A25.9 Rat-bite fever, unspecified

Name of the Condition

• Rat-bite fever, unspecified

Summary

Rat-bite fever, unspecified, is a bacterial infection transmitted through bites, scratches, or contact with secretions from infected rodents. The condition presents with systemic symptoms, including fever, rash, and localized inflammation at the exposure site. Onset typically occurs 3–10 days after contact, though timing may vary depending on the pathogen. The unspecified designation indicates the specific causative agent (e.g., Streptobacillus moniliformis or Spirillum minus) is not documented.

Causes

Rat-bite fever, unspecified, is caused by bacteria carried by rodents, such as rats or mice. Infection occurs when these bacteria enter the body through a bite, scratch, or contact with contaminated rodent urine, droppings, or nesting materials. The bacteria can also spread through handling of contaminated objects or surfaces.

Risk Factors

• Close contact with rodents (e.g., pet rats, wild mice)
• Occupational exposure (e.g., laboratory workers, pest control)
• Living in or traveling to areas with high rodent infestation
• Handling rodents without protective measures (e.g., gloves)
• Poor sanitation or storage of food that attracts rodents

Symptoms

• Sudden onset of fever (often with chills)
• Headache and muscle pain
• Rash (may be maculopapular or ulcerative)
• Swelling or redness at the site of rodent contact
• Lymph node enlargement near the exposure site
• Joint pain or stiffness

Diagnosis

Diagnosis is based on clinical presentation, exposure history, and laboratory testing. Blood cultures or wound swabs may identify the causative bacteria. Serologic tests or molecular methods (e.g., PCR) can confirm the infection, though results may take time. Clinical judgment is often required when specific pathogen details are unavailable.

Treatment Options

Treatment typically involves antibiotics, such as penicillin or doxycycline, tailored to the suspected pathogen. Supportive care, including rest and hydration, may be provided for symptom relief. Duration of therapy depends on severity and response to treatment.

Prognosis and Follow-Up

With prompt treatment, most patients recover fully. Follow-up may include monitoring for symptom resolution and potential complications. Untreated cases can lead to severe outcomes, especially in immunocompromised individuals.

Complications

• Septic arthritis
• Endocarditis
• Pneumonia
• Sepsis (in severe cases)

Lifestyle & Prevention

• Avoid contact with wild or pet rodents.
• Use protective gloves when handling rodents.
• Maintain clean living spaces to reduce rodent infestation.
• Store food in sealed containers to deter rodents.
• Seek prompt medical care for rodent bites or scratches.

When to Seek Professional Help

Consult a healthcare provider if you experience fever, rash, or other symptoms after rodent exposure, or if a rodent bite or scratch becomes infected.

Tips for Medical Coders

Use code A25.9 for rat-bite fever when the specific causative agent is not documented. Ensure documentation supports the diagnosis and exposure history. Verify that the code aligns with clinical findings and does not require a more specific code if details are available.