Cat-Scratch Disease (CSD)

Cat-scratch disease (CSD) is a bacterial zoonotic (transmitted from animals to humans) disease spread by cats. It is caused by the bacterium Bartonella henselae.

About 40% of cats carry this bacteria at some time in their lives, although most cats with this infection show NO signs of illness. Kittens younger than one year are more likely to have Bartonella henselae infection and to spread the germ to people.

The disease spreads when an infected cat licks a person’s open wound, or bites or scratches a person hard enough to break the surface of the skin.

Child kissing a cat on the nose

 

About three to 14 days after the skin is broken, a mild infection can occur at the site of the scratch or bite.

A blister or papule may be appear at the site of the bite, scratch, or lick from a cat, followed several days later by swelling of the lymph nodes.

Low-grade fever and discomfort at the lymph node site are common. Affected lymph nodes may become filled with pus and spontaneously erupt.

Although CSD will usually resolve without treatment, more serious cases can occur weeks or months after the initial onset. These symptoms may include granulomatous lesions of the liver or spleen, brain disease, (which may cause seizures, coma, and combative behavior), inflammation of the neural retina and optic nerve, endocarditis, and inflammation of bone or bone marrow.

In people with impaired immune systems, such as HIV-positive patients and people on immune suppressive drug therapy, signs may be significantly modified and may persist indefinitely depending on the extent of immune suppression. Persistent bacteria in the bloodstream and significant recurrent fever are likely.

Untreated Bartonella infections in immune impaired persons may be life-threatening.

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Last Revised: September 14, 2021