“Rat-bite fever” is a general term to describe two relatively rare bacterial infections: Streptobacillus moniliformis, also known as Haverhill fever, and Spirillum minor, also known as Sodoku.

Image/National Park Service
Image/National Park Service

Both bacteria are normal or commensal organisms found in rats and to a lesser extent other rodents and mammals.

These infections are found worldwide, but seen most commonly in Asia and Africa.

The bacteria are found in the oral and nasal secretions of the infected rat. It can also be found in the rat’s urine.

Transmission to people is most frequently the result of a rat bite, however direct contact with the rats is not always necessary. People who work or live in rat infested buildings are also at risk and it has been transmitted through contaminated water and milk.

After about a week after being exposed, there is an abrupt onset of chills, fever, headache and muscle pains.

With S. moniliformis, a rash on the extremities appears after a few days. Arthritic symptoms may also be present.

On the other hand with S. minor, an ulcerated lesion at the bite site is typical and symptoms of arthritis are rare.

Untreated cases can be fatal in up to 10% of cases. Endocarditis, pericarditis and abscesses of the brain are complications of untreated rat-bite fever.

Diagnosis of S. moniliformis can be confirmed through culture of primary lesion, blood, lymph node or joint fluid on specialized media. S. minor has not been cultured on artificial media and animal inoculation is required.

Penicillin or tetracycline can be used to treat the infection.

Originally published on examiner.com on Nov. 29, 2009

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