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Rat-Bite FeverRats

Rat-bite fever is a bacterial infection caused by one of two bacteria: Streptobacillus moniliformis and Spirillum minus.  Healthy rats can carry these bacteria in their nose and mouth and are the reservoir of infection in people.  Most people become infected after a rat bite, although outbreaks have occurred when people ingested milk or water contaminated with rat feces.

These two bacteria cause a similar syndrome of fever, headache, chills and muscle pain with frequent relapses.  Symptoms of infection with S. moniliformis usually occur within two to 14 days after a rat bite and can sometimes progress to arthritis in multiple joints.  S. minus has a longer incubation period of one to four weeks and is usually characterized by reddish or purple plaques on the skin as well as the symptoms mentioned above.  Treatment is with appropriate antibiotics, and mortality can reach 10 percent in untreated individuals.

Animals associated with rat-bite fever include:

  • Rats:  Rats carry S. monoliformis and S. minus in their nose and mouth and serve as a source of infection to people.

Steps to reduce your risk of rat-bite fever:

  • Avoid contact with rodents or places where rodents may be present.
  • Avoid drinking milk or water that may have come in contact with rodents.
  • Drink pasteurized milk and water from safe sources.
  • Prevent rodent infestations in your home.
  • If you are bitten by a rat or think you may have rat-bite fever, consult with your healthcare provider.

If you handle rats or clean their cages:

  • Wear protective gloves.
  • Practice regular hand washing.
  • Avoid touching your mouth with your hands.

Rat-bite fever resources:


Last updated:  09/16/2014

Zoonotic Disease Program