Cat Scratch Disease

Cat scratch disease (CSD), also known as cat scratch fever, is a bacterial infection in humans that is can occur when a bite or scratch from a cat breaks skin and introduces a bacteria called Bartonella henselae into the tissue. This bacteria may also be introduced to an open wound if licked by a cat that has the bacteria in their saliva.

According to the U.S. Centers for Disease Control and Prevention (CDC), “CSD is caused by a bacterium called Bartonella henselae. About 40% of cats carry B. henselae at some time in their lives, although most cats with this infection show NO signs of illness. Kittens younger than one year are more likely to have B. henselae infection and to spread the germ to people. Kittens are also more likely to scratch and bite while they play and learn how to attack prey.”

Although most cats with this bateria do not show any signs of infection, humans that are infected through exposure from their cat may notice the following symptoms develop up to two weeks after exposure:
• Swelling around the wound that may be hot and painful;
• Swelling and pain in lymph nodes near wound;
• Red, raised and sometimes pus-filled lesions;
• Headache;
• Fever;
• Fatigue;
• Loss of appetite; and
• In rare cases: muscle pain, encephalitis and eye infection.

In cats, treatment may involve a long course of antibiotics, but this is usually only the case if the cat is actually symptomatic of infection, which is rare. If you have a concern that your cat may have a bartonella infection you should seek the advice of your veterinary healthcare team. If you suspect that you may have contracted CSD from a cat, it is important to seek medical attention from your family physician. Depending on the severity of the case, you may require a treatment of antibiotics based on your individual case. According the the CDC, most cases of disease resolve on their own without antibiotic treatment.

Cats can acquire this bacteria when they are bitten by fleas that carry the bacteria, or when flea dirt (feces) enters a wound. Cats are self groomers and may inadvertently ingest the bacteria or get it stuck under their nails. Your veterinary healthcare team can offer you advice on a flea prevention treatment that can help to reduce risk. Transmission to cats is also possible if an infected cat bites or scratches another cat and passes the bacteria along. Supervising your cat and preventing their ability to interact with other cats, if it may result in bites or scratches, is ideal. This includes keeping cats indoors to prevent interaction with stray cats. When it comes to those people who may be immune compromised, it is important that their interaction with certain cats, such as those that are more rambunctious (kittens) or have a tendency to bite and scratch, are limited to prevent the spread of infection.

Kristina Cooper is a Registered Veterinary Technician (RVT) and proud member of the Ontario Association of Veterinary Technicians (OAVT). She has previously worked in both small animal practice and a municipal animal shelter. With a special interest in the relationship between animal and human health, she is currently the Provincial Manager of the OAVT Public Health Rabies Response Program and an active One Health Initiative advocate. She can be reached by email at

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