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Cat-Scratch Disease

By Larry M. Bush, MD

Cat-scratch disease is infection caused by the bacteria Bartonella henselae and transmitted by a scratch or bite from an infected cat.

  • People with cat-scratch disease have a red bump at the site of the scratch, and some have a fever, headache, poor appetite, or swollen lymph nodes.

  • In people with a weakened immune system, the infection may spread throughout the body and, without treatment, may result in death.

  • Doctors do blood tests to check for the bacteria.

  • Usually, applying heat to the infected area and taking pain relievers are all that is needed, but if people have a weakened immune system, doctors give them antibiotics.

Most domestic cats throughout the world are infected, but most show no signs of illness.

Symptoms

At the site of a cat scratch, a red bump develops. The bump usually has a crust and sometimes contains pus. Within 2 weeks (sometimes after the scratch has healed), nearby lymph nodes swell and become tender and filled with pus. People may have a fever, headache, and poor appetite. Sometimes pus drains from the swollen lymph nodes.

Usually, people have no other symptoms, and cat-scratch disease resolves on its own. But if the immune system is weakened, as occurs in people with human immunodeficiency virus (HIV) infection or AIDS, infection can spread throughout the body and, without treatment, can be fatal.

Diagnosis

  • Blood tests

  • Sometimes lymph node biopsy

To diagnose cat-scratch disease, doctors measure antibodies to the bacteria in the blood.

Sometimes doctors take a sample of tissue from a swollen lymph node and analyze it (lymph node biopsy).

Treatment

  • Heat and pain relievers

  • Sometimes an antibiotic

For people with a healthy immune system, applying heat to the infected area and taking pain relievers are usually adequate. Sometimes doctors also give antibiotics such as azithromycin to keep the disease from spreading. However, people with a weakened immune system in whom the disease has spread need to take antibiotics. Antibiotics that may be used include ciprofloxacin, gentamicin, and doxycycline. These antibiotics need to be taken for weeks to months

People with a weakened immune system can avoid getting the infection by avoiding domestic cats.

More Information

Drugs Mentioned In This Article

  • Generic Name
    Select Brand Names
  • GENOPTIC
  • PERIOSTAT, VIBRAMYCIN
  • CILOXAN, CIPRO
  • ZITHROMAX

* This is the Consumer Version. *