What is the treatment for a bite from a sewer rat (Rattus norvegicus)?

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From the Guidelines

If you've been bitten by a sewer rat, seek immediate medical attention at an emergency room or urgent care center, where the wound should be thoroughly cleaned and antibiotics administered to prevent infection, as recommended by the Infectious Diseases Society of America in 2014 1. The wound should be cleaned with soap and water for at least 5 minutes before medical care. Healthcare providers will likely clean the wound more extensively, possibly debride damaged tissue. Some key points to consider in the treatment of a sewer rat bite include:

  • Thorough wound cleansing to reduce the risk of bacterial infection, as emphasized in the 2008 recommendations of the Advisory Committee on Immunization Practices 1
  • Administration of antibiotics, such as amoxicillin-clavulanate (Augmentin) 875/125 mg twice daily for 5-7 days, or alternatives like doxycycline 100 mg twice daily if you have penicillin allergies, as recommended in the 2014 guidelines for the diagnosis and management of skin and soft tissue infections 1
  • Consideration of a tetanus booster (Tdap) if you haven't had one in the past 5 years
  • Monitoring for signs of infection, including increasing redness, swelling, warmth, pus, fever, or red streaking from the wound, and returning for care immediately if these develop
  • Keeping the wound clean and dry after treatment, changing bandages as directed by your healthcare provider. It's also important to note that rat bites carry significant infection risks from bacteria like Streptobacillus moniliformis and Spirillum minus, which can cause rat-bite fever, as well as other pathogens including Pasteurella, and that sewer rats may carry additional contaminants 1.

From the Research

Treatment for Bite from Sewer Rat

  • The treatment for a bite from a sewer rat includes good surgical management and avoidance of prophylactic antibiotics due to a low natural infection rate 2.
  • If the wound becomes infected, a cephalosporin or penicillinase-resistant penicillin should be sufficient for treatment with appropriate surgical care of the wound 2.
  • Tetanus prophylaxis is mandatory because most patients are deficient in this regard 2.
  • Rabies prophylaxis is usually not required 2.

Infection Risk and Management

  • Bacterial isolates were cultured from 30% of rat bite wounds, with Staphylococcus epidermidis being the most common isolate 2.
  • Rat bite fever is a rare disease with a potentially lethal course, and timely antibiotic administration is crucial to prevent an unfavorable outcome 3.
  • In cases of persistent fever, blood culture sampling should be performed even in the absence of a systemic inflammatory response, and a bacterial 16S ribosomal RNA PCR on blood or joint aspiration (cultures) is an even more sensitive diagnostic test 3.

General Management and Prophylaxis

  • Copious irrigation may be the most important aspect of wound care, and early initiation of antimicrobial therapy can decrease morbidity and mortality, particularly in patients at high risk for infection 4.
  • Patient education is important for decreasing the incidence and morbidity of animal bites, and a patient's tetanus status and risk of rabies must be identified and appropriate immunoprophylaxis administered 4.
  • Managing bite wounds can be challenging, and providers must consider the patient's tetanus status, species of animal inflicting the bite, and infection risk 5.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Rat bites: fifty cases.

Annals of emergency medicine, 1985

Research

Rat bite fever: a case report review.

Acta clinica Belgica, 2022

Research

Management and treatment of animal bites.

JAAPA : official journal of the American Academy of Physician Assistants, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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