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Overview

What Is Rat-Bite Fever?

Rat-bite fever is a bacterial infection linked to infected rats and other rodents. It can follow a rat bite, scratch, contact with rodent saliva or urine, or exposure to contaminated food or materials. Symptoms can develop after an injury that seems minor or even after there is no obvious wound. Medical evaluation matters because untreated rat-bite fever can spread and become serious.

Symptoms

Symptoms of Rat-Bite Fever

Symptoms may begin days to weeks after exposure and can vary from person to person. Not seeing an obvious wound does not rule out infection after being bitten by rats or exposed to rodents.

  • Fever
  • Vomiting
  • Headache
  • Muscle pain (myalgia)
  • Joint pain (arthralgia)
  • Rash
  • Swollen joints (arthritis)

After a rodent exposure

Watch for infection symptoms

Fever, rash, or joint pain after a rat or mouse bite, scratch, or close exposure warrants prompt medical advice. Contact a clinician even if the original injury looked small.

How It Spreads

How Rat-Bite Fever Spreads

Rat-bite fever bacteria may be carried by rats, mice, and other rodents. The bacteria can enter through broken skin or mucous membranes, including the eyes, nose, or mouth.

  • Bites can transfer bacteria from an infected rodent into broken skin.
  • Scratches can introduce bacteria from a rodent’s claws or contaminated body fluids.
  • Contact with rodent saliva or urine can spread bacteria through broken skin or mucous membranes.
  • Touching contaminated surfaces, bedding, or other materials can result in exposure.
  • Eating or drinking contaminated food or water can transmit the infection.

Risk Factors

Risk Factors for Rat-Bite Fever

  • Living in or visiting places with rodent infestations increases the chance of contact with infected animals or contaminated materials.
  • Handling pet or laboratory rodents can lead to bites, scratches, or contact with body fluids.
  • Working in animal care, pest control, or rodent research may involve repeated exposure.
  • Homelessness or crowded housing can make it harder to avoid rodents and maintain safe food storage.
  • Cleaning areas contaminated by rodents without gloves, ventilation, and careful hand hygiene increases exposure risk.

Some exposure-related risks can be reduced by controlling infestations, using protective equipment, and avoiding direct contact. However, anyone can develop rat-bite fever after exposure, including someone who does not usually handle rodents.

Complications

Complications of Rat-Bite Fever

Untreated rat-bite fever can spread beyond the initial exposure site and may become serious, particularly in infants, older adults, and people with weakened immune systems.

  • Infection of the heart valves or the lining around the heart can occur.
  • Inflammation of the brain or spinal cord can cause serious neurologic illness.
  • Pneumonia may develop when the infection affects the lungs.
  • Abscesses can form in infected tissues.
  • Severe joint inflammation can cause significant pain and reduced movement.

Seek urgent care

Serious symptoms need immediate evaluation

Seek urgent medical care for confusion, severe headache, breathing difficulty, chest pain, fainting, rapidly worsening illness, or persistent high fever after rodent exposure.

Diagnosis

How Rat-Bite Fever Is Diagnosed

Clinicians may ask about rat or mouse bites, scratches, handling rodents, contaminated food or water, and when symptoms began. They also consider the physical examination, including fever, rash, swollen joints, and other findings.

  • Blood or other specimen testing may look for evidence of the bacteria or infection.
  • Bacterial culture may be used when an appropriate specimen is available.
  • Evaluation for complications may include additional tests when symptoms are severe.

Treatment & Management

Treatment and Management of Rat-Bite Fever

Rat-bite fever requires prescription antibiotics, and treatment should begin promptly when the infection is suspected. A clinician chooses the appropriate medicine based on the person’s symptoms, health history, and test results; do not try to treat the infection with leftover medication.

  • A healthcare professional should clean and assess the wound after a rat or mouse bite or scratch.
  • Prescribed antibiotics treat the bacterial infection.
  • Clinicians monitor for complications and provide additional care if the illness is severe.
  • Tetanus protection should be updated when indicated.
  • The full prescribed medication course should be completed, even if symptoms improve.

Medical care

Prompt treatment helps prevent complications

Contact a healthcare professional after a rat or mouse bite or scratch, especially if fever, rash, vomiting, or joint symptoms develop.

Prevention

How to Prevent Rat-Bite Fever

  • Seal gaps, cracks, and other entry points that allow rodents into buildings.
  • Store food securely and clean up spills and crumbs promptly.
  • Remove clutter that can provide rodents with hiding or nesting places.
  • Use gloves during cleanup, follow safe cleaning practices, and wash hands afterward.
  • Avoid touching wild rodents or trying to handle them with bare hands.
  • Seek professional help for significant or persistent rodent infestations.

After a bite or scratch, wash the area thoroughly with soap and running water. Avoid handling the animal, and contact a healthcare professional about wound infection, tetanus protection, and any needed public-health advice. Although questions such as whether a rat can carry rabies are common, medical assessment should focus on all possible risks from the exposure.

Outlook and Prognosis

Outlook and Prognosis for Rat-Bite Fever

With prompt antibiotic treatment, most people recover from rat-bite fever. Recovery time varies depending on how severe the illness is and whether complications have developed. Without treatment, the infection can become severe.

When Should You See a Doctor

When Should You See a Doctor?

  • Seek medical advice after any rat or mouse bite or scratch.
  • Contact a clinician if fever or a rash develops after rodent exposure.
  • Get care for worsening redness or swelling around a wound.
  • Have a draining wound assessed by a healthcare professional.
  • Seek advice for vomiting or severe joint pain after exposure.
  • Contact a clinician promptly if you have a weakened immune system and have been exposed.

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