Zoonotic Diseases

A zoonotic disease is one that is naturally transmitted between humans and animals. At least 150 diseases are known to be zoonotic, varying in severity from being a nuisance to having a fatal outcome. Diseases such as rabies are transmitted by animals showing obvious signs of illness, whereas other diseases such as toxoplasmosis or cat scratch disease (bartonellosis) can be transmitted by cats that appear healthy. Fortunately, a few simple precautions are needed to reduce the risk of transmission of zoonotic disease.

This section highlights the most important zoonotic diseases that people living in Canada can acquire from cats. The information given here is an overview only, and readers with an interest in a particular disease are encouraged to obtain additional information from their physician, their cat’s veterinarian, local public health officials, or the references listed at the end of this document.

Transmission of Zoonoses

There are several routes by which people can become infected with a zoonotic agent:

  • Many zoonotic diseases are transmitted by oral ingestion of infective material, usually feces or water, soil, or food contaminated by feces. Some zoonotic agents that are found in feces are immediately infective (e.g., Campylobacter, Giardia, Cryptosporidium, Salmonella), whereas other agents require a period of time outside the cat to become infective (e.g., Toxoplasma, Toxocara). The most effective way of preventing ingestion of fecally transmitted infectious agents is to routinely practice good hygiene, including hand washing and wearing gloves when handling feces or materials contaminated with feces.
  • Several zoonotic diseases, including ringworm and Cheyletiella infection, are transmitted by direct skin contact when grooming, petting, or sleeping with an infected animal. As hands are the usual site of contact, routine hand washing is the single best way to prevent infection by this route.
  • Some zoonotic diseases (e.g., rabies, cat scratch disease) are acquired through bites or scratches respectively, from a cat carrying the organism so avoidance of interactions or circumstances that may lead to a bite or scratch is important to prevent transmission.
  • A few zoonoses (e.g., plague) can be transmitted when a person breathes air that is contaminated with a virus, bacteria, or fungus that has been shed by an infected animal. This is believed to be an uncommon route of disease transmission from cats to people in Canada.

How Great is the Risk?

The American Association of Feline Practitioners Feline Zoonoses Guidelines conclude that humans are unlikely to acquire infectious diseases from healthy adult, parasite-free cats. Many zoonotic agents, including Cryptosporidium and Salmonella, are more likely to be transmitted between people than to be acquired from an animal companion. People who are at increased risk of developing serious illness when exposed to zoonotic organisms should take extra precautions to minimize their risk of infection. Examples of people who may be at increased risk include:

  • Very young children or very elderly people
  • Those who are immunocompromised; for example, people infected with human immunodeficiency virus, people undergoing cancer chemotherapy or radiation treatment, and people taking immunosuppressive medications such as prednisone or cyclosporine
  • Those with a serious systemic disease such as diabetes mellitus or chronic kidney disease
  • Pregnant women

According to the Centers for Disease Control Guidelines for Prevention and Treatment of Opportunistic Infections in HIV-infected Adults and Adolescents (see Resources), immunocompromised individuals obtaining a new pet should adopt only flea-free cats over 6 months of age with no history of diarrhea or illness. If diarrhea occurs, veterinary care should be sought, and a fecal sample from the affected pet should be examined for Cryptosporidium, Salmonella, Giardia, and Campylobacter. Effective, regular flea prevention and control will reduce or eliminate the risk of bartonellosis in both indoor and indoor/outdoor cats.

General Guidelines for Preventing Transmission of Zoonotic Diseases

  • All cats should be regularly examined by a veterinarian, who can provide appropriate vaccinations and control measures for external and internal parasites.
  • Indoor cats and those with only supervised outdoor access have a lower risk of acquiring some zoonotic diseases than free-ranging cats because they have limited access to other cats and wildlife.
  • Feed cats only cooked or commercially prepared foods. Discourage predation of mice, birds, and other wildlife by restricting outdoor access or through the use of bells, bird-safe cat collars (see Resources), and other methods to reduce hunting success.
  • Remove fecal material from litter boxes daily and clean boxes regularly. Wear gloves when handling cat feces or litter and wash hands immediately.
  • Persons at increased risk of zoonotic diseases should wash their hands after gardening, food preparation, handling cats, as well as before food preparation and eating. If soap and water are not immediately available, alcohol-based gels or hand wipes can be used as a temporary measure. Contact with animal excrement should be avoided.
  • Avoid handling animals that are known to be carrying zoonotic agents (e.g., a cat with ringworm). Cats with diarrhea or other obvious signs of illness should receive veterinary attention and should not be handled by immunocompromised people, the elderly, or very young children. If it is necessary to handle a cat that is known or suspected to be carrying a potentially zoonotic disease, wear gloves and wash hands immediately afterwards.
  • People whose work or lifestyle puts them at risk of exposure to rabies should be vaccinated against this disease.

TOXOPLASMOSIS is of special concern to pregnant women, because women who are infected with Toxoplasma gondii for the first time during pregnancy can transmit the infection to the fetus. Depending upon the age of the fetus when the mother is exposed, infection may result in abortion or still birth, or cause brain or ophthalmic disease in the fetus. Although it is likely that exposure to tissue cysts from handling or eating undercooked meat is the most common route whereby pregnant women are exposed to this disease, it is also possible to acquire toxoplasmosis from contact with sporulated oocysts in materials contaminated with cat feces such as soil, water, or cat litter. Contact with cat feces less than 24 hours old is very unlikely to transmit toxoplasmosis as it takes 24 hours or more for the organism to become infective after shedding. For this reason, litter boxes should be scooped at least twice daily. However, pregnant women and immunocompromised people are encouraged to avoid all contact with cat feces and to wear gloves when handling material (including soil) that may be contaminated with cat feces. For women who have been previously exposed to toxoplasmosis, protective immunity likely will have developed prior to pregnancy.

Toxoplasma oocysts are not found on a cat’s hair coat, and there appears to be little or no risk of infection from handling or petting a cat. Since cats acquire toxoplasmosis by eating prey (such as mice) or undercooked meat, cats eating only commercial cat foods are very unlikely to be infected with Toxoplasma.

BARTONELLOSIS (cat scratch disease) is believed to be the most common direct zoonosis that can be transmitted from cats to people. Cats become infected with Bartonella primarily through fleas carrying the organism, and the disease appears to be more prevalent in areas with a warm and moist climate and therefore high levels of flea infestation. As the name implies, cat scratch disease is transmitted by scratches from cats with flea dirt on their nails. People become infected when the organism in the flea dirt is inoculated into their skin through a scratch. As play behaviour may involve scratching, kittens may provide a greater risk. In immunocompetent people, Bartonella infection is usually mild and self-limiting although symptoms may last for months in some patients. In immunocompromised people, bartonellosis may be a life-threatening infection.

Serologic testing of cats for Bartonella infection is not useful, nor is antibiotic treatment of healthy cats. Adult cats with no history of flea infestation are considered unlikely to transmit bartonellosis. Therefore, the main way to prevent transmission of Bartonella infection is through prevention of flea infestations.


Campylobacter jejuni

Subclinical, or mild gastroenteritis

Subclinical or gastroenteritis, myalgia, Guillain-Barre syndrome, arthralgia

Oral-fecal (ingestion of fecal material or contaminated food)
Cats: Avoid predation or feeding raw meat
People: Wash hands, avoid contact with animal feces

Salmonella species
Subclinical, or gastroenteritis (“songbird fever”), occasionally abortion or neonatal death. Symptomatic carriers may shed Salmonella

Subclinical, or gastroenteritis and fever

Ingestion of fecal material or contaminated food

Cats: Avoid predation or feeding raw poultry
People: Wash hands, avoid contact with animal feces and turtles

Cryptosporidium felis

Subclinical or small bowel diarrhea; some cats may show weight loss and anorexia

Gastroenteritis (especially children); may be fatal in people with compromised immune systems

Ingestion of fecal material or contaminated food or water
Cats: Perform periodic fecal examinations, avoid predation and access to contaminated food or water supplies
People: Wash hands, avoid handling affected animals, boil or filter contaminated surface water
Giardia (Risk from contact with infected cats is very low as people are typically infected with different types of Giardia than cats)

Subclinical or diarrhea

Flatulence, nausea, and diarrhea

Oral-fecal (ingestion of cysts from feces, or drinking water or food contaminated with excrement)

Cats: Perform periodic fecal examinations or testing
People: Wash hands, avoid drinking contaminated water
Table 1
Disease agents that can be acquired from freshly passed cat feces


Roundworms (Toxocara cati)

Usually kittens, often subclinical; may result in failure to thrive, fever, mild gastroenteritis

Visceral larva migrans (eosinophilia, abdominal pain, nausea, fever, cough, anorexia, hepatomegaly) and ocular larva migrans (severe intraocular inflammation)

Ingestion of larvated eggs in soil or water contaminated with cat feces. Eggs passed in feces require at least 1 week to become infective
Cats: Perform fecal testingregularly, administer anthelmintics and/or preventive medication, prevent predation
People: Wash hands after handling cats or cleaning litter boxes, avoid exposure to soil or water contaminated with cat feces

Toxoplasmosis (Toxoplasma gondii)

Usually subclinical. Occasionally fever, neurologic, respiratory, ophthalmic, or liver disease. Congenital infections in kittens may be fatal

Usually subclinical or flu-like disease (fever, malaise); may be fatal or cause neurologic or ophthalmic disease in immune deficient persons; if infection occurs during pregnancy, may cause abortion, still birth, or ophthalmic or neurologic disease in fetus

Ingestion of sporulated oocysts in soil or water (oocysts become infectious 1-5 days after being passed in cat feces), or ingestion of tissue cysts in infected undercooked meat
Cats: Prevent hunting. Feed commercial diet or cooked food only
People: Avoid contact with cat feces, dispose of soiled cat litter daily, use gloves and wash hands after contact with cat feces, contaminated litter, or soil; avoid ingestion or handling of undercooked meat
Table 2
Disease agents acquired from fecal contamination of the environment (agents that require time outside the cat to become infectious)


Rabies (Lyssavirus)

Progressive and fatal neurologic disease: variable changes in behaviour including restlessness and aggression, ascending paralysis, vocalization

Progressive and fatal neurologic disease; between 2000 and 2016, 4 cases of human rabies have been reported in Canada, in 2016, an outbreak of rabies in raccoons appeared in southwestern Ontario

Animal bites or wounds contaminated with saliva from an animal with rabies
Cats: Vaccinate. Avoid contact with wildlife (raccoons, bats, skunks)
People: Protect high risk people through pre-exposure vaccination, post- exposure prophylaxis after contact with rabid animal, avoid contact with wildlife including bats and raccoons

Bartonellosis (Bartonella species)

Usually subclinical; may develop fever, lethargy, and enlarged lymph nodes; possibly associated with uveitis, neurologic disease

Cat scratch disease: Enlarged lymph nodes, malaise, fever, myalgia, fatigue, headache; occasionally conjunctivitis, arthralgia; in people with immunosuppression, may cause severe disease (bacillary peliosis, bacillary angiomatosis)

Scratches (particularly from kittens) from cats with fleas, or contact with fleas
Cats: Provide regular flea control; minimize exposure to fleas; declawing does not reduce risk of disease transmission
People: Avoid scratches particularly from kittens; promptly treat scratches from cats by washing thoroughly with soap and water

Ringworm (Microsporum canis and others)

Subclinical, or skin disease (patchy hair breakage and loss, crusts, scale)

Superficial skin disease: initially red and circular lesions, mildly pruritic; later becoming dry and scaly. Nails and scalp may also be infected; young, elderly and immunocompromised people are at greatest risk

Direct contact with spores on fur or skin of affected cats or spores shed in the environment
Isolate and treat affected cats, wash hands after handling cats, wash bedding used by affected cats, avoid skin contact and wear gloves when handling cats with known or suspect infection (particularly kittens from group housing)
Table 3
Other zoonotic agents


  • Susan Little, DVM, DABVP (Feline Practice) Bytown Cat Hospital, Ottawa, Ontario
  • Diane McKelvey, DVM, DABVP (Feline Practice) Aberdeen Veterinary Hospital, Kamloops, British Columbia
  • Elizabeth O’Brien, DVM, DABVP (Feline Practice) The Cat Clinic, Hamilton, Ontario
  • Elizabeth Ruelle, DVM, DABVP (Feline Practice) Wild Rose Cat Clinic of Calgary, Calgary, Alberta
  • Kelly St. Denis, MSC, DVM, DABVP (Feline Practice)
  • Margie Scherk, DVM, DABVP (Feline Practice) catsINK, Vancouver, British Columbia

    Please Note: Not all resources are available in both English and French.