Rat bite fever presenting as localized cellulitis: The first documented presumptive case from Nepal and a call for...

Rat bite fever (RBF) is a rare but potentially fatal zoonotic disease caused by Streptobacillus moniliformis or Spirillum minus. In Asia, it is often caused by Spirillum minus and may present with atypical clinical features that complicate diagnosis.

A 35-year-old female from Far-Western Nepal developed fever and progressive localized swelling of the right hand eight days after a rat bite. Classic systemic features like rash, polyarthritis, and lymphadenopathy were absent. Laboratory tests showed neutrophilia, thrombocytopenia, and elevated CRP, while blood culture was negative. Despite negative microbiological result, a presumptive diagnosis of S. minus RBF was made based on epidemiological context, incubation period, and clinical presentation. She was treated with a combination of intravenous ampicillin, doxycycline and surgical wound debridement. She completed a course of oral antibiotics and recovered fully.

This case represents the first documented presumptive case of Spirillum minus RBF in Nepal, which presented atypically. It underscores the importance of clinical suspicion over microbiological confirmation in diagnosing RBF and emphasizes considering RBF in the differential diagnosis of febrile patients with cellulitis and a history of rodent exposure. Early initiation of empiric antibiotic therapy and timely surgical intervention can prevent serious complications. This case highlights RBF as an under-recognized zoonotic disease in Nepal and the need for greater clinical awareness and strengthened public health measures focused on rodent control.