What to Know About Rat Bite Fever

Medically Reviewed by Carol DerSarkissian, MD on May 27, 2023
4 min read

Rats are common pests in all parts of the world. They can cause property damage by chewing and burrowing. They also carry dangerous diseases that affect humans. One such sickness is rat bite fever.

Rat bite fever is caused by bacteria that live inside rats’ mouths. The bacteria can transfer to people through a bite or a scratch. In some cases, contact with rodent droppings can pass the bacteria along. The disease can be cured with antibiotics. It can lead to severe complications or death without treatment.

Learn more about rat bite fever and if you are at risk for it.

Two types. Rat bite fever is the term used for infections by two different bacteria that rats carry. The first is streptobacillus moniliformis, which leads to streptobacillary rat bite fever. The second is called spirillum minus, which causes spirillary rat bite fever. This is also sometimes known as sodoku. 

Only streptobacillary rat bite fever has been reported in the United States. Spirillary rat bite fever is found in Asia.

Bacteria, not rats. The name rat bite fever is a bit misleading. Rats are only carriers of the bacteria that cause it. Other rodents such as mice, squirrels, guinea pigs, and gerbils can carry them as well. 

Animals like dogs or cats can also carry the bacteria if they have been in close contact with infected rodents or their droppings. Animals carry the bacteria as hosts. They typically don’t show any symptoms.

Bites and scratches. People get rat bite fever if an infected rat or other rodent bites or scratches them. Rodents can also shed the bacteria in their feces. Their droppings can pass the illness to humans. It’s also possible to get rat bite fever from eating food that has been contaminated with an infected animal’s saliva, urine, or feces.

The most significant risk for rat bite fever is exposure to rats or other rodents. Rat bite fever does not pass from person to person. The only way for you to get it is from an infected animal.

People most likely to get rat bite fever include:

  • People with pet rats or other rodents in their home
  • People who keep rats or other rodents to feed to other animals
  • People who work in places like research laboratories or pet stores where they have contact with rats or other rodents
  • People who live in areas with sizable wild rat or mouse populations.
  • Older adults 
  • People who are pregnant
  • People with weakened immune systems

Young children who are around rodents are at higher risk for rat bite fever than adults. Their immune systems are still developing. They may be less able to fight off the illness. 

If you have young children who have contact with rodents, you can reduce their risk by making sure they wash their hands after touching them. Quickly clean any bites or scratches.

Contact your doctor immediately if you have been around rodents and have any symptoms of rat bite fever. Rat bite fever can be life-threatening. Quick treatment is critical to recovering from the infection.

Streptobacillary rat bite fever. Symptoms of streptobacillary rat bite fever usually show up 3 to 10 days after you have been exposed to the bacteria. A bite or scratch will probably be healed by the time you feel any symptoms. Common symptoms include:

  • Headache
  • Fever
  • Rash
  • Vomiting
  • Muscle pain
  • Joint pain or swelling

You may develop infections in internal organs such as your lungs, liver, or brain if streptobacillary rat bite fever isn’t treated. These complications are very serious. They can result in death without immediate treatment.

Spirillary rat bite fever (sodoku). Symptoms of spirillary rat bite fever tend to appear 7 to 21 days after exposure to the bacteria. You may notice changes to the actual bite or scratch. Other symptoms include:

  • Intermittent fever
  • Swollen lymph nodes
  • Rash
  • Swelling or sores near the wound‌

Early detection and swift treatment are critical for rat bite fever. It can lead to death if it is left untreated. 

Antibiotics are very effective at curing the illness. Talking to your doctor soon after possible exposure will help you get prompt treatment if you need it.

Clean the wound well with soap and water if you are bitten or scratched by any rodent. Call your doctor and let them know a rodent scratched or bit you. Your doctor will know when to begin treatment for rat bite fever if you develop any symptoms.

Talk to your doctor if you have any questions about your risk of rat bite fever.