Rat-bite fever is a rare bacterial disease spread by the bite of an infected rodent.
Streptobacillary fever; Streptobacillosis; Haverhill fever; Epidemic arthritic erythema; Spirillary fever; Sodoku
Rat-bite fever can be caused by either of 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:
- 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 or scratch. 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:
Symptoms depend on the bacteria that caused the infection.
Symptoms due to Streptobacillus moniliformis may include:
- Joint pain, redness, or swelling
Symptoms due to Spirillum minus may include:
- Open sore at the site of the bite
- Rash with red or purple patches and bumps
- Swollen lymph nodes near the bite
Symptoms from either organism usually resolve within 2 weeks. Untreated, the symptoms, such as fever or joint pain, can keep returning for many weeks or longer.
Exams and Tests
The health care provider will perform a physical examination and ask about your symptoms. If the provider suspects rat bite fever, tests will be done to detect the bacteria in:
- 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.
The outlook is excellent with early treatment. If it is not treated, the death rate can be as high as 25%.
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 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.
Shandro JR, Jauregui JM. Wilderness-acquired zooneses. In: Auerbach PS, ed. Auerbach's Wilderness Medicine. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 34.
Washburn RG. Rat-bite fever: Streptobacillus moniliformis and Spirillum minus. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 233.