Provided by the Cornell Feline Health Center, Cornell University
What is a zoonotic disease?
While most feline infectious diseases affect only cats, and most human infectious diseases affect
only humans, it is important to be aware that some of these diseases-called zoonotic diseasescan be transmitted between cats and people. You are much more likely to contract ailments from
other humans than you are from your cat. However, simple precautions, common sense, and
good hygiene, including careful handling of litter boxes and treating cats with fleas and other
parasites, can further reduce the risk of zoonotic disease.
How are zoonotic diseases transmitted?
Transmission of a zoonotic disease can potentially occur when a person comes into direct contact
with secretions or excretions-such as saliva or feces-from an infected cat. Additionally, a disease
may be contracted through contact with water or food that has been contaminated by an infected
cat. Many zoonotic diseases can be transmitted from fleas or ticks (called vectors) to a person or
a cat from another animal.
Who is at risk?
Most zoonotic diseases pose minimal threat; however, some humans are particularly at risk.
Those with immature or weakened immune systems, such as infants, individuals with acquired
immunodeficiency syndrome (AIDS), the elderly, and people undergoing cancer therapy, are
more susceptible to zoonotic infections than others.
What are some common zoonotic diseases?
Cat-scratch disease, also called bartonellosis, is by far the most common zoonotic disease
associated with cats. Approximately 25,000 people are diagnosed every year in the United
States. Cat-scratch disease can occur when a person is bitten or scratched by an infected cat.
Fleas may also play a role in the transmission of infection. People with cat-scratch disease
usually have swollen lymph nodes, especially around the head, neck, and upper limbs. They may
also experience fever, headache, sore muscles and joints, fatigue, and poor appetite. Healthy
adults generally recover with no lasting effects, but it may take several months for the disease to
go away completely. People with compromised immune systems may suffer more severe, even
Some healthy cats are continuously or intermittently infected with cat-scratch disease bacteria,
but antibiotics do not reliably cure infection in these cats and are not currently recommended.
However, avoiding scratches and bites (for example, by not allowing children to play roughly with
cats), controlling fleas, and keeping cats indoors all reduce the risk of cat-scratch disease.
Because most cases of cat-scratch disease result from contact with kittens, immunosuppressed
people should avoid such contact.
Salmonellosis, another common bacterial disease, can cause diarrhea, fever, and stomach pain
beginning one to three days after infection. Salmonellosis usually resolves on its own. However,
some people require medical attention because the diarrhea is severe or the infection is affecting
other organs. People usually get salmonellosis by eating contaminated food, such as
undercooked chicken or eggs. However, cats and other animals-even those that appear healthycan carry and pass salmonella bacteria in their stool. Salmonella bacteria are more commonly
harbored by cats that feed on raw meat or wild birds and animals. Feline infection can be
prevented by keeping cats indoors and feeding them cooked or commercially processed food.
Human infection can be prevented by wearing gloves and washing hands thoroughly after
cleaning litter boxes (especially if used by a cat with diarrhea).
Fleas are the most common external parasite of cats. While fleas cannot thrive on humans, their
bites can cause itching and inflammation. Fleas may also serve as vectors for cat-scratch and
other zoonotic diseases. Flea-infested cats may become infected with tapeworms from fleas
ingested while grooming. Children, albeit rarely, can also become infected with tapeworms from
inadvertently ingesting fleas.
Some feline intestinal parasites, including roundworms and hookworms, can also cause disease
in people. Children are particularly at risk due to their higher likelihood of contact with
contaminated soil. Visceral larva migrans, a potentially serious disease that can affect the eyes
and other organs, results from inadvertent consumption of roundworm eggs (e.g. when soiled
fingers are placed in the mouth). Cutaneous larva migrans, an itchy skin disease, is caused by
contact with hookworm-contaminated soil. Proper hygiene, including washing hands before
meals, cleaning soil from vegetables, and reducing exposure to cat feces (e.g., by covering
children's sandboxes when not in use) can prevent infection. Anti-parasite medications for kittens
and annual fecal exams for adult cats can reduce environmental contamination and the risk of
Ringworm is not caused by a worm at all; it is a skin infection caused by a group of fungi. Infected
cats most often come from environments housing large numbers of animals. In cats, ringworm
appears as a dry, gray, scaly patch on the skin. In humans, ringworm often appears as a round,
red, itchy lesion with a ring of scale around the edge. Ringworm is transmitted by contact with an
infected animal's skin or fur, either directly or from a contaminated environment. Infected cats
continuously drop fungal spores from their skin and fur; these spores, which remain capable of
causing infection for many months, are difficult to eradicate from a household. Children are
particularly at risk of infection. To reduce environmental contamination, confine infected cats to
one room until they are free of infection; then thoroughly clean and disinfect the household.
Protozoans are single-celled organisms. The three most common protozoal diseases in cats and
humans are cryptosporidiosis, giardiasis, and toxoplasmosis. Cryptosporidiosis and giardiasis can
cause diarrhea in both cats and people, who usually become infected by a common source-for
example, contaminated water-not by each other. To prevent the spread of infection, schedule
annual fecal examinations for your cats, and medicate infected cats as directed by your
veterinarian. Other preventive measures include wearing gloves while handling fecescontaminated material, washing hands afterwards, and boiling or filtering any surface water used
Toxoplasmosis is caused by the parasitic protozoan Toxolasma gondii. People with weakened
immune systems, or infants whose mothers are infected during pregnancy, can develop severe
illness. People commonly become infected by eating undercooked or raw meat, or by
inadvertently consuming contaminated soil on unwashed or undercooked vegetables.
Unfortunately, pregnant women or immunosuppressed individuals are often mistakenly advised to
remove cats from the household to reduce the risk of toxoplasmosis. However, people are highly
unlikely to become infected from direct contact with their cats.
Cats can become infected by eating infected rodents, birds, or anything contaminated with feces
from another infected cat. An infected cat can shed the parasite in its feces for up to two weeks.
The parasite must then mature for one to five days before it becomes capable of causing
infection. However, it can persist in the environment for many months and continue to
contaminate soil, water, gardens, sandboxes, or any place where an infected cat has defecated.
Basic hygiene can prevent toxoplasmosis. Wear gloves when handling potentially contaminated
material (for example, when gardening or handling raw meat), and be sure to wash your hands
afterwards. Avoid eating undercooked meat, and thoroughly wash fruit and vegetables before
eating. Surface water should be boiled or filtered prior to drinking, and children's sandboxes
should be covered when not in use to prevent wandering cats from defecating in them. Scoop
litter boxes daily while wearing gloves, and wash your hands afterwards. Pregnant women or
immunosuppressed individuals are safest when other household members clean the litter box.
Most viruses infect only their natural host species. Human viruses, like those that cause the
common cold, infect only humans, while feline immunodeficiency virus, feline infectious peritonitis
virus, and feline leukemia virus infect only cats. However, one virus that can be passed from cats
to humans is rabies, a viral disease resulting from the bite of an infected animal. Cats are highly
susceptible to rabies, which attacks the central nervous system, causing a variety of signs.
Rabies is almost always fatal. In people, rabies infections usually occur when an infected animal
bites a person. In order to protect human health, rabies vaccination of cats is required by law in
many areas. Even if your cat is kept indoors, it is important to keep rabies vaccines current
because cats occasionally escape outdoors, and because rabid animals such as bats and
raccoons occasionally enter houses. To further reduce your risk of rabies, avoid contact with
wildlife and stray animals. See a doctor immediately if you have been bitten by an animal.
What can I do to protect my cat and myself?
Common sense and good hygiene will go a long way toward keeping you, your family, and your
cat free of zoonotic diseases. Here are a few simple precautions:
. Wash hands before eating and after handling cats.
. Schedule annual checkups and fecal exams for your cat.
. Seek veterinary care for sick cats.
. Keep rabies vaccinations current.
. Maintain appropriate flea and tick control.
. Avoid letting your cat lick your face, food utensils, or plate.
. Consider keeping cats indoors.
. Seek medical attention for cat bites.
. Feed cats cooked or commercially processed food.
. Scoop litter boxes to remove fecal material daily.
. Periodically clean litter boxes with scalding water and detergent.
. Wear gloves when gardening or handling raw meat; wash hands afterwards.
. Cover children's sandboxes when not in use.
. Wash fruits and vegetables before eating.
. Filter or boil surface water before consuming.
. Cook meat to 160°F or 80°C (medium-well-done).