Rat bites can cause fever

Editor—Last month's article about rats included diseases transmitted by rats to humans.¹ An uncommon mode of transmission that was not included is through bites, which can cause rat bite fever. Rat bites are more likely among people living in rat infested housing or doing research with rats.

Rat bite fever is caused by either Spirillum minor (or Spirillum minus), a Gram negative spiral shaped organism (spirillar fever occurs mainly in Asia), or Streptobacillus moniliformis, a Gram negative filamentous bacillus (streptobacillary fever). These bacteria are found in the oropharyngeal flora of half of healthy wild and laboratory rats. Transmissionis only through rat bites; human to human transmission has not been documented.

After an incubation period of 7-10 days, patients develop fever, headache, and myalgia. Streptobacillary fever causes inflamed local lesion, lymphadenopathy, rash, and myalgia. Fever may be recurrent if untreated. Complications include endocarditis and pneumonia. Penicillin or doxycycline is the drug of choice. If untreated, death occurs in a tenth of cases.²

1. Welch E, Gill G. Rat race. studentBMJ 2005;13:82-3. (February.)
2. Mims C, Dockrell HM, Georing RV, Roitt I. Medical microbiology. 3rd ed. Kidlington: Elsevier, 2004.