Rat-bite fever

Alternative names:

Haverhill fever; sodoku; streptobacillary fever; streptobacilliary fever

Definition:

An infectious disease transmitted by the bite of a rat or, on occasion, exposure to a substance contaminated by rats.

Causes, incidence, and risk factors:

Rat-bite fever is caused by two separate organisms, Streptobacillus moniliformis and spirillum minus, which is introduced into the body by the bite of a rat (may occur in other wild animals as well). The disease spectrum varies depending on what organism predominates. The incubation period is one week or less and begins with fever and chills, headache, muscle aches, weakness and sore throat. A rash appears on the 2nd or 3rd day, often on the hands or feet. An arthritis develops in approximately 50% of infected people.

Symptoms subside within 1 week but irregular recurrences of the same symptoms will occur over the next several months. The illness ultimately is self-limiting and symptoms disappear. An occasional untreated case can be fatal.

A slightly different presentation of this illness is cause by Spirillum minor, which is also carried by rats and other rodents. It has a longer incubation period and the site of the bite develops into an open crusted sore. (This is sodoku).