Cat Scratch Disease

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In the United States, cat scratch disease is the most common cause of chronic lymph node enlargement at one body site in young children (figure 27.15). Despite its name, this disease can be transmitted by bites, and probably other means. Typically the infection is mild and localized, lasting from several weeks to a few months. Of the estimated 24,000 annual cases, about 2,000 require hospitalization.


In about half the cases, the disease begins within a week of a scratch or bite with the appearance of a pus-filled pimple at the site of injury. Painful enlargement of the lymph nodes of the region develops in 1 to 7 weeks. About one-third of the patients develop fever, and in about half that number the lymph nodes become pus-filled and soften. The disease generally disappears without treatment in 2 to 4 months. Of the remaining 10% of cases, some develop irritation of an eye with local lymph node enlargement, epileptic seizures and coma due to encephalitis, or acute or chronic fever associated with bloodstream or heart valve infection.

Causative Agent

Cat scratch disease is caused by Bartonella (formerly Rochal-imaea) henselae, a tiny (0.6 by 1.0 mm) slightly curved Gramnegative rod cultivable on laboratory media.

Figure 27.15 Individual with Cat Scratch Disease, Showing Enlarged Lymph Node

Table 27.7 Pasteurella multocida

Bite Wound Infections


Spreading redness, tenderness, swelling, discharge of pus

Incubation period

24 hours or less

Causative agent

Pasteurella multocida, a Gram-negative, facultatively anaerobic, encapsulated coccobacillus


Introduced by bite, P. multocida attaches to tissue, resists phagocytes because of its capsule; probable cell-destroying toxin. Extensive swelling, abscess formation. Opsonins develop, allow phagocytic killing, limit spread


Carried by many animals in their mouth or upper respiratory tract

Prevention and treatment

No vaccines to use in humans. Prompt wound care is preventive.Treatment with penicillin, other anti-bacterials, effective if given promptly

27.4 Bacterial Bite Wound Infections 707

Table 27.8 Cat Scratch Disease

Symptoms Pimple appears at the bite or scratch site, followed by local lymph node enlargement, fever; nodes may soften and drain pus; prolonged fever, convulsions, indicate spread to other body parts Incubation period Usually less than 1 week Causative agent Bartonella henselae, a tiny Gram-negative rod

Pathogenesis The bacteria enter with cat bite or scratch and reach lymph nodes, where the disease is usually arrested. May spread by bloodstream, cause infections of the heart, brain, or other organs. Peliosis hepatis, bacillary angiomatosis mostly in those with AIDS

Epidemiology A zoonosis of cats, spread from one to another by cat fleas, which are biological vectors and have B. henselae in their feces. Infected cats usually asymptomatic, but often bacteremic. Humans are accidental hosts. No person-to-person spread. Mainly a disease of those less than 18 years old

Prevention and Avoiding rough play. Promptly wash skin breaks, treatment apply antiseptic. Flea control in cats. Most B. henselae susceptible to antibacterial treatment


The virulence factors of B. henselae and the process by which it causes disease are not yet known. The organisms enter the body with a cat scratch or bite, are carried to the lymph nodes, and the disease is arrested by the immune system in most cases. Spread by the bloodstream, however, occurs in some individuals. Peliosis hepatis and bacillary angiomatosis are two complicating conditions seen mostly in people with AIDS. In peliosis hepatis, blood-filled cysts form in the liver. In bacillary angiomatosis, nodules composed of proliferating blood vessels develop in the skin and other parts of the body. Bartonella henselae is present in these lesions and those of typical cat scratch disease.


Cat scratch disease mainly occurs in people less than 18 years old. The disease is a zoonosis of cats, and humans are accidental hosts. Person-to-person spread does not occur. Bites and scratches represent the usual mode of transmission of B. henselae from cats to people. Asymptomatic bacteremia is common in cats, however, and transmission from cat to cat occurs by cat fleas. The fleas are biological vectors, and they discharge B. henselae in their feces. Cat fleas probably are responsible for transmission in cases where people develop the disease after they handle cats but are not scratched or bitten. The disease occurs worldwide. ■ biological vectors, p. 491

Prevention and Treatment

There are no proven preventive measures for cat scratch disease. It is prudent to avoid handling stray cats, however, especially young ones and those with fleas. Any cat-inflicted wound should be promptly cleaned with soap and water and then treated with an antiseptic. If signs of infection develop, or if the cat's immunization status against rabies is uncertain, prompt medical evaluation is indicated. Severely immunodeficient persons should avoid cats if possible and, if not, control of fleas and abstinence from rough play is advisable. Severe B. henselae infections can usually be treated with antibacterial medications such as ampi-cillin, but some strains are resistant.

The main features of cat scratch disease are presented in table 27.8.

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