Bug Bytes Volume 1 Number 1

Cat Scratch Disease

Cat scratch disease (CSD), is the most common cause of chronic, benign adenopathy in children and young adults. Each year almost 24,000 Americans, 80% of whom are immunocompetent and younger than 21 years of age, acquire CSD. The diagnosis of CSD is clinical and requires three of the following: a scratch, bite, or primary lesion caused by a cat; a positive skin test; otherwise unexplained lymphadenopathy; or characteristic histopathology of a node biopsy. Although CSD can follow exposure to adult cats or dogs, the majority of cases are associated with exposure to kittens (scratches, bites, licks, or even a kitten's fleas). Within 3 - 5 days of exposure, the patient develops an erythematous papule or pustule at the inoculation site, and in 1 - 2 weeks develops regional adenopathy (the most common manifestation of CSD). Lymphadenopathy associated with malaise, anorexia, myalgias, and less commonly fever usually abates spontaneously in 3 to 6 weeks. Although CSD may be caused by either of two recently described members of the a-2 Subgroup of Proteobacteria, Afipia felis and Rochalimaea enselae, R. henselae is most often etiologic. Most cases of CSD do not require therapy, but in patients with severe local pain or systemic symptoms, antibiotics (ciprofloxacin, doxycycline, or erythromycin) may be of value. Because ciprofloxacin and doxycycline should be avoided in childhood, erythromycin, 500 mg BID, is the preferred treatment in children.

Three species of Rochalimaea are known to cause disease: R. quintana, R. henselae, and R. elizabethae. R. henselae also causes Bacteremia, Bacillary Angiomatosis, Bacillary Peliosis Hepatitis, and can invade virtually any organ. R. quintana (the agent of Trench Fever) can cause Bacillary Angiomatosis, and R. elizabethae can cause endocarditis. Bacillary Angiomatosis and Bacillary Peliosis Hepatitis most often occur in patients with AIDS, rarely in the immunocompetent, and should be treated promptly.

Points to remember

1. Both R. henselae and less commonly A. felis can cause Cat Scratch Disease.
2. Most patients with CSD or Bacillary Angiomatosis have cat (kitten) exposure.
3. Erythromycin is preferred treatment for infections due to Rochalimaea species.

Suggested Reading

• Adal, A. Karim et al.: Cat Scratch Disease, Bacillary Angiomatosis, and Other Infections due to Rochalimaea. NEJM. 330:1509-1515. 1994.

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