Rat-bite fever

[Rihanna]

Rat-bite fever is an infection caused by either Streptobacillus moniliformis or Spirillum minus bacteria.

People usually get the infection when they are bitten by an infected rat.
Streptobacillary rat-bite fever causes joint pain.
Spirillary rat-bite fever causes swollen lymph nodes.
Both types cause a fever that comes and goes and a rash.
Doctors diagnose rat-bite fever based on the symptoms and may send a sample of blood or infected tissue to a laboratory to be cultured (streptobacillary rat-bite fever), or they may examine the sample under a microscope (spirillary rat-bite fever).
Rat-bite fever is effectively treated with antibiotics.

(See also Overview of Bacteria.)
There are two types of rat-bite fever:

Streptobacillary rat-bite fever
Spirillary rat-bite fever

Streptobacillary rat-bite fever is caused by Streptobacillus moniliformis, which lives in the mouth and throat of healthy rats, mice, and gerbils. It is a rod-shaped bacteria called a bacillus (see figure How Bacteria Shape Up). People usually get the infection when they are bitten or scratched by a wild or pet rat or mouse. Other rodents and weasels can also spread the infection. Sometimes people become infected when they drink unpasteurized milk that contains the bacteria. The infection that results from consuming the bacteria is called Haverhill fever. Streptobacillary rat-bite fever typically occurs in the United States.
Spirillary rat-bite fever (sodoku) is caused by Spirillum minus. It is a bacteria that has a spiral shape similar to spirochetes (see figure How Bacteria Shape Up). People usually get the infection when they are bitten by a rat or occasionally a mouse. Consuming Spirillum bacteria does not cause the infection. Spirillary rat-bite fever occurs primarily in Asia.