill with fluid, leading to respiratory failure which can be severe.

3. Transmission

• Inhalation

The primary mode is through inhalation of airborne particles from rodent urine, droppings, or nesting materials, especially from deer mice in North America.

• Direct contact

By touching surfaces contaminated with rodent urine or droppings and then touching the face, though this is less common.

• Bites

Very rarely, through a bite from an infected rodent.

Hantaviruses are not known to be transmitted between humans.

4. Treatment

• No specific antiviral treatment

There’s no specific treatment or cure for HPS, but early diagnosis and medical treatment in an intensive care unit can significantly improve survival rates.

• Supportive care

Oxygen therapy to help with respiratory distress is the primary treatment. In severe cases, a patient might need a mechanical ventilator.

• Early intervention

Rapid progression to respiratory failure is common, so seeking medical attention immediately upon suspecting HPS is crucial.

5. Prevention

• Rodent control

This is the primary method of prevention. Seal up homes and buildings, trap rodents, and clean up potential nesting sites and food sources.

• Safe cleanup

Wet down areas of rodent infestation with a bleach solution before cleaning to reduce the risk of aerosolizing the virus.

• Avoidance

Avoid activities that might stir up dust in areas with signs of rodent activity, such as sweeping or vacuuming.

• Protective gear

Wear gloves and a well-fitting mask when cleaning up rodent-infested areas.

• Camping precautions

Avoid sleeping on bare ground; use a tent with a floor or a raised cot if possible.

Understanding the link between hantaviruses and rodent hosts is essential. Awareness and rodent control, especially in rural and semi-rural areas, can help reduce the risk of HPS.

15. Leptospirosis

1. Cause

• Leptospirosis is caused by bacteria of the genus Leptospira. There are many strains (serovars) of this bacterium that can cause disease in humans.

2. Symptoms

The symptoms of leptospirosis can range from mild to severe and can include:

• Sudden onset of fever, chills, and headache

• Muscle aches, especially in the calves and lower back

• Red and irritated eyes (conjunctival suffusion)

• Jaundice (yellowing of the skin and eyes)

• Abdominal pain, nausea, vomiting, and diarrhea

• Rash

In severe cases, the infection can lead to kidney or liver failure, meningitis (inflammation of the membrane around the brain and spinal cord), respiratory distress, or a rare severe form called Weil’s disease.

3. Transmission

• Contact with contaminated water or soil

The bacteria can enter the body through cuts or abrasions on the skin, or through the mucous membranes (like the eyes, nose, or mouth) after contact with contaminated water or soil.

• Direct contact

With the urine or tissues from infected animals.

• Consumption

Drinking contaminated water.

• Reservoirs

Common reservoirs include rodents, cattle, pigs, dogs, and wild animals.

4. Treatment

• Antibiotics

Doxycycline and penicillin are commonly used to treat leptospirosis. Early treatment is more effective and can prevent the disease from progressing to more severe stages.

• Supportive care

For dehydration, liver failure, or other complications.

• Hospitalization

Severe cases may require hospitalization for more intensive care and monitoring.

5. Prevention

• Avoid contaminated water

Do not swim or wade in water that might be contaminated with animal urine. If you must have contact with potentially contaminated water or soil, wear protective clothing like boots and gloves.

• Protective gear

For those who work with animals or in environments where the bacteria might be present.

• Rodent control

In urban settings, controlling rat populations can help reduce the risk of transmission.

• Vaccination

Some countries have vaccines for high-risk groups, like farmers or sewer workers. The protection provided by the vaccine may be short-lived and may not protect against all strains.

• Animal vaccination

Vaccinating livestock or pets in areas where leptospirosis is common.

• Clean environment

Ensure that the environment is clean and free from stagnant water, and avoid leaving food that can attract rodents.

Educating at-risk groups and ensuring good sanitation and regular rodent control measures can help prevent outbreaks of leptospirosis.

16. Nipah Virus Infection

1. Cause

• Nipah virus (NiV) is a member of the family Paramyxoviridae, genus Henipavirus. NiV was initially isolated and identified in 1999 during an outbreak of encephalitis and respiratory illness among pig farmers and people with close contact with pigs in Malaysia and Singapore.

2. Symptoms

The incubation period (interval from infection to the onset of symptoms) is believed to range between 4 and 14 days. Symptoms include:

• Fever and headache

• Dizziness and drowsiness

• Acute respiratory syndrome or atypical pneumonia

• Severe cases can progress to encephalitis (inflammation of the brain) with seizures and coma. This may lead to death or long-term neurological sequelae after recovery.

• Neck rigidity and muscle pain

3. Transmission

• Contact with infected animals

Especially fruit bats (flying foxes) which are natural hosts. Contact with pigs, which can be intermediate hosts, was implicated in early outbreaks.

• Consuming contaminated food

Such as raw date palm sap contaminated by fruit bats.

• Human-to-human

Transmission can occur through close contact with people infected with the virus, especially in healthcare settings.

4. Treatment

• No specific treatment

Currently, there is no effective treatment for Nipah virus infection. Intensive supportive care is provided to treat respiratory and neurologic complications.

• Antivirals

While not a standard treatment, the antiviral drug ribavirin has been shown to be effective against the viruses in vitro, but its clinical usefulness remains uncertain.

5. Prevention

• Avoid contact with sick animals

Especially pigs and bats in endemic regions.

• Food safety

Avoid consuming raw date palm sap or fruits that may have been contaminated by fruit bats.

• Regular handwashing

Especially after contact with sick people or animals.

• Protective measures in healthcare settings

This includes using standard precautions for all patients and additional precautions for those with suspected Nipah virus infection.

• Awareness and education

Informing the public about the nature of the disease and its transmission routes can help reduce human exposure.

• Surveillance and outbreak containment

Rapid detection and appropriate response can prevent wider spread during outbreaks.

Understanding the ecology of bats and Nipah virus infection—how the disease is transmitted between bats and how it spills over to other species and humans—can guide effective prevention measures.

17. Ringworm

1. Cause

• Ringworm, despite its name, is not caused by a worm. It’s a skin infection caused by a group of fungi. Different species of dermatophytes are responsible for infections in various parts of the body.

2. Symptoms

The appearance of ringworm can vary depending on the part of the body it affects, but general symptoms include:

• Red, scaly, and itchy patches of skin.

• Patches may blister or ooze.

• The patches often have sharply-defined edges.

• They may be redder around the outside with normal skin tone in the center, creating the appearance of a ring.

• If the scalp is affected, there might be bald patches.

3. Transmission

• Human-to-human contact

Direct skin-to-skin contact with an infected person.

• Animal-to-human contact

Direct contact with an infected animal, often a cat or dog.

• Object-to-human contact

Touching objects or surfaces that have the fungus on them, such as towels, bedding, and combs.

• Soil-to-human

In some cases, ringworm can be contracted from infected soil.

4. Treatment

• Topical antifungal creams

Most cases of ringworm can be treated with over-the-counter antifungal creams, lotions, or powders such as clotrimazole or terbinafine.

• Oral antifungal medications

For more severe or widespread infections, or for ringworm of the scalp, oral medications like griseofulvin or terbinafine may be prescribed.

5. Prevention

• Maintain hygiene

Keep skin, hair, and nails clean and dry.

• Avoid sharing

Do not share clothing, towels, hairbrushes, or other personal items with someone who has the infection.

• Wear appropriate footwear

In public places like gyms, swimming pools, and communal showers, wear sandals to prevent direct contact with the floor.

• Wash hands

After handling pets, soil, or any items that might be contaminated.

• Check pets

Regularly check pets for patches of missing fur, which might be a sign of a fungal infection, and get them treated promptly.

• Avoid tight clothing

Especially in warm or humid climates to reduce sweating and moisture, which can promote fungal growth.

While ringworm can be uncomfortable, it’s typically not serious and can be effectively treated with antifungal medications. Preventative measures can significantly reduce the risk of acquiring or spreading the infection.

18. Toxoplasmosis

1. Cause

• Toxoplasmosis is caused by the protozoan parasite Toxoplasma gondii.

2. Symptoms

Most people infected with Toxoplasma gondii are asymptomatic. However, those who do show symptoms might experience:

• Flu-like symptoms such as swollen lymph nodes or muscle aches that can last for a month or more.

• Severe toxoplasmosis, causing damage to the brain, eyes, or other organs, can develop from an acute Toxoplasma infection or one that had occurred earlier in life and is now reactivated. Severe cases are more likely in individuals who have weak immune systems, though occasionally, even persons with healthy immune systems may experience eye damage from toxoplasmosis.

• Babies born to mothers who become infected with Toxoplasma gondii during or just before pregnancy can have serious health problems, such as an enlarged or small head, hearing loss, blindness, or mental disabilities.

3. Transmission

• Consuming undercooked, contaminated meat

Especially pork, lamb, and venison.

• Ingesting the parasite

This can occur by touching your mouth after gardening, cleaning a cat’s litter box, or touching anything that has come into contact with cat feces.

• Mother-to-child transmission

If a woman becomes infected for the first time shortly before or during pregnancy, she can pass the infection to her unborn child.

• Organ transplantation or blood transfusion

Though rare, it’s possible to get toxoplasmosis from an infected organ transplant or blood transfusion.

• Laboratory transmission

Direct contact with the parasite in a lab setting.

4. Treatment

• Healthy individuals

Usually do not require treatment. Symptoms, if they appear, will typically go away within a few weeks to months.

• Pregnant women and immunocompromised individuals

Medications can help reduce the severity of symptoms and prevent complications. Commonly used medications include pyrimethamine combined with sulfadiazine.

5. Prevention

• Cook food to safe temperatures

Cooking meat thoroughly kills Toxoplasma parasites.

• Peel or wash fruits and vegetables

This ensures they are free from soil that might be contaminated.

• Avoid untreated water

Toxoplasma can be found in untreated water.

• Practice good hygiene

Wash your hands thoroughly with soap and warm water after handling soil, gardening, or cleaning a cat’s litter box.

• Avoid cleaning cat litter

If possible, especially for pregnant women. If it’s unavoidable, wear disposable gloves and wash hands thoroughly afterward. Ensure the litter box is cleaned daily since the Toxoplasma parasite does not become infectious until 1 to 5 days after it’s shed in the feces.

• Keep outdoor sandboxes covered

Cats may use them as litter boxes.

• Cat Food

Feed cats only canned or dried commercial food or well-cooked table food and not raw or undercooked meats.

Awareness of the sources of infection and practicing appropriate preventive measures can significantly reduce the risk of acquiring toxoplasmosis.

19. Bovine Tuberculosis

1. Cause

• Bovine tuberculosis is caused by the bacterium Mycobacterium bovis (M. bovis), which is closely related to the bacterium that causes human tuberculosis (Mycobacterium tuberculosis).

2. Symptoms

In cattle

• Persistent cough

• Weight loss

• Reduced appetite

• Fever

• Enlarged lymph nodes

In humans

• Persistent cough, sometimes with blood

• Weight loss

• Fever

• Night sweats

• Fatigue

3. Transmission

• Cattle to cattle

Via respiratory secretions, when they are in close contact with each other.

• From infected animals to humans

Mainly through the ingestion of unpasteurized milk or dairy products from infected cows. Direct contact with a wound or the inhalation of the bacteria (e.g., during slaughter) can also be sources of transmission.

• Wildlife reservoirs

Some wild animals, such as badgers and deer, can also be reservoirs of M. bovis and can transmit the disease to cattle or humans.

4. Treatment

• In cattle

Infected cattle are often culled to control the spread of the disease. Culling is the primary method of control rather than treatment due to concerns about antibiotic resistance, economic implications, and public health risks.

• In humans

Treatment is similar to human TB, involving a combination of antibiotics for many months. The exact regimen may vary depending on drug susceptibility testing.

5. Prevention

• Regular Testing of Cattle Herds

Using the tuberculin skin test or gamma interferon test helps identify and cull infected animals.

• Controlled Movement of Cattle

Cattle from infected herds should not be moved to areas with uninfected herds.

• Pasteurization of Milk

This process kills M. bovis, reducing the risk of transmission to humans from dairy products.

• Education and Training

Farmers, veterinarians, and slaughterhouse workers should be informed about the risks and precautions to take when handling potentially infected animals.

• Protective Clothing and Equipment

For individuals at risk of exposure, like veterinarians and slaughterhouse workers.

• Wildlife Control

In areas where wildlife reservoirs are a known risk, strategies might include reducing the population of the reservoir species, preventing contact between wildlife and cattle, and vaccinating wildlife.

It’s crucial to have stringent surveillance and control measures in place to limit the spread of bovine TB, given its economic impact on the farming industry and its potential health implications for humans.

20. Monkeypox

1. Cause

• Monkeypox is a viral disease caused by the monkeypox virus. It’s similar to human smallpox, although it’s typically milder.

2. Symptoms

The illness begins with:

• Fever

• Headache

• Muscle aches

• Backache

• Swollen lymph nodes

• Chills

• Exhaustion

A rash then develops, often beginning on the face and then spreading to other parts of the body. The rash changes and progresses to pustules before finally scabbing over and falling off.

3. Transmission

• Direct contact with animals

It can be transmitted to humans from animals (rodents are a major reservoir, but monkeys and other primates can also harbor the virus).

• Consumption of contaminated meat

Eating undercooked meat of infected animals can also spread the virus.

• Human-to-human transmission

While it’s less common, the virus can spread from one person to another through respiratory droplets, direct contact with body fluids, or contaminated materials.

4. Treatment

• No specific treatment

There’s no definitive cure for monkeypox. Treatment is primarily supportive and might include measures to control fever, hydration, and treatment of secondary infections.

• Smallpox vaccination

Historically, the smallpox vaccine has been used post-exposure to prevent the disease or reduce the severity of symptoms. However, with smallpox eradication and the subsequent cessation of routine smallpox vaccination, this option is less available.

5. Prevention

• Avoiding contact with animals

Especially those that could harbor the virus.

• Avoid undercooked meat

Avoid consuming undercooked meat, particularly bushmeat.

• Isolation of symptomatic patients

To reduce the risk of human-to-human transmission.

• Use of personal protective equipment

Healthcare workers and those caring for infected patients or handling potentially contaminated materials should use appropriate protective gear.

• Hand hygiene

Regular washing of hands with soap and water or using a hand sanitizer.

• Public health education

Informing communities about the virus, its transmission routes, and methods of prevention can help reduce human exposure.

Prompt detection and rapid response through surveillance, lab confirmation, and the institution of control measures are crucial to preventing further spread during outbreaks.

21. African Swine Fever

1. Cause

• African Swine Fever is caused by the African Swine Fever virus (ASFV). It’s a highly contagious and usually fatal viral disease affecting domestic and wild pigs.

2. Symptoms

Symptoms in swine include:

• High fever

• Decreased appetite

• Red/blotchy skin patches

• Diarrhea and vomiting

• Coughing and difficulty breathing

• Swollen eyes

• Miscarriages in pregnant sows

• Sudden death in severe cases

3. Transmission

• Direct contact

Between sick and healthy pigs.

• Indirect contact

Via equipment, vehicles, feed, clothing, and shoes that have been contaminated.

• Vector-borne

Certain species of ticks can transmit the virus.

• Wild reservoirs

Wild boar can be a source of infection for domestic pigs.

• Pork products

Contaminated feed or undercooked contaminated pork products can spread the disease.

4. Treatment

• No specific treatment

There is currently no approved vaccine against ASF, and there’s no cure. The main approach to controlling ASF is to cull infected or susceptible animals.

5. Prevention

• Biosecurity measures

This includes limiting visitors on pig farms, changing clothing and shoes before entering pig pens, and regularly cleaning and disinfecting equipment and facilities.

• Control movement

Restrict movement of pigs from and to areas known to have ASF.

• Safe disposal

Properly dispose of waste food, especially pork products, to prevent feeding to pigs.

• Vector control

Manage tick populations in areas where they are known vectors of ASFV.

• Surveillance

Regularly monitor swine populations for symptoms and act promptly if there is any suspicion of ASF.

• Education

Ensure that pig farmers and swine workers are aware of the signs and symptoms of ASF and the steps they can take to prevent its spread.

ASF is of significant economic concern, given its devastating impact on swine populations and the subsequent implications for the pork industry. Preventing its spread is crucial, especially since there’s currently no vaccine or cure.

22. Campylobacteriosis

1. Cause

Campylobacteriosis is caused by bacteria belonging to the genus Campylobacter, with Campylobacter jejuni being the most common species causing illness in humans.

2. Symptoms

The disease manifests as a gastrointestinal infection with symptoms including:

• Diarrhea (which can be bloody)

• Abdominal pain and cramping

• Fever

• Nausea and vomiting

• Malaise

• Headache

The symptoms typically last about a week, but some individuals might experience complications like dehydration or, more rarely, post-infectious conditions like Guillain-Barré syndrome, a serious condition that affects the nervous system.

3. Transmission

• Undercooked poultry

Consuming undercooked chicken or other poultry is a common route of transmission.

• Contaminated food or water

Ingestion of food or water contaminated with the bacteria.

• Direct contact

Handling raw poultry or having contact with feces of infected animals, especially puppies and kittens.

• Person-to-person

Though less common, infected individuals can pass it to others through the fecal-oral route.

4. Treatment

• Rehydration

It’s essential to replace lost fluids due to diarrhea.

• Antibiotics

For severe cases or for those at high risk of complications, antibiotics like erythromycin or azithromycin may be prescribed. However, increasing resistance to certain antibiotics is a concern.

• Rest and supportive care

In most cases, rest and maintaining hydration are sufficient for recovery.

5. Prevention

• Cook poultry thoroughly

Chicken and other poultry should be cooked to a safe minimum internal temperature.

• Avoid cross-contamination

Use separate cutting boards and utensils for raw poultry and other foods, or wash them thoroughly between uses.

• Hand hygiene

Wash hands frequently, especially after handling raw meats, and before eating or preparing food.

• Safe water

Drink only water from safe sources. When unsure, boil or purify water before drinking.

• Avoid unpasteurized dairy products

These can be a source of contamination.

• Proper handling of pets

Wash hands after handling pets, especially when cleaning up their waste.

Awareness and adherence to food safety guidelines are paramount in preventing campylobacteriosis, given that contaminated food, especially poultry, is a significant source of infection.

23. Chikungunya

1. Cause

• Chikungunya is a viral disease caused by the Chikungunya virus, which belongs to the alphavirus genus.

2. Symptoms

Typically, symptoms appear 3–7 days after being bitten by an infected mosquito and can include:

• Fever

• Severe joint pain (often in hands and feet)

• Muscle pain

• Headache

• Nausea

• Fatigue

• Rash

While symptoms usually resolve within a week, joint pain can be severe and sometimes persists for months or even years. Some individuals may develop eye, neurological, or heart complications.

3. Transmission

• Mosquitoes

The primary vectors are mosquitoes, especially the Aedes aegypti and Aedes albopictus species, which bite mainly during the day.

• Blood transfusion

There have been rare cases of transmission through blood transfusion, but this is not a common route.

4. Treatment

• No specific antiviral treatment

Chikungunya treatment is aimed at relieving symptoms.

• Rest and hydration

These are essential for recovery.

• Pain relievers

Medications like acetaminophen or paracetamol can be used to reduce fever and alleviate pain. Aspirin and non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided until dengue can be ruled out to reduce the risk of hemorrhage.

5. Prevention

• Mosquito avoidance

This is the primary prevention strategy. Wearing long-sleeved shirts, pants, using insect repellents containing DEET, picaridin, or oil of lemon eucalyptus, and using bed nets can help.

• Eliminate mosquito breeding sites

This includes emptying, covering, or treating any items that hold water, like buckets, flower pots, or tires.

• Stay in air-conditioned or well-screened housing

Stay in air-conditioned or well-screened housing to minimize exposure to mosquitoes.

• Community-based integrated mosquito control

Implementing strategies to reduce mosquito populations and interrupt transmission.

• Travel awareness

If traveling to or living in an area where Chikungunya is present, take appropriate precautions to avoid mosquito bites.

Vaccines for Chikungunya are being developed and tested, but as of my last update in January 2022, none had been approved for general use.

24. Crimean-Congo Hemorrhagic Fever (CCHF)

1. Cause

• CCHF is caused by the Crimean-Congo Hemorrhagic Fever virus (CCHFV), which belongs to the Nairovirus genus.

2. Symptoms

The onset of CCHF is sudden, with initial signs and symptoms including:

• Fever

• Muscle aches

• Dizziness

• Neck pain and stiffness

• Backache

• Headache

• Sore eyes

• Photophobia (sensitivity to light)

• Nausea and vomiting

• Diarrhea

• Abdominal pain

• Sore throat

• Mood swings and confusion

Later on, mood instability, aggressive behavior, and other neurological signs may present. In severe cases, petechiae (pinpoint red spots), ecchymoses (larger areas of bleeding), and other hemorrhagic manifestations can develop, which can lead to multi-organ failure.

3. Transmission

• Ticks

The primary vector is the Hyalomma tick.

• Animal contact

Direct contact with the blood or tissues of infected animals, especially livestock.

• Human-to-human

Transmission can occur through close contact with the blood, secretions, organs, or other bodily fluids of infected persons, or from contaminated medical or burial procedures.

4. Treatment

• Supportive care

There’s no specific antiviral treatment for CCHF. Treatment is supportive and includes rehydration, management of fever, and transfusion of blood products if necessary.

• Antiviral drugs

Ribavirin has been used in some cases, but its efficacy remains a matter of debate.

5. Prevention

• Avoid tick bites

When in areas where CCHF is endemic, use repellents, wear light-colored clothing to see ticks more easily, and inspect the body regularly for ticks.

• Wear protective clothing

For those working with livestock or in healthcare settings, wearing gloves and other protective equipment can prevent transmission.

• Safe handling and cooking of animal products

Meat should be cooked thoroughly. Handle raw meat with gloves and wash hands regularly.

• Quarantine of livestock

Animals brought into endemic areas should be kept separate and regularly checked for ticks.

• Disinfection

Regularly clean and disinfect instruments and equipment, especially in healthcare settings.

Raising awareness in at-risk communities and training for healthcare workers can also be instrumental in preventing and controlling CCHF outbreaks. As of my last update in January 2022, there was ongoing research for a vaccine, but none had been approved for widespread use.

25. Cryptosporidiosis

1. Cause

• Cryptosporidiosis is an intestinal disease caused by the microscopic parasite Cryptosporidium. Multiple species can infect humans, with Cryptosporidium hominis and Cryptosporidium parvum being the most common.

2. Symptoms

Symptoms usually appear 2 to 10 days after infection and can include:

• Watery diarrhea

• Stomach cramps or pain

• Dehydration

• Nausea

• Vomiting

• Fever

• Weight loss

In immunocompetent individuals, symptoms generally last 1 to 2 weeks. However, for those with weakened immune systems, such as AIDS patients or those undergoing chemotherapy, the illness can be severe and prolonged, sometimes leading to life-threatening complications.

3. Transmission

• Fecal-oral route

Consuming food or water contaminated with feces from an infected human or animal.

• Recreational water

Swimming in pools, hot tubs, or natural bodies of water that are contaminated. The parasite can survive for long periods in chlorine-treated water.

• Person-to-person

Transmission can occur via direct contact with an infected individual or contaminated surfaces.

• Animal contact

Handling infected animals or their feces.

4. Treatment

• Rehydration

Drink plenty of fluids to avoid dehydration due to diarrhea.

• Anti-parasitic drugs

For otherwise healthy adults, the illness is usually self-limiting. However, in severe or prolonged cases or for those with weakened immune systems, nitazoxanide may be prescribed.

5. Prevention

• Water precautions

Boil or filter water if there’s a risk of contamination. This is especially important when traveling in areas with poor sanitation.

• Hand hygiene

Wash hands thoroughly with soap and water after using the restroom, before eating, after handling animals, and after changing diapers.

• Avoid swallowing water when swimming

Especially in pools, lakes, rivers, or other recreational water sources.

• Food safety

Wash and cook food properly. Be cautious of raw foods in areas with known contamination.

• Limit animal contact

Particularly for young children and animals known to be shedding the parasite.

Understanding the importance of proper sanitation and taking preventive measures can significantly reduce the risk of cryptosporidiosis, especially in areas where the parasite is endemic or during outbreaks.

26. Echinococcosis

1. Cause

• Echinococcosis, also known as hydatid disease, is caused by the larvae of tapeworms belonging to the genus Echinococcus. The two main types are cystic echinococcosis, caused by Echinococcus granulosus, and alveolar echinococcosis, caused by Echinococcus multilocularis.

2. Symptoms

Symptoms depend on the location and size of the cyst. The disease often remains asymptomatic for years until the cysts grow large enough to cause discomfort or complications. Depending on the organ affected, symptoms can include:

• Abdominal pain

• Nausea and vomiting

• Cough

• Chest pain

• Jaundice (if the liver is affected)

Complications might involve rupture of the cysts, leading to anaphylactic reactions, or secondary bacterial infections.

3. Transmission

• Fecal-oral route

Ingesting tapeworm eggs shed in the feces of infected definitive hosts, usually dogs for E. granulosus and foxes for E. multilocularis.

• Consumption of contaminated food

Ingesting food, especially vegetables and fruits, contaminated with feces from an infected host.

• Direct contact with infected animals

Avoid contact with infected animals, especially when handling or grooming.

4. Treatment

• Surgery

Removal of the cysts surgically is often the primary treatment, especially for large or complicated cysts.

• Anti-parasitic drugs

Albendazole and mebendazole can be used to treat the disease, especially for inoperable cases or to shrink cysts before surgery.

• Percutaneous treatments

In some cases, cysts can be drained or treated using minimally invasive techniques guided by imaging.

5. Prevention

• Regular deworming of dogs

Especially in endemic areas, to prevent them from becoming sources of infection.

• Safe slaughtering practices

Proper inspection and disposal of organs showing cysts can prevent the spread.

• Hygiene practices

Washing hands regularly, especially after handling animals or soil, and before eating.

• Safe food practices

Washing vegetables and fruits thoroughly before consumption, and avoiding consumption of food in areas where the disease is endemic without proper precautions.

• Public Education

Raising awareness in at-risk communities about the life cycle of the parasite and how the disease spreads.

Regular veterinary public health interventions and collaborations between human health and animal health sectors can also be effective in controlling and reducing the transmission of echinococcosis.

27. Giardiasis

1. Cause

• Giardiasis is an intestinal infection caused by the protozoan parasite Giardia lamblia (also known as Giardia intestinalis or Giardia duodenalis).

2. Symptoms

Symptoms usually appear 1 to 3 weeks after exposure and can include:

• Diarrhea

• Gas or flatulence

• Greasy stools that float

• Stomach or abdominal cramps

• Upset stomach or nausea

• Dehydration

• Fatigue

Some infected individuals might remain asymptomatic but can still spread the disease.

3. Transmission

• Fecal-oral route

Ingesting the parasite from contaminated food or water sources.

• Person-to-person

Especially among children in daycare centers or people in close living conditions.

• Animal-to-person

Contact with infected animals or their environment.

• Recreational water

Swimming in contaminated pools, lakes, or rivers.

4. Treatment

• Antiprotozoal medications

The most commonly prescribed drugs are metronidazole (Flagyl) and tinidazole (Tindamax). Nitazoxanide (Alinia) can be used in certain cases, especially for children.

5. Prevention

• Water precautions

Use filtered, boiled, or bottled water, especially in areas where giardiasis is common or if the source is uncertain.

• Hand hygiene

Wash hands thoroughly with soap and water after using the restroom, changing diapers, before eating, or after handling animals.

• Safe food practices

Avoid raw or undercooked food in areas where the disease is endemic. Wash and peel fruits and vegetables before eating.

• Avoid swallowing recreational water

Especially in pools, lakes, or rivers.

• Travel precautions

When traveling to areas where giardiasis is prevalent, consume only bottled or boiled water and avoid ice cubes or raw foods.

Educating at-risk populations and improving sanitation and water quality can significantly reduce the incidence of giardiasis.

28. Japanese Encephalitis

1. Cause

• Japanese Encephalitis is a viral disease caused by the Japanese Encephalitis virus (JEV). The virus belongs to the Flavivirus genus and is related to West Nile, dengue, and yellow fever viruses.

2. Symptoms

Most people infected with JEV have either no symptoms or only mild symptoms. However, a small fraction can develop severe clinical illness. Symptoms typically begin 5-15 days after being bitten by an infected mosquito and can include:

• High fever

• Headache

• Neck stiffness

• Disorientation

• Coma

• Tremors

• Seizures (especially in children)

• Muscle weakness or paralysis

Severe cases can lead to death or long-term neurological complications.

3. Transmission

• Mosquitoes

JE is primarily transmitted to humans through the bite of infected Culex species mosquitoes. The mosquitoes become infected by feeding on infected pigs or wild birds.

• Important to note

JE does not spread from person to person.

4. Treatment

• There is no specific antiviral treatment for JE. Management is supportive and can involve hospitalization, respiratory support (mechanical ventilation), pain relievers, and management of fever and seizures.

• Severe infections may require intensive supportive therapy.

5. Prevention

• Vaccination

Safe and effective JE vaccines are available, and immunization is the most effective preventive measure.

• Mosquito protection

  • Use of mosquito nets and screens.
  • Wearing long-sleeved clothing and trousers.
  • Applying insect repellents containing DEET or other effective ingredients.
  • Limiting outdoor activities during peak mosquito-biting hours (dusk and dawn)

• Vector control

This includes measures to control mosquito breeding, like reducing sources of standing water where mosquitoes breed.

• Pig management

Since pigs are amplifying hosts, keeping them away from human dwellings and vaccinating them can help reduce the risk.

Travelers to JE-endemic areas (parts of East and Southeast Asia and the western Pacific) should consider vaccination, especially if they plan to spend prolonged periods outdoors or in rural areas. It’s always a good idea to consult with travel medicine specialists before visiting areas where JE is endemic.

29. Lassa Fever

1. Cause

• Lassa Fever is caused by the Lassa virus, an arenavirus.

2. Symptoms

Symptoms usually appear 1-3 weeks after the individual comes into contact with the virus. Many infected people have mild symptoms or none at all. However, for those who develop symptomatic disease, the following may be observed:

• Fever

• Fatigue

• Weakness

• Headache

• Sore throat

• Cough

• Nausea

• Vomiting

• Diarrhea

• Chest and abdominal pain

• In severe cases: facial swelling, fluid in the lung cavity, bleeding from mouth, nose, vagina, or gastrointestinal tract, and shock.

Death may occur 10-14 days after the onset of symptoms in severe cases.

3. Transmission

• Rodent reservoir

The primary host of the Lassa virus is the Natal multimammate mouse (Mastomys natalensis). Humans can become infected from direct contact with the urine or feces of the mouse.

• Person-to-person

Through direct contact with the blood, tissue, urine, or feces of an infected person, especially in healthcare settings without proper protective equipment.

• Consumption

Eating infected rodents or food contaminated by rodents.

4. Treatment

• Supportive care

Rehydration, pain management, maintaining proper oxygen status and blood pressure, and treating other infections that may develop.

• Antiviral medication

Ribavirin has been found to be effective when administered early in the course of the illness.

5. Prevention

• Community hygiene

Proper storage of grain and other foodstuffs to prevent rodent contamination.

• Keeping the home clean

This can deter rodents from entering homes.

• Safe handling

Protective measures such as wearing gloves, masks, and gowns when handling or caring for patients suspected of having Lassa Fever.

• Safe burial practices

Due to the potential for transmission through contact with the deceased.

• Rodent control

Measures to control the rodent population in residential areas.

• Education

Raising awareness in communities about the risks of the disease and how to prevent its spread.

It’s worth noting that outbreaks of Lassa Fever have been observed primarily in West Africa, with Nigeria, Liberia, Sierra Leone, and Guinea being the most affected countries.

30. Marburg Virus Disease

1. Cause

• Marburg Virus Disease (MVD) is caused by the Marburg virus, a member of the Filoviridae family. It’s closely related to the Ebola virus.

2. Symptoms

The onset of the disease is sudden, with symptoms appearing between 2 and 21 days after infection. They include:

• Fever

• Severe headache

• Joint and muscle aches

• Chills

• Weakness

• Fatigue

As the disease progresses, it can lead to:

• Nausea

• Vomiting

• Chest pain

• Sore throat

• Abdominal pain

• Diarrhea

In severe cases, it can cause:

• Jaundice

• Pancreatitis

• Weight loss

• Delirium

• Shock

• Organ failure

• Hemorrhagic symptoms, including bleeding from the eyes, ears, nose, and mouth.

3. Transmission

• Animal to human

The exact reservoir of the Marburg virus is not completely known, but fruit bats, especially the Rousettus bat, are considered to be the natural host. Humans can be infected by handling ill or dead animals.

• Human to human

The virus spreads between humans through close contact with the blood, secretions, organs, or other bodily fluids of infected persons. It can also spread through contact with surfaces and materials contaminated with these fluids.

4. Treatment

• Supportive care

This includes rehydration with oral or intravenous fluids and treatment of specific symptoms. Maintaining oxygen status, blood pressure, and treating any complicating infections are crucial.

• Medication

No approved drug for treating MVD currently exists, but various experimental treatments are under investigation.

5. Prevention

• Avoiding contact with bats

Particularly in caves or mines in areas where Marburg is known to occur.

• Protective measures for healthcare workers

This involves wearing protective clothing and following infection prevention and control protocols.

• Safe burial practices

Using appropriate measures for deceased individuals suspected or confirmed to have MVD.

• Rapid containment strategies

This includes swiftly identifying cases, contact tracing, and isolating patients to prevent further transmission.

• Health education

Informing the public about the disease, its reservoirs, and how to protect themselves.

There’s currently no licensed vaccine against MVD, but several experimental vaccines are in the stages of development and testing.

31. Psittacosis (Ornithosis)

1. Cause

• Psittacosis, also known as parrot fever or ornithosis, is caused by the bacterium Chlamydia psittaci.

2. Symptoms

Symptoms generally manifest 5 to 14 days after exposure and can include:

• Fever and chills

• Headache

• Muscle aches

• Dry cough

• Fatigue

• Shortness of breath

• Chest pain

• Nausea, vomiting, and diarrhea (less common)

The disease can range from mild to severe, and in some cases, severe pneumonia or even systemic infection can develop.

3. Transmission

• Bird to human

The primary source of infection is birds, particularly parrots, parakeets, macaws, and cockatiels, but also pigeons, ducks, and many other species. Humans can get infected by inhaling the bacterium from dried droppings, respiratory secretions, or feather dust of infected birds.

• Direct contact

Handling an infected bird or its secretions can also lead to transmission.

• It’s important to note

Human-to-human transmission is extremely rare.

4. Treatment

• Antibiotics

Doxycycline is the first choice of treatment for adults and older children. In younger children and pregnant women, macrolide antibiotics like azithromycin might be used.

5. Prevention

• Regular bird screening

Regularly testing pet birds, especially new acquisitions or birds that participate in shows, can help identify and treat potential carriers.

• Isolation

Newly acquired or sick birds should be isolated from other birds.

• Cleanliness

Regularly cleaning bird cages and using gloves and masks when handling birds or cleaning their environments can reduce the risk of inhaling the bacteria.

• Ventilation

Ensuring good ventilation in places where birds are kept can reduce the concentration of the bacterium in the air.

• Education

Bird owners, breeders, and sellers should be made aware of the risks of psittacosis and how to prevent its transmission.

If someone has been exposed to an infected bird or develops symptoms after contact with birds, they should seek medical advice promptly.

32. Rift Valley Fever (RVF)

1. Cause

• Rift Valley Fever is caused by the Rift Valley Fever virus (RVFV), which belongs to the Phlebovirus genus.

2. Symptoms

The majority of human infections are asymptomatic or result in a mild illness. When symptoms do appear (usually 2-6 days after exposure), they can include:

• Sudden onset of fever

• Muscle pain

• Joint pain

• Headache

• Nausea and vomiting

In more severe cases, complications can develop, such as:

• Hemorrhagic fever: bleeding and blood clotting abnormalities

• Encephalitis: inflammation of the brain, leading to seizures, coma, and even death

• Eye disease: retinal lesions and vision loss

3. Transmission

• Mosquitoes

The primary mode of transmission is through the bite of infected Aedes and Culex mosquitoes.

• Direct contact

Humans can get infected by direct or indirect contact with the blood or organs of infected animals, especially during slaughtering.

• Consumption

Drinking raw milk from infected animals.

• Airborne

There’s some evidence to suggest the virus can be transmitted in aerosols under certain circumstances, especially in the laboratory setting.

4. Treatment

• Supportive care

Currently, there is no specific treatment for RVF. Patients often require supportive therapy, which can include rehydration, pain relief, and treatment for any complications.

• Antiviral medication

Some antiviral medications might be effective, but their role in treating RVF remains uncertain.

5. Prevention

• Vaccination

There are vaccines available for livestock, which can help control the spread of the disease to humans.

• Mosquito control

Reducing mosquito populations and avoiding mosquito bites (using repellents, bed nets, and wearing long-sleeved clothing).

• Safe animal handling

Using protective equipment when handling animals, especially during slaughtering or when dealing with potentially infected tissue.

• Avoiding raw milk

Boiling milk before consumption.

• Public Education

Educating communities about the risks and prevention methods.

It’s important to note that RVF outbreaks often follow periods of heavy rainfall and flooding, which increase mosquito populations. Monitoring and surveillance in these conditions can help in early detection and management of outbreaks.

33. Ross River Virus

1. Cause

Ross River Virus is an arbovirus that causes a disease often referred to as Ross River Fever or Epidemic Polyarthritis.

2. Symptoms

Symptoms typically appear between 7 to 9 days after being bitten by an infected mosquito, but this can range from 3 to 21 days. They include:

• Joint pain and swelling, which can last weeks to months

• Muscle pain or tenderness

• Fatigue

• Fever and chills

• Rash, typically on the trunk or limbs (usually non-itchy)

• Enlarged or tender lymph nodes

Many people infected with RRV have mild symptoms or none at all. However, symptoms can be debilitating, and some people may remain symptomatic for a year or more.

3. Transmission

• Mosquitoes

RRV is primarily transmitted to humans through the bite of infected mosquitoes. The primary vectors are believed to be the Aedes vigilax, Aedes notoscriptus, and Culex annulirostris mosquitoes.

• Animal reservoirs

Various animals, including kangaroos and wallabies, can act as reservoirs of the virus. Mosquitoes acquire the virus by feeding on these infected animals.

4. Treatment

• Symptomatic relief

There’s no specific antiviral treatment for RRV. Management primarily involves relieving symptoms. Pain and inflammation can be managed with analgesics such as paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs).

• Physical activity

Gradual and regular physical activity can help manage joint pain and stiffness.

• Rest

Adequate rest is crucial, especially during the acute phase of the illness.

5. Prevention

• Mosquito control

Reducing mosquito populations through environmental management, such as eliminating stagnant water where mosquitoes breed.

• Personal protection

Using mosquito repellents, wearing long-sleeved clothing, and using bed nets in areas where the virus is prevalent.

• Awareness

Local health authorities may issue warnings during times of increased RRV activity, especially after heavy rains or in areas with significant mosquito breeding sites.

Ross River Virus is primarily found in Australia and the Pacific Islands. While anyone can get infected, those living in or traveling to endemic regions are at greater risk.

34. Schistosomiasis

1. Cause

• Schistosomiasis is caused by parasitic flatworms known as schistosomes. The major species affecting humans are Schistosoma mansoni, S. haematobium, and S. japonicum.

2. Symptoms

Symptoms of schistosomiasis are due to the body’s reaction to the worms’ eggs. They vary depending on the species of worm and stage of infection.

• Acute phase (Katayama fever)

Appears weeks after initial infection and can include:

• • Fever and chills
• • Cough
  • Muscle aches
  • Fatigue
  • Diarrhea
  • Abdominal pain

• Chronic phase

Can lead to complications involving the organs the eggs are lodged in, such as:

• • Liver enlargement (with S. mansoni and S. japonicum)
  • Blood in the stool or urine
  • Problems with the bladder, kidneys, or liver
  • Intestinal damage or bleeding
  • Pulmonary hypertension (rarely)
  • Bladder cancer (with chronic S. haematobium infection)

3. Transmission

• Freshwater snails

The larvae of the schistosomes are released by infected freshwater snails. Humans get infected when skin comes in contact with freshwater contaminated by these larvae.

• Human contamination

Infected individuals release schistosome eggs in their urine or feces. If this reaches freshwater, it can infect snails, completing the life cycle.

4. Treatment

• Praziquantel

This is the drug of choice for treating schistosomiasis. The duration and dosage vary depending on the specific species causing the infection.

• Supportive care

Managing complications and symptoms, such as pain relief for liver complications or surgical intervention for severe cases.

5. Prevention

• Avoid freshwater contact

Avoid freshwater contact in areas known to have schistosomiasis. This is the most effective prevention method for travelers.

• Water treatment

Boiling or chemically treating water before use can kill the larvae.

• Snail control

Reducing the snail population can decrease the transmission of the parasite.

• Improved sanitation

Proper disposal of human waste can prevent the contamination of water sources.

• Health education

Educating communities about the risks and how to prevent transmission.

• Mass Drug Administration (MDA)

In endemic areas, periodic treatment of at-risk populations with praziquantel can reduce the disease burden.

Schistosomiasis is especially prevalent in tropical and subtropical areas, particularly in poor communities without access to safe drinking water and adequate sanitation.

35. Trichinellosis

1. Cause

• Trichinellosis is caused by nematodes (roundworms) of the genus Trichinella. The most common species that infects humans is Trichinella spiralis.

2. Symptoms

The symptoms of trichinellosis vary depending on the stage of infection and the number of encysted larvae consumed. They can include:

• Intestinal phase

(about 1-2 days after ingestion)

• • Diarrhea
  • Abdominal pain
  • Nausea
  • Vomiting
  • Fatigue

• Muscular phase

(about 2 weeks after ingestion)

• • Muscle pain and tenderness
  • Swelling of the eyelids or face
  • Fever
  • Weakness
  • Headache
  • Sensitivity to light and pink eye (conjunctivitis)
  • Difficulty coordinating movements

In severe cases, complications such as myocarditis, encephalitis, and respiratory failure can occur.

3. Transmission

• Consuming infected meat

Humans typically become infected when they eat undercooked or raw meat containing the encysted larvae of Trichinella. Pork and wild game meat are the most common sources of human infections.

• Animal-to-animal

Carnivorous and omnivorous animals can become infected when they eat the meat of other infected animals.

4. Treatment

• Antiparasitic medication

Albendazole or mebendazole can be used to treat trichinellosis. They work best when administered early in the infection.

• Pain relief

Over-the-counter pain relievers can help alleviate muscle pain and inflammation.

• Steroids

In severe cases, corticosteroids may be prescribed to manage inflammation.

5. Prevention

• Cooking meat thoroughly

Meat should be cooked to an internal temperature of at least 160°F (71°C) and frozen for a specified period, especially if it’s wild game or pork.

• Avoiding raw or undercooked meat

Especially in areas where trichinellosis is common.

• Safe meat handling

Use separate cutting boards for raw meat and other foods, and wash hands thoroughly after handling raw meat.

• Proper pig farming practices

Ensuring pigs are raised in clean conditions and are not given raw meat or scraps can reduce the risk of them becoming infected.

• Freezing

Freezing meat can kill some, but not all species of Trichinella. For example, freezing is effective against T. spiralis in pork but not against species typically found in wild game.

• Education

Making sure hunters and the general public are aware of the risks and know how to properly cook and handle meat.

It’s worth noting that the incidence of trichinellosis has significantly decreased in many parts of the world due to stricter regulations on pork production and public education on the risks of consuming undercooked meat.

36. Trypanosomiasis (Sleeping sickness)

1. Cause

• African trypanosomiasis, commonly known as sleeping sickness, is caused by the protozoan parasites Trypanosoma brucei gambiense (causing West African sleeping sickness) and Trypanosoma brucei rhodesiense (causing East African sleeping sickness).

2. Symptoms

Symptoms are presented in stages:

• First stage (Hemolymphatic stage)

  • Fever
  • Fatigue
  • Joint pain
  • Swelling in the back of the neck (Winterbottom’s sign, especially in West African form)
  • Enlarged lymph nodes
  • Headache
  • Itching

• Second stage (Neurological stage)

  • Disturbed sleep patterns (sleeping during the day, awake at night)
  • Coordination problems and tremors
  • Personality changes, mood swings
  • Confusion and difficulty concentrating
  • Severe neurological disorders, including paralysis
  • If untreated, this stage can lead to coma and death

3. Transmission

• Tsetse fly bite

The disease is transmitted to humans through the bite of an infected tsetse fly, which is found primarily in rural Africa.

• Animal reservoirs

Both forms of the parasite have reservoirs in wild and domestic animals, making eradication efforts challenging.

4. Treatment

The treatment depends on the stage of the disease:

• First stage

  • For T.b. gambiense: Pentamidine
  • For T.b. rhodesiense: Suramin

• Second stage

  • For T.b. gambiense: Eflornithine or a combination of Eflornithine and nifurtimox
  • For T.b. rhodesiense: Melarsoprol (though it has serious side effects)

5. Prevention

• Vector control

Reducing tsetse fly populations using traps, insecticides, and clearing vegetation.

• Regular screenings

In endemic areas, regular medical screenings can help detect and treat the disease early.

• Protective clothing

Wearing long-sleeved clothing can minimize the exposure to tsetse flies.

• Insect repellent

Although repellents are not as effective against tsetse flies as they are against mosquitoes, they can still offer some protection.

• Awareness and education

Informing travelers and residents in endemic areas about the risks of sleeping sickness and the importance of seeking early treatment.

African trypanosomiasis has been targeted for elimination. With continued efforts, the number of cases has substantially reduced in recent years. However, without ongoing surveillance and control measures, there’s a risk of resurgence.

37. Tularemia

1. Cause

• Tularemia, also known as rabbit fever or deer fly fever, is caused by the bacterium Francisella tularensis.

2. Symptoms

The symptoms of tularemia vary depending on the route of infection:

• Ulceroglandular

  • Skin ulcer at the site of infection
  • Swollen and painful lymph glands
  • Fever, chills, and fatigue

• Glandular

• Oculoglandular

  • Eye irritation and inflammation
  • Discharge
  • Swollen lymph glands in front of the ear

• Oropharyngeal

  • Throat pain
  • Mouth ulcers
  • Swollen and painful lymph glands
  • Vomiting and diarrhea

• Pneumonic

  • Dry cough
  • Chest pain
  • Difficulty breathing

• Typhoidal

  • Fever
  • Fatigue
  • Weakness
  • Enlarged liver and spleen

3. Transmission

• Direct contact

Handling infected animals, especially rabbits, hares, and rodents.

• Insect bites

From ticks and deer flies.

• Inhalation

Breathing in dust or aerosols contaminated with the bacteria.

• Ingestion

Consuming contaminated food or water.

• Biological vectors

It’s also worth noting that F. tularensis has been considered a potential bioterrorism agent.

4. Treatment

• Antibiotics

Streptomycin and gentamicin are first-line treatments. Doxycycline and ciprofloxacin can also be effective.

• Treatment

Early detection and treatment are crucial, as the disease can be severe and sometimes fatal if left untreated.

5. Prevention

• Avoid contact

Don’t handle sick or dead animals, especially rabbits, hares, and rodents.

• Protective clothing

Wear gloves and long sleeves when hunting or handling animals.

• Insect protection

Use insect repellent and wear long-sleeved clothing to reduce the risk of tick and deer fly bites.

• Cook meat thoroughly

Ensure that wild game meat is cooked thoroughly before consumption.

• Avoid untreated water

Don’t drink, wash, or bathe in untreated water from ponds or streams where the bacteria might be present.

• Vaccination

A vaccine is in development but is not widely available to the general public as of my last training cut-off in 2022.

Public health education and surveillance are crucial in areas where tularemia is endemic. Regularly monitoring wildlife populations and tick vectors can help detect outbreaks early and inform control measures.

38. Yellow Fever

1. Cause

Yellow fever is caused by the yellow fever virus, which is a member of the flavivirus group.

2. Symptoms

The symptoms of yellow fever appear after an incubation period of 3 to 6 days and are divided into two phases:

• Acute phase

  • Sudden onset of fever
  • Chills
  • Severe headache
  • Back pain
  • General body aches
  • Nausea and vomiting
  • Fatigue
  • Weakness

Most patients improve after this phase.

• Toxic phase

(for the small percentage of patients whose symptoms progress):

• • Recurrence of high fever
  • Jaundice (yellowing of the skin and eyes, hence the name “yellow fever”)
  • Dark urine
  • Abdominal pain with vomiting
  • Bleeding from the mouth, nose, eyes, or stomach
  • Organ failure, especially kidney and liver

Around 30-50% of those who enter the toxic phase can die.

3. Transmission

• Mosquito bites

The primary vectors are Aedes and Haemagogus mosquitoes. The disease can be transmitted in various cycles: jungle (sylvatic), inter-human (urban), and savannah.

• Monkey reservoirs

In the jungle cycle, the virus circulates between non-human primates and mosquitoes. Humans get infected when they venture into the jungle.

4. Treatment

• Supportive care

There’s no specific antiviral treatment for yellow fever. Treatment focuses on relieving symptoms and includes hydration, pain relief, and fever reducers. Hospitalization may be necessary for severe cases.

• Medication

It’s crucial to avoid certain medications like aspirin or nonsteroidal anti-inflammatory drugs (NSAIDs) because they can increase the risk of bleeding.

5. Prevention

• Vaccination

There is an effective vaccine against yellow fever, which provides lifelong immunity for most people. It’s recommended for travelers to and residents of areas where yellow fever is endemic.

• Mosquito control

This includes reducing the number of natural water-holding containers (like pots and old tires), using insecticides, and introducing mosquito predators.

• Personal protective measures

Using insect repellent, wearing long-sleeved clothing, using bed nets, and staying in accommodations with screened or air-conditioned rooms can reduce the risk of mosquito bites.

• Travel restrictions

Some countries require proof of yellow fever vaccination upon entry, especially if travelers come from endemic areas.

Regular surveillance and rapid response to outbreaks are critical in managing yellow fever. With the combined efforts of vaccination campaigns and mosquito control, the incidence of yellow fever can be significantly reduced.

Conclusion

Zoonotic diseases, resulting from pathogens transmitted between animals and humans, highlight the interconnectedness of ecosystems and the potential global impacts on public health. From rabies to COVID-19, these diseases vary in symptoms, transmission methods, and treatments, but uniformly emphasize the need for proactive measures, surveillance, and research. Understanding and mitigating these diseases require multi-faceted approaches, combining veterinary, environmental, and human health disciplines. As human-animal interactions increase, through habitat encroachment or agriculture, enhanced international cooperation and preparedness are crucial to predict, prevent, and respond to future zoonotic outbreaks, safeguarding both public health and the world’s biodiversity.