cat-scratch disease

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Related to cat-scratch disease: brucellosis, toxoplasmosis, Bartonella henselae

Cat-Scratch Disease



Cat-scratch disease is an uncommon infection that typically results from a cat's scratch or bite. Most sufferers experience only moderate discomfort and find that their symptoms clear up without any lasting harm after a few weeks or months. Professional medical treatment is rarely needed.


Cat-scratch disease (also called cat-scratch fever) is caused by the Bartonella henselae bacterium, which is found in cats around the world and is transmitted from cat to cat by fleas. Researchers have discovered that large numbers of North American cats carry antibodies for the disease (meaning that the cats have been infected at some point in their lives). Some parts of North America have much higher rates of cat infection than others, however. Bartonella henselae is uncommon or absent in cold climates, which fleas have difficulty tolerating, but prevalent in warm, humid places such as Memphis, Tennessee, where antibodies were found in 71% of the cats tested. The bacterium, which remains in a cat's bloodstream for several months after infection, seems to be harmless to most cats, and normally an infected cat will not display any symptoms. Kittens (cats less than one year old) are more likely than adult cats to be carrying the infection.
Bartonella henselae can infect people who are scratched or (more rarely) bitten or licked by a cat. It cannot be passed from person to person. Although cats are popular pets found in about 30% of American households, human infection appears to be rare. One study estimated that for every 100,000 Americans there are only 2.5 cases of cat-scratch disease each year (2.5/100,000). It is also unusual for more than one family member to become ill; a Florida investigation discovered multiple cases in only 3.5% of the families studied. Children and teenagers appear to be the most likely victims of catscratch disease, although the possibility exists that the disease may be more common among adults than previously thought.

Causes and symptoms

The first sign of cat-scratch disease may be a small blister at the site of a scratch or bite three to 10 days after injury. The blister (which sometimes contains pus) often looks like an insect bite and is usually found on the hands, arms, or head. Within two weeks of the blister's appearance, lymph nodes near the site of injury become swollen. Often the infected person develops a fever or experiences fatigue or headaches. The symptoms usually disappear within a month, although the lymph nodes may remain swollen for several months. Hepatitis, pneumonia, and other dangerous complications can arise, but the likelihood of cat-scratch disease posing a serious threat to health is very small. AIDS patients and other immunocompromised people face the greatest risk of dangerous complications.
Occasionally, the symptoms of cat-scratch disease take the form of what is called Parinaud's oculoglandular syndrome. In such cases, a small sore develops on the palpebral conjunctiva (the membrane lining the inner eyelid), and is often accompanied by conjunctivitis (inflammation of the membrane) and swollen lymph nodes in front of the ear. Researchers suspect that the first step in the development of Parinaud's oculoglandular syndrome occurs when Bartonella henselae bacteria pass from a cat's saliva to its fur during grooming. Rubbing one's eyes after handling the cat then transmits the bacteria to the conjunctiva.


A family doctor should be called whenever a cat scratch or bite fails to heal normally or is followed by a persistent fever or other unusual symptoms such as long-lasting bone or joint pain. The appearance of painful and swollen lymph nodes is another reason for consulting a doctor. When cat-scratch disease is suspected, the doctor will ask about a history of exposure to cats and look for evidence of a cat scratch or bite and swollen lymph nodes. A blood test for Bartonella henselae may be ordered to confirm the doctor's diagnosis.


For otherwise healthy people, rest and over-the-counter medications for reducing fever and discomfort (such as acetaminophen) while waiting for the disease to run its course are usually all that is necessary. Antibiotics are prescribed in some cases, particularly when complications occur or the lymph nodes remain swollen and painful for more than two or three months, but there is no agreement among doctors about when and how they should be used. If a lymph node becomes very swollen and painful, the family doctor may decide to drain it.


Most people recover completely from a bout of cat-scratch disease. Further attacks are rare.


Certain common-sense precautions can be taken to guard against the disease. Scratches and bites should be washed immediately with soap and water, and it is never a good idea to rub one's eyes after handling a cat without first washing one's hands. Children should be told not to play with stray cats or make cats angry. Immunocompromised people should avoid owning kittens, which are more likely than adult cats to be infectious. Because cat-scratch disease is usually not a life-threatening illness and people tend to form strong emotional bonds with their cats, doctors do not recommend getting rid of a cat suspected of carrying the disease.



Smith, David L. "Cat-Scratch Disease and Related Clinical Syndromes." American Family Physician April 1997: 1783.

Key terms

Acetaminophen — A drug for relieving pain and fever.
AIDS — Acquired immunodeficiency syndrome. A disease that attacks the immune system.
Antibiotics — A category of manufactured substances used to combat infection.
Antibodies — Special substances created by the body to combat infection.
Bacterium — A tiny organism. Some bacteria cause disease.
Hepatitis — A disease that inflames the liver.
Immune system — A body system that combats disease.
Immunocompromised — Having a damaged immune system.
Lymph nodes — Small, kidney-shaped organs that filter a fluid called lymph.
Pneumonia — A disease that inflames the lungs.
Pus — A thick yellowish or greenish fluid.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.

cat-scratch disease (fever)

a benign, subacute, regional lymphadenitis resulting from a scratch or bite of a cat or a scratch from a surface contaminated by a cat. The causative agent is the bacterium Bartonella henselae. Cats thought to be associated with human infection show no signs of illness, and probably act only as vectors of the disease, conveying the causative agent on claws or teeth.

In half the cases, after several days there is a persistent sore at the site of the scratch, and fever and other symptoms of infection may develop. There is also swelling of the lymph nodes draining the infected part. In milder cases, the symptoms soon disappear, with no aftereffects. Sometimes the attack is more serious and the glands may require surgical incision and drainage. Occasionally meningoencephalitis is a serious complication. The disease is generally mild and lasts for about 2 weeks. In rare cases, it may persist for a period of up to 2 years.

No specific remedy exists for cat-scratch disease, although certain antibiotics appear to shorten its course. The main treatment consists simply of keeping the patient as comfortable as possible. The disease can, however, usually be prevented by avoiding cat scratches or bites or by thoroughly washing and disinfecting any wound that does occur.

note: Not to be confused with cat-bite fever.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
References in periodicals archive ?
Carithers, "Cat-scratch disease associated with an osteolytic lesion," Archives of Pediatrics and Adolescent Medicine, vol.
Generally, cat-scratch disease is a self-limiting disease, with good visual prognosis, but treatment may hasten recovery [20, 31].
Fragulidis, "Seronegative cat-scratch disease diagnosed by PCR detection of Bartonella henselae DNA in lymph node samples," Brazilian Journal of Infectious Diseases, vol.
Cat-scratch disease is transmitted to humans through scratches, licks, or bites from kittens, less often from older cats, and sometimes from dogs.
Cat-scratch disease bacilli are focal and do not readily stain with a Gram's stain.
Cat-scratch disease occurs when the bacteria on an infected cat's claws enter the human bloodstream.
Neurologic manifestations of cat-scratch disease. Report of a case and review of the literature.
Retinal and choroidal manifestations of cat-scratch disease. Ophthalmology.
-- Consider the possibility of cat-scratch disease encephalopathy in anyone with new-onset seizures-especially status epilepticus--and no alternative diagnosis, Dr.
Findings on histologic examination suggested cat-scratch disease, but the patient had no history of contact with cats.
Cat-scratch disease due to Bartonella henselae is a well-known cause of regional lymphadenitis in children and adolescents.