Rat Bite Fever in Pediatric Patients with Fever
A pediatric patient with fever following a rat bite should be treated with high-dose intravenous penicillin G (150,000-250,000 units/kg/day divided every 4-6 hours) for 10-14 days, as rat bite fever caused by Streptobacillus moniliformis is a potentially fatal systemic infection that requires prompt antibiotic therapy. 1, 2, 3
Immediate Recognition and Diagnosis
Maintain a high index of suspicion for rat bite fever in any febrile child with rodent exposure, even without a documented bite. 2, 3 The clinical presentation is highly variable and nonspecific, making diagnosis challenging:
- Classic triad: Fever, rash (maculopapular, petechial, or hemorrhagic pustules), and migratory polyarthritis 2, 4, 5
- Atypical presentations: May include subglottic masses, parotid swelling, or isolated fever without localizing signs 6
- Critical history: Specifically ask about pet rodents, rat exposure, or scratches—not just bites—as transmission can occur without actual bite wounds 3
Age-Specific Risk Assessment
The child's age significantly impacts your diagnostic and treatment approach:
- Infants <3 months: Have decreased immune function (reduced opsonin activity, macrophage function, neutrophil activity) and require more aggressive evaluation including sepsis workup and admission 7
- Children 3-36 months: Can be managed with closer observation if well-appearing, but rat bite fever remains a serious concern requiring treatment 7
Treatment Protocol
First-line therapy is high-dose intravenous penicillin G: 1
- Dosing: 150,000-250,000 units/kg/day divided every 4-6 hours
- Duration: Minimum 10-14 days (some cases require up to 4 weeks for endocarditis) 1, 6
- Alternative: Ceftriaxone has been used successfully when penicillin is unavailable or diagnosis is delayed 5
Critical pitfall: Tetracycline may produce initial response but has been associated with relapse; penicillin is superior for definitive cure 6
Monitoring and Complications
Watch for serious complications that require extended therapy: 1
- Endocarditis: Requires 4 weeks of treatment at 250,000 units/kg/day 1
- Arthritis: May need 7-10 days at 100,000 units/kg/day 1
- Bacteremia/septicemia: Requires full course despite clinical improvement 2, 3
Diagnostic Workup Considerations
While treating empirically, obtain appropriate cultures:
- Blood cultures: Essential but organism is fastidious and difficult to culture 4, 5
- Do not delay treatment waiting for culture confirmation given diagnostic difficulty and potential fatality 2, 3
Admission Criteria
Hospitalize for intravenous antibiotics if: 1, 2
- Systemic symptoms present (fever, rash, arthritis)
- Age <3 months with any fever following rat exposure 7
- Signs of serious bacterial infection or toxic appearance 8
Never assume a well-appearing child excludes serious infection—many children with rat bite fever initially appear well before decompensating 8, 2
Prevention Counseling
Provide hygiene education and prevention strategies regarding rodent handling and exposure to prevent recurrence 3