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Rat-bite fever

Rat-bite fever is a rare bacterial disease spread by infected rodents.


Rat-bite fever can be caused by 2 different bacteria, Streptobacillus moniliformis or Spirillum minus. Both of these are found in the mouths of rodents.

The disease is most often seen in:

  • Asia
  • Europe
  • North America

Most people get rat-bite fever through contact with urine or fluids from the mouth, eye, or nose of an infected animal. This most commonly occurs through a bite, yet some cases may occur simply through contact with these fluids.

A rat is usually the source of the infection. Other animals that may cause this infection include:

  • Gerbils
  • Squirrels
  • Weasels


Symptoms depend on the bacteria that caused the infection.

Symptoms due to Streptobacillus moniliformis may include:

  • Chills
  • Fever
  • Joint pain, redness, or swelling
  • Rash

Symptoms due to Spirillum minus may include:

  • Chills
  • Fever
  • Open sore at the site of the bite
  • Rash with red or purple patches and bumps
  • Swollen lymph nodes near the bite

Exams and Tests

This condition is diagnosed by detecting the bacteria in:

  • Skin
  • Blood
  • Joint fluid
  • Lymph nodes

Blood antibody tests and other techniques may also be used.


Rat-bite fever is treated with antibiotics for 7 to 14 days.

Outlook (Prognosis)

The outlook is excellent with early treatment. If it is not treated, the death rate can be as high as 25%.

Possible Complications

Rat-bite fever may cause these complications:

  • Abscesses of the brain or soft tissue
  • Infection of the heart valves
  • Inflammation of the parotid (salivary) glands
  • Inflammation of the tendons
  • Inflammation of the heart lining

When to Contact a Medical Professional

Call your health care provider if:

  • You or your child has had recent contact with a rat or other rodent
  • The person who was bitten has symptoms of rat-bite fever


Avoiding contact with rats or rat-contaminated dwellings may help prevent rat-bite fever. Taking antibiotics by mouth after a rat bite may also help prevent this illness.

Alternative Names

Streptobacillary fever; Streptobacillosis; Haverhill fever; Epidemic arthritic erythema; Spirillary fever; Sodoku


Washburn RG. Rat-bite fever:Streptobacillus moniliformisSpirillum minusPrinciples and Practice of Infectious Diseases

Update Date 12/7/2014

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