Rat bite fevers (Streptobacillus moniliformis and Spirillum minus infection)

Rat bite fever is usually attributable to Streptobacillus moniliformis in the Americas, Europe, and Australasia, and to Spirillum minus in Asia. Bites are increasingly common among children with pet rats, and pet shop and laboratory workers. Both bacteria are commensals of rats, some other rodents, and their predators. After an incubation period less than 1 week, S. moniliformis causes sudden high fever, rigors, myalgia, petechial rash, and migratory reactive or septic polyarthritis with synovial effusions. Complications can include fulminant septicaemia, endocarditis, pneumonia, and metastatic abscesses. S. minus infection (sodoku) has a longer incubation period with similarly high fever but concomitant exacerbation of the bite wound, local lymphadenopathy, papular rash, and arthralgia without effusions. In both diseases, fever subsides after a few days but may relapse repeatedly over months. Prevention is by controlling peri-domestic rats and avoiding bites by pet or laboratory rodents.