Cat scratch disease

Cat scratch disease is a disease of people carried by cats. Infected cats usually do not show any sign of illness but the disease can be passed to humans via a bite or scratch from the cat.

Cat scratch disease (CSD), also known as Bartonellosis, is caused by a bacteria carried in the blood of cats. CSD is a zoonotic disease, ie it is an infectious disease that can be transmitted from cats to other animals and to people.

The disease is well recognized in North America but is also seen in Europe and increasingly in the UK.

The disease is spread from cat to cat via the cat flea and then can be transmitted to humans via a bite or scratch. While fleas do not directly pass the infection to humans, controlling fleas in cats may decrease the risk of infection to humans; primarily as cats are less likely to become infected if fleas are not present.

Ticks are also a major transmitter of the disease. Ticks also carry other infectious diseases such as Lyme disease. People can be infected with both infections at the same time and, since symptoms of the two conditions may be similar, CSD may be missed when testing for Lyme disease.

Infected cats carry the bacteria in their blood. It appears that the disease can only be spread via infected blood but cats saliva can be contaminated with blood so that the disease can be transmitted by bites or licking. Cats may also contaminate their nails with infection whilst grooming and the infected blood may enter the human body through a cat scratch. Cats with fleas are more likely to scratch themselves than so in infected cats scratching increases the risk of the cat contaminating its nails with infected blood and passing the disease onto humans.

Kittens are more likely to carry the bacteria in their blood, and are therefore more likely to transmit the disease than are adult cats.

Cats usually do not show any symptoms but if your cat is sick with clinical signs suggestive of infection your vet can take a blood sample and send the sample to a laboratory for testing to confirm infection. There is no benefit in screening healthy cats for infection.

The bacteria can be relatively easily treated with antibiotics. Your veterinarian may prescribe antibiotics to treat cats when Bartonella infection has been found in their blood.

Regular flea control is the best way to avoid Bartonella infection in your cat. Stray cats under a year of age are most likely to be infected.

People may not realize that they have been infected with CSD. The first sign of infection may be a small blister or lump at the site of a wound. In most cases the most severe signs are swelling of the glands (lymph nodes) near the site of the scratch or bite 2-3 weeks after infection. Occasionally, an infected lymph node may form a tunnel through the skin and pus will drain out. Cat scratch disease is a common cause of chronic lymph node swelling in children.

Other symptoms that may be seen in some people include:

• Fever
• Tiredness, lethargy
• Overall generalized discomfort
• Headache

Generally, cat scratch disease is not serious and medical treatment is not usually needed. In AIDS patients and in other people who have suppressed immune systems, cat scratch disease is more serious, and treatment with antibiotics is recommended. For some reason most infections occur in the fall and winter.

Since the disease can only be spread through infected cat blood you should avoid contamination of wounds with cat saliva or blood.

• Avoid “rough play” (or any activity that may result in biting or scratching) with cats, especially kittens. If you are bitten or scratched wash the affected area thoroughly.
• Do not allow cats to lick your skin (especially if you have any open wounds).
• Control fleas on your cat.
• If you develop an infection (with pus and pronounced swelling) where you were scratched or bitten by a cat; or if you develop any symptoms, including fever, headache, swollen lymph nodes, and fatigue, contact your doctor for advice.
• In some countries declawing has been proposed as a potential way to reduce the risk of transmission of infection; however there is no evidence to support this theory. Furthermore declawing is not a recommended procedure for cats as it is associated with negative long-term health and behavioral consequences. 

More recommendations can be found on the Center for Disease Control website at www.cdc.gov/bartonella.