Our son was just diagnosed with cat-scratch fever after he had a biopsy of one lymph node in his armpit. Do we need to get the cat tested? How can we prevent this from happening again?

O.

Cat-scratch disease is a very common illness, especially in children, but the cause was only recently discovered. Most cases are due to the bacterium Bartonella henselae. This bacterium is very common in cats, having been found in the blood of almost a third of kittens tested. The microbe doesn't cause disease or other problems for the cats.

People who get cat-scratch disease usually have a harmless illness that goes away without treatment. Most cases arise about two weeks after a person has been scratched by a cat. In some cases, some other type of contact with a cat has occurred. In rare cases, a person develops the disease without any known contact with a cat.

Untreated, the infection generally slowly resolves with no lasting effects. However, the lymph node may stay swollen for several months and occasionally more than a year.

It is not easy to make a definitive diagnosis of cat-scratch disease. Surgically removing the node for biopsy can help. Growing the organism is very difficult and is only accomplished in specialized laboratories. Since the disease is usually harmless, such tests are not regularly performed.

Few research studies have looked at the effectiveness of antibiotic therapy in this disease, but it appears that medicines may help. Azithromycin (trade name Zithromax) and ciprofloxacin (trade name Cipro) are the antibiotics most commonly used, though ciprofloxacin is not prescribed for children.

As to your cat, there is really no reason to get the animal tested. I am sure it has the bacterium. To prevent this from happening again, you need to avoid getting scratched. Although there are no data to prove that cleaning a scratch can prevent cat-scratch disease, I recommend cleaning the wound as soon as the cat scratches anyone.