Introduction
Cats can transmit a variety of illnesses and diseases to humans. While the risk of disease transmission is relatively low, especially for indoor cats, it is still important for cat owners to be aware of potential zoonotic diseases that can spread from cats to humans.
This article provides an overview of some of the most common illnesses that can be transmitted from cats to humans. It covers bacterial, viral, parasitic, and fungal infections. The focus is on diseases that originate in cats and can directly spread to humans, rather than looking at illnesses that cats and humans can coincidentally acquire from a common source.
According to the Centers for Disease Control and Prevention (CDC), more than 60% of human pathogens are zoonotic and have the capability to be transmitted from animals to humans. Cats can carry a number of these zoonotic diseases. However, the transfer of disease from cats to humans requires direct or indirect contact with infected bodily fluids, so the risk is relatively low, especially if proper hygiene precautions are taken.
Toxoplasmosis
Toxoplasmosis is an infection caused by the Toxoplasma gondii parasite. This parasite is found in cat feces and spreads to humans when inadvertently ingested. According to the CDC, cats only spread the parasite for 1-3 weeks after initial infection [1]. Once infected, most healthy adults and children have no symptoms. However, those with weakened immune systems can develop more severe symptoms such as blurred vision, confusion, and lack of coordination [2].
Treatment focuses on reducing symptoms and relies on a combination of pyrimethamine (Daraprim), sulfadiazine, and Leucovorin to help stop parasite growth. Those with weakened immune systems may need to take medication for life to prevent recurrence [2].
Rabies
Rabies is a viral disease that affects the central nervous system and is almost always fatal to cats once symptoms appear. Rabies is caused by the rabies virus and is spread through the bite or scratch of an infected animal 1. In the United States, wild animals like raccoons, skunks, bats, and foxes are the most common carriers. Cats can get infected if they are bitten or scratched by a rabid animal.
The rabies virus attacks the central nervous system and causes inflammation in the brain and spinal cord. Early symptoms are subtle and include behavior changes and disorientation. As the disease progresses, infected cats may act agitated, aggressive, and experience seizures or paralysis. There is no treatment once clinical signs appear, and rabies is almost always fatal in cats.
Luckily, rabies is preventable through vaccination. Many jurisdictions require routine rabies vaccination for cats. Vaccinating cats controls the spread of rabies and protects cats, other pets, and humans from this fatal disease.
Cat Scratch Disease
Cat scratch disease is caused by a bacteria called Bartonella henselae, which cats may carry in their mouths, claws, or fur. The bacteria is transmitted to humans most commonly through a bite or scratch from an infected cat. Cat scratch disease got its name because around 80-90% of cases follow a cat scratch or bite. According to a 2016 study published by the National Center for Biotechnology Information, the estimated annual incidence of cat scratch disease is approximately 4.5 cases per 100,000 people in the US [1].
The most common symptom of cat scratch disease is swollen lymph nodes near the scratch or bite. The lymph nodes may become tender and painful. In most cases, the swollen lymph nodes go away on their own after a few weeks or months. Some people may also develop a fever, headache, exhaustion, or a rash around the scratch. While cat scratch disease usually resolves without treatment, antibiotics may be prescribed in some cases.
Campylobacter Infection
Campylobacter infection in humans is caused by the bacteria Campylobacter jejuni or Campylobacter coli. Campylobacters are commonly found in the intestines of cats and can be spread to humans through contact with cat feces.
The most common way humans get infected with Campylobacter from cats is ingesting the bacteria. This can happen through improper hand washing after changing a litter box or handling cat feces. The bacteria can also be transferred to food that is then eaten by humans. Additionally, cats grooming themselves can spread Campylobacter on their fur, which can then be transferred to humans by petting or holding the cat.
The symptoms of a Campylobacter infection include diarrhea, cramps, nausea, and fever within 2-5 days after infection. Most people have self-limited diarrhea lasting a few days to one week, but the diarrhea can last for months. While Campylobacter infections usually resolve on their own, antibiotics are sometimes prescribed for more serious cases (CDC).
Salmonella Infection
Salmonella infection in humans is caused by the Salmonella bacteria, which cats can carry in their intestinal tract and shed in their feces without showing symptoms. There are over 2,000 different serotypes of Salmonella bacteria.[1] Salmonella infection, known as salmonellosis, is spread through contact with the feces of an infected cat, usually by ingesting contaminated food or water or through improper hygiene after handling cat litter.[2] The most common symptoms of salmonellosis in humans include diarrhea, abdominal cramps, fever, nausea, and vomiting.[3] Most people recover without treatment, but the infection can be serious in infants, the elderly, and those with compromised immune systems. To prevent salmonella infection from cats, proper handwashing is key after handling cats or litter boxes. Keep cats indoors to avoid hunting prey, cook meat thoroughly, dispose of cat feces promptly, and disinfect litter boxes regularly.
[1] https://www.petmd.com/cat/general-health/salmonellosis-in-cats
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5525297/
[3] https://www.sva.se/en/what-we-do/feed-safety/general-facts-about-salmonella/salmonella-in-cats/
Ringworm
Ringworm in cats is caused by a fungal infection of the skin, fur, or claws. As the VCA Animal Hospitals notes, “Ringworm is contagious and transmission occurs by direct contact with the fungus.” The fungus can spread between cats, humans, and other animals through direct skin contact with an infected animal or person, infected surfaces, or grooming tools. In humans, ringworm often causes a ring-shaped, red, itchy rash on the skin. Cats may develop circular areas of hair loss and scaly skin. It’s important to isolate infected cats and treat them to resolve the fungal infection.
Cat Flea Typhus
Cat flea typhus is caused by Rickettsia typhi bacteria that are spread through flea bites [1]. Fleas become infected with the bacteria when they feed on infected rodents, squirrels, and opossums. The infected fleas can then transmit the bacteria to cats, which do not get sick but can carry the bacteria. When the infected fleas bite humans, the bacteria are transmitted, causing the illness known as cat flea typhus.
The most common symptoms of cat flea typhus in humans include [2]:
- Fever
- Headache
- Chills
- Muscle aches
- Rash (usually appears 5-14 days after being bitten)
While normally mild, untreated cases can occasionally lead to severe complications. Seeking prompt treatment with antibiotics is recommended.
Prevention
There are several ways to help prevent the spread of illnesses from cats to humans:
Vaccinate cats
Make sure your cat is up-to-date on all recommended vaccinations. Vaccines can help prevent diseases like rabies, feline panleukopenia, feline viral rhinotracheitis, and more. Vaccines protect both your cat’s health and reduce the risk of disease transmission. Get your cat vaccinated according to your veterinarian’s recommended schedule.
[1] https://www.vet.cornell.edu/news/20210311/how-vaccines-kitty-protect-you-too
Practice good hygiene
Wash your hands with soap and water after handling cats, cleaning the litter box, or touching any cat items. Avoid touching your face until after washing hands. Disinfect any cat scratches right away with soap and water. Keep cat claws trimmed to reduce scratch risk. Wash all wounds thoroughly.
[2] https://www.cdc.gov/healthypets/pets/cats.html
Control parasites
Use flea/tick prevention medications as directed by your vet. Clean the litter box daily and disinfect regularly. Keep cats indoors and supervise any time outside to avoid hunting small rodents or wildlife. Take unwell cats to the vet promptly for parasite testing and treatment.
Handle safely
Avoid rough play or situations which may increase scratching/biting risk. Do not allow cats to lick open wounds or near the mouth/eyes. Use caution handling stray cats or cats with unknown health histories. Consider wearing gloves when cleaning litter boxes.
[3] https://www.vet.cornell.edu/departments-centers-and-institutes/cornell-feline-health-center/health-information/feline-health-topics/zoonotic-disease-what-can-i-catch-my-cat
Conclusion
While most cat-human disease transmission is rare, there are some illnesses that cat owners should be aware of. The most concerning diseases that cats can transmit to humans are toxoplasmosis, rabies, and cat scratch disease. Toxoplasmosis can cause flu-like symptoms and brain and eye damage in people with weakened immune systems. Rabies is almost always fatal once symptoms start. Cat scratch disease causes swollen lymph nodes and fever.
To prevent disease transmission from cats, it’s important to keep cats indoors and avoid contact with stray cats. Kittens should be tested for feline leukemia virus and FIV. Cats should be kept up-to-date on vaccines, dewormed, and treated monthly with flea/tick prevention. Any bites or scratches should be washed immediately. Pregnant women and immunocompromised individuals should take extra care around cats and avoid cleaning litter boxes.
While the risks are low for most people, educating yourself on diseases cats can transmit and taking proper precautions allows you to fully enjoy the companionship of cats without worry.