OVERVIEW

What are zoonotic diseases?

Zoonotic diseases, as the name suggests, are infections caused by pathogens that can infect both animals and humans. They often originate from poultry, livestock, pets, or wild animals.

These diseases can spread through various routes, including respiratory transmission, digestive tract transmission, blood/body fluids, and close contact.

Zoonotic diseases are a highly significant category of infectious diseases, encompassing over a hundred specific illnesses depending on the pathogen. Each disease has its own symptoms, treatment options, and outcomes. Common examples include rabies, influenza, and tuberculosis.

What are some examples of zoonotic diseases?

Based on the type of pathogen, zoonotic diseases can be broadly classified into:

• Viral zoonoses: Rabies, HIV/AIDS, influenza, SARS, prion diseases, hepatitis E, Ebola hemorrhagic fever, etc.
• Bacterial zoonoses: Plague, anthrax, tuberculosis, brucellosis, streptococcal infections, salmonellosis, tularemia, etc.
• Parasitic zoonoses: Toxoplasmosis, schistosomiasis, taeniasis, cryptosporidiosis, babesiosis, giardiasis, etc.
• Fungal zoonoses: Sporotrichosis, Microsporum canis infections, etc.
• Others: Leptospirosis, Q fever, Lyme disease, ehrlichiosis, etc.

Are zoonotic diseases common?

As evident from the variety of zoonotic diseases mentioned above, they are far more common than many realize. Approximately 75% of human infectious diseases are zoonotic, including:

• Seasonal outbreaks like influenza;
• Diseases such as tuberculosis, which were once well-controlled but are now seeing a resurgence;
• Conditions like toxoplasmosis and brucellosis, which have notable prevalence among pet owners and livestock handlers.

What are the differences between zoonotic diseases, animal-borne diseases, and natural focal diseases?

These three terms may seem similar, but their definitions overlap in certain ways. While we’ve already explained zoonotic diseases, the latter two terms mean:

• Animal-borne diseases: Infections transmitted from animals to humans, where animals serve as the source of transmission.
• Natural focal diseases: Diseases that persist in specific natural environments, involving pathogens, vectors, and hosts within a particular ecological system.
  In other words, these diseases can exist or spread even without human involvement. When humans enter these areas, they may become infected. Such regions are called natural foci, and the diseases are termed natural focal diseases. Examples include plague and tick-borne encephalitis.

SYMPTOMS

What symptoms do zoonotic diseases generally cause?

See details for each specific disease.

What are the hazards of zoonotic diseases?

The dangers of zoonotic diseases can be discussed in terms of their impact on affected individuals and families, as well as broader societal and economic consequences.

From the list of zoonotic diseases, we can easily recognize many "notorious" illnesses, including:

• Rabies, Ebola hemorrhagic fever, and other diseases with no effective treatment and extremely high mortality rates;
• Plague, anthrax, and other highly contagious diseases that can cause large-scale outbreaks if not properly controlled;
• Tuberculosis, AIDS, and other diseases for which some treatments exist but still have poor prognoses and are prone to complications due to weakened immunity.

Even the recent global outbreak of COVID-19 has caused immeasurable losses, affecting patients and their families, the world economy, and even political landscapes.

CAUSES

Which animals commonly carry zoonotic diseases?

Zoonotic diseases are commonly found in:

• Livestock, including cattle, sheep, pigs, horses, etc.;
• Poultry, including chickens, ducks, pigeons, etc.;
• Household pets, including cats, dogs, parrots, etc.;
• And some wild animals, such as bats, pangolins, marmots, etc.

What zoonotic diseases can be caused by pet dogs?

Pet dogs may transmit rabies, pasteurellosis, canine brucellosis, salmonella infection, campylobacter infection, cryptosporidiosis, giardiasis, etc.

Additionally, many parasitic diseases can be transmitted from dogs to humans through feces, including toxocariasis, cutaneous larva migrans, echinococcosis, and hookworm infection.

What zoonotic diseases can be caused by pet cats?

Cats can transmit many zoonotic diseases similar to those caused by dogs, such as rabies, cutaneous larva migrans, Yersinia pestis, tularemia, and murine typhus. They can also spread feline-specific zoonoses, including cat scratch disease, toxoplasmosis, and Sporothrix schenckii infection.

Which groups are most susceptible to zoonotic diseases?

Most zoonotic diseases are most common among people who have close contact with animals due to work or other reasons. Examples include poultry and livestock farmers, workers involved in animal quarantine, slaughtering, or processing, those in close contact with pets, and individuals who illegally hunt, trade, or consume wild animals.

Elderly individuals, pregnant women, children, and those with immunocompromising conditions are at higher risk of infection under the same circumstances.

For highly contagious zoonotic diseases like SARS and influenza, the general population is susceptible. During outbreaks, transmission can occur through respiratory droplets or close contact with infected individuals, even without direct animal exposure.

How are zoonotic diseases transmitted?

Transmission routes vary depending on the specific pathogen and disease. For example, influenza and SARS spread through droplets, while hepatitis E and salmonellosis are transmitted via the fecal-oral route. HIV spreads through blood/body fluids and sexual contact.

DIAGNOSIS

What conditions must be met to diagnose zoonotic diseases?

Diagnosing zoonotic diseases is usually not easy.

Because many diseases have atypical symptoms, diverse clinical manifestations, and relatively concealed modes of infection, they are easily confused with other diseases. Unless there is a very clear history of high-risk animal exposure + typical symptom presentation, doctors usually do not first consider zoonotic diseases.

To diagnose a zoonotic disease, corresponding epidemiological history, typical symptoms and signs, auxiliary examinations, and etiological diagnostic evidence are required.

TREATMENT

Which department should I visit for zoonotic diseases?

Zoonotic diseases encompass hundreds of specific illnesses with varying symptoms, so patients are often initially referred to specialized departments based on their presenting symptoms, such as dermatology, gastroenterology, or respiratory medicine. However, once diagnosed, it is recommended to seek treatment in the infectious diseases department.

Which zoonotic diseases are relatively easier to treat?

There is no simple metric to determine how easily a zoonotic disease can be treated.

Theoretically, diseases with clearly identified pathogens, typical symptoms, and well-established diagnostic and treatment protocols are relatively easier to manage, such as brucellosis, salmonella infection, and hepatitis E.

However, some "easily treatable" diseases may develop complications or severe cases, such as influenza, leading to serious consequences.

Which zoonotic diseases are more difficult to treat?

• One category includes diseases with known pathogens but no effective treatment, such as rabies, Ebola hemorrhagic fever, and AIDS, which still have extremely high mortality rates.
• Another category consists of diseases that, while not severe or life-threatening, cannot be completely cured or are prone to recurrence, such as tuberculosis and cryptosporidiosis.
• Additionally, diseases that are highly contagious and prone to outbreaks are challenging to treat, posing not only a challenge for individual patients but also a global public health threat.

DIET & LIFESTYLE

Do patients with zoonotic diseases need to be isolated?

The vast majority of zoonotic diseases require isolation treatment, with measures varying depending on the disease's infectivity and severity. For example:

• Influenza can be managed with self-isolation at home;
• Highly contagious diseases like SARS, especially those transmitted via respiratory droplets or aerosols, require isolation treatment in negative-pressure hospital rooms;
• Well-controlled conditions such as HIV, inactive tuberculosis, or fungal skin infections may not require isolation.

Can zoonotic diseases be contracted from visiting zoos?

Visiting a zoo under normal circumstances does not lead to zoonotic diseases. Avoid direct contact with animals, wash hands promptly after any interaction, and refrain from touching mucous membranes (e.g., eyes, nose) with unwashed hands.

However, immunocompromised individuals—such as those with HIV, post-organ or hematopoietic stem cell transplants, or those on long-term immunosuppressants or corticosteroids—are advised against visiting zoos.

PREVENTION

How to Prevent Zoonotic Diseases?

Preventive measures for zoonotic diseases correspond directly to their risk factors:

• For individuals engaged in livestock and poultry breeding, slaughtering, processing, or quarantine work, strict adherence to operational protocols, standard protective measures, regular animal health checkups, and early detection, treatment, and isolation of infected animals are essential;
• Pet owners should vaccinate their pets as scheduled, conduct regular health checkups, and avoid overly intimate contact with pets;
• Avoid consuming meat of unknown origin or undercooked meat;
• Severely crack down on the hunting, trafficking, and consumption of wild animals;
• Report confirmed cases promptly, implement isolation and treatment, and prevent the spread of outbreaks.

How to Prevent Zoonotic Diseases If You Have a Pet Dog?

The risk of disease transmission from normal dog care and interaction is very low and can be further reduced by the following measures:

• Schedule regular health checkups and rabies vaccinations for your dog; seek immediate veterinary care if symptoms like diarrhea occur;
• Before adopting a stray dog, ensure a thorough veterinary examination and safety assessment;
• Provide safe food and drinking water for your dog; avoid feeding raw meat or eggs and prevent dogs from eating garbage, feces, or drinking from puddles or toilets;
• Supervise interactions with other dogs or animals of unknown health status outdoors; seek prompt medical attention for any bites or scratches during play;
• Wear gloves and a mask when handling dog waste and wash hands immediately afterward;
• Avoid excessive intimacy, such as kissing or allowing licking, especially if you have broken skin or mucous membranes;
• If scratched or bitten, clean the wound immediately and consult a doctor about rabies vaccination.

How to Prevent Zoonotic Diseases If You Have a Pet Cat?

The risk of disease transmission from normal cat care and interaction is very low. Preventive measures are similar to those for pet dogs:

• Schedule regular health checkups and rabies vaccinations for your cat; seek prompt veterinary care for abnormal symptoms (especially diarrhea or skin conditions);
• Before adopting a stray cat, ensure a thorough veterinary examination and safety assessment;
• Provide safe food and drinking water; avoid feeding raw meat or eggs and prevent cats from drinking from puddles or toilets;
• Regularly trim your cat's claws to reduce the risk of scratches;
• Wear gloves and a mask when handling cat waste and wash hands immediately afterward;
• Avoid excessive intimacy, such as kissing or allowing licking, especially if you have broken skin or mucous membranes;
• If scratched or bitten, get a rabies vaccination immediately;
• Pregnant women or those planning pregnancy should avoid keeping pet cats due to the risk of toxoplasmosis, which may cause fetal malformations, premature birth, or miscarriage;
• Young cats (under 1 year old) pose a higher disease risk than older cats. If there are elderly, children, or immunocompromised family members but a strong desire to keep a cat, consider adopting a fully vaccinated and health-checked adult cat;
• Note: Individuals with immunosuppressive conditions (e.g., HIV/AIDS, post-organ or stem cell transplant, long-term immunosuppressant or corticosteroid use) should avoid keeping cats or other animals.

How to Prevent Zoonotic Diseases If You Have a Pet Parrot?

• Ensure the parrot comes from a safe, reliable source and has undergone proper quarantine procedures;
• Avoid overly close contact with the parrot;
• Wear a mask and gloves when cleaning the cage or handling waste, and wash hands immediately afterward;
• Seek veterinary care promptly if the parrot shows abnormal behavior;
• Consider vaccinations for psittacosis and influenza.