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Column originally published Jun 19, 2001

Young Kitten Can Cause Cat Scratch Disease

Question: Recently we took in a kitten from the Humane Society. Our two-year-old son loves her. They play together all the time. As expected, he has a few scratches here and there. My sister-in-law told me that our son could pick up an infection from the kitten. Is it possible, and how can we prevent this?


Yes, it is possible to pick up an infection called “cat scratch disease” from the kitten. As the name implies, this infection usually happens after being scratched by a cat, although it can also come through a bite that punctured the skin.

Cat scratch disease is believed to be fairly common. However, most infections never progress to the full-blown “cat scratch disease,” as a result, many are not aware of its existence.

This infection is caused by the bacteria Bartonella henselae. These extremely small bacteria are very difficult to grow in routine laboratories. As a result, tissue samples sent for routine culture would produce negative result.

Domestic cats are most common animals that carry these bacteria. Kittens are often the ones identified as the source of infection. It is quite possible that at least part of the reason is the playfulness of young kittens biting and scratching their owners. The victims are often young children, again because they are more likely to play roughly with these kittens.

Once in a while, other animals like dogs have been identified as the cause of “cat scratch disease.” It is suspected that the bacteria can be spread from one animal to another through fleas. Therefore, controlling fleas may reduce the chance of infection.

After a scratch or bite, it usually takes between 5 to 12 days for infection to begin locally on the skin. This often appears as a small red swelling. The great majority of children would have no other symptom. About 1/3 can develop mild fever and feel unwell.

After another 1 to 7 weeks (average about 2 weeks), there will be swelling of the local lymph nodes in the neck, axilla, elbow, or the groin, depending on the location of the initial injury.

The area around the lymph nodes becomes red, warm, and tender. The great majority of these infected nodes would gradually resolve over several weeks to months. About 30% of the time, an abscess will develop in the infected lymph nodes, requiring surgical drainage and removal.

Diagnosis of “cat scratch disease” depends on a history of scratch or bite from a cat, as well as the typical progression of illness. The pus that is drained from these abscesses will not reveal the bacteria using routine culture technique. Examinations of the lymph nodes under microscopy often produce a fairly typical picture that can be diagnostic of this infection. In specialized laboratories, the bacteria can be identified by very sensitive staining techniques.

These infections seldom require treatment with antibiotics. Most infections probably stay at the skin level and never progress further. When the bacteria invade local lymph glands and start an infection, the normal immune system often can control and eventually eradicate the infection. If an abscess develops in the lymph gland, surgical removal of the gland usually will result in a cure.

The problem can be much more serious if the person has a weakened immune system. The bacteria can invade many essential organs. When this happens, treatment with intravenous antibiotics would be necessary.

Is there a way to prevent “cat scratch disease” at all? The only sure way is not to get a cat. In your situation, you can discourage your son playing roughly with the kitten. After 1 year of age, the cat is less likely to infect humans. If there is any scratch or bite, immediately wash the wound with soap and water. Do not allow the cat to lick any open wound. As I have mentioned earlier, good flea control can prevent your kitten from picking up the bacteria in the first place.