Rat Bites: Signs, Treatment, and Rat-Bite Fever

Medically Reviewed By Cynthia Taylor Chavoustie, MPAS, PA-C

A bite from a rat could cause an infection known as rat-bite fever (RBF). Rat bites can transmit several diseases, but RBF could be fatal if not treated. Animal bites account for 1% Trusted Source PubMed Central Highly respected database from the National Institutes of Health Go to source of all U.S. emergency department visits. A rat bite can become infected and spread to other organs if left untreated. About 10% of rat bites become infected, leading to death in 10% of those infected.

This article explains a rat bite and how it can result in rat-bite fever (RBF). It also explains how to tell whether you have RBF and how to treat it.

What is a rat bite?

A pet rat holding onto its owner's finger
Clique Images/Stocksy United

Many people keep rats or other small rodents as pets. Rat bites are common when the animal is startled or threatened.

This is true for rats in the wild and rats people keep as pets. Children are more likely to startle animals in general, including rats, putting them at higher risk.

Up to 10% of rat bites can result in rat-bite fever (RBF). Infection may also be transmitted from other carnivores that prey on rats or rodents.

Without treatment, RBF has a 10% mortality rate.

What does a rat bite look like?

A picture showing two red marks on skin
Rat bites typically appear as small puncture wounds or a tear in the skin. Photo credit: © 2020 Faggion Vinholo et al.

A rat bite might look like a small puncture wound or tear of the skin, causing bleeding, swelling, and pain.

What is rat-bite fever (RBF)?

RBF is a bacterial infection that can be fatal if untreated.

Signs and symptoms develop 3–10 days after the bite. The infection can spread to the lungs, heart, and other organs without treatment.

There are two types of RBF:

  • Spirillary RBF results from the bacteria Spirillum minus.
  • Streptobacillary results from the bacteria Streptobacillus moniliformis.

Read more about bacterial infections.

What are symptoms of rat-bite fever?

If rat bites tear the skin, RBF symptoms may develop 3–10 days after exposure.

RBF symptoms may include:

Streptobacillary rat-bite fever

Streptobacillary RBF comes from the Streptobacillus moniliformis bacteria and is usually found in the United States and Europe.

The wound can initially heal, but the infection may incubate for 1–22 days. Symptoms such as fever, vomiting, and rashes on the hands and feet can develop.

Although rare, other complications may develop, including:

  • septic arthritis, an infection in the joint fluid and tissues
  • bacterial endocarditis, bacteria entering the bloodstream and traveling to the heart
  • abscesses in the brain


Spirillary rat-bite fever

In spirillary RBF, the symptoms usually appear Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source within 7–10 days but may appear as early as 2 days. However, they may also take up to 3 weeks to appear.

Other symptoms include an urticarial rash, which is similar to hives.

Also, symptoms can resemble other conditions, which can delay diagnosis. Be sure to contact healthcare professionals about a rat bite.

When should you see a doctor?

Seek prompt medical care if the bite is bleeding profusely with no signs of stopping. You should also contact a doctor if you have a weakened immune system due to medications, cancer, HIV, diabetes, or other medical conditions.

Seek immediate medical care if you develop RBF symptoms or if the wound appears infected. Infection may present as increasing pain, redness of the area bitten, warmth, or a fever.

What are the causes and risk factors of a rat bite?

Animals, including rats, bite when they are threatened, surprised, or startled. Rat bites can transmit several diseases, but rat-bite fever is the main concern.

Risk factors Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source for rat bites and RBF include:

  • those who have pet rats or other rodents in their home
  • those who work with rats or other rodents, such as in a pet store, zoo, or research laboratory
  • those who live or spend time in areas with rodent infestations

People with weakened immune systems are at a higher risk of complications, including infections, from rat bites. This includes people with:

It also applies to people who take medicines to suppress their immune system, pregnant people, and older adults. Children younger than 5 years old also have a higher risk of infection because their immune systems may not be fully developed.

Reducing your risk of a rat bite

To reduce the risk of a rat bite, monitor children near animals, including pets. Everyone around animals should follow these rules to avoid startling or threatening situations:

  • Handle animals gently.
  • Leave them alone when they are eating or feeding their young.
  • Never tease an animal.

Reducing your risk of rat-bite fever

Always wash your hands after handling a rat or its cage, bedding, urine, or droppings. If you are bitten by a rat, washing the wound with soap, and large amounts of water may flush germs out and reduce your risk of RBF.

Reducing your risk of an animal bite

  • Always handle animals gently.
  • Leave them alone when eating, feeding their young, or making it clear they feel afraid.
  • Try not to disturb them when they are sleeping.
  • Never tease an animal.
  • Make sure they can see you before you touch or pick them up.
  • Try not to kiss or hold small animals, such as rodents, near your face.

How do you treat rat bites and rat-bite fever?

Immediate rat bite treatment involves thoroughly washing the wound with soap and large amounts of water. Use clean gauze or a towel to apply pressure if the wound is bleeding.

Use an ice pack to help reduce swelling and pain. Contact your doctor to see whether you need to make an appointment.

Treating rat-bite fever

Your doctor may use antibiotics such as penicillin if they suspect you have RBF. People allergic to penicillin may be administered doxycycline instead.

Antibiotics are highly effective at curing RBF\, particularly if the treatment starts soon after you become sick, according to the Centers for Disease Control and Prevention (CDC) Trusted Source Centers for Disease Control and Prevention (CDC) Governmental authority Go to source .

How do doctors diagnose a rat bite?

Diagnosing a rat bite relies on your ability to identify the animal. Diagnosing RBF can be challenging. The symptoms are nonspecific and resemble many other systemic illnesses.

It’s also difficult to culture, or grow, the bacteria that cause RBF. These issues can delay a diagnosis unless you communicate about a recent bite, even a suspected or potential rat bite.

Your doctor may diagnose a rat bite or RBF using the following:

  • evaluating the size of the bite
  • checking your joints and joint fluid for septic arthritis
  • checking your skin for rashes, particularly on the hands and feet

What are the potential complications of a rat bite?

Infection, particularly with RBF, is the main complication of a rat bite. Most people recover from RBF with proper treatment.

Left untreated, RBF is fatal in 10% of cases.

Frequently asked questions

Cynthia Chavoustie, MPAS, PA-C, has reviewed the following frequently asked question.

Does a rat bite require a vaccination?

Rat bites and other animal bites require a tetanus vaccination but rarely is a rabies vaccination required.

Summary

Rat bites can occur when handling, touching, or being near a rat or rodent. The main concern is rat-bite fever, which can develop shortly after a bite. Symptoms of RBF include headache and nausea. If left untreated, RBF could be fatal.

However, if treated quickly, antibiotics clear the infection from the bite. If you have a bite from a rat or rodent, even a suspected bite, seek prompt medical advice.

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Medical Reviewer: Cynthia Taylor Chavoustie, MPAS, PA-C
Last Review Date: 2022 Oct 28
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