Cat-scratch disease

Cat-scratch disease (also called cat-scratch fever) is an infection caused bythe Bartonella henselae bacterium, which is found in cats around theworld and is transmitted from cat to cat by fleas. It can infect people whoare scratched or (more rarely) bitten or licked by a cat that carries the bacterium.

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). 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% ofthe 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.

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).

The first sign of cat-scratch disease may be a small blister at the site of ascratch or bite 3-10 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 developson the membrane lining the inner eyelid (the palpebral conjunctiva), and isoften accompanied by inflammation (conjunctivitis) and swollen lymph nodes infront of the ear. This syndrome may be caused by rubbing one's eyes after handling the cat.

Individuals should see a doctor if a cat scratch or bite fails to heal normally or is followed by a persistent fever or other unusual symptoms such as swollen lymph nodes and long-lasting bone or joint pain. 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 nodesremain swollen and painful for more than two or three months, but there is noagreement among doctors about when and how they should be used.

Most people recover completely from a bout of cat-scratch disease, and further attacks are rare. Certain common sense precautions can be taken to guard against the disease. Scratches and bites should be washed immediately with soapand 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 withstray cats or make cats angry. Immunocompromised people should avoid owningkittens, which are more likely than adult cats to be infectious. Because cat-scratch disease is usually not a life-threatening illness and people tend toform strong emotional bonds with their cats, doctors do not recommend gettingrid of a cat suspected of carrying the disease.

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