Delayed Emergency Department Diagnosis of Rat-Bite Fever

Rat bite fever, caused by Streptobacillus moniliformis and Spirillum minus, is a zoonotic infection with increasing prevalence as more people keep rats as pets. It is a challenging diagnosis due to a broad range of symptomatology, and its causative organisms are difficult to culture. As such, it may be necessary to be diagnosed presumptively in the appropriate clinical context. This report details a case where diagnosis was presumptively made on a second emergency department presentation after no diagnosis was made on the first presentation. The patient in this case presented with fever, rash, and arthralgias, though presenting symptoms can vary from case to case. While treatable with penicillin or other antibiotics, it may lead to severe complications when diagnosis is delayed or failed. This patient was successfully treated with ceftriaxone followed by cephalexin (chosen due to a penicillin allergy) and made a complete recovery without complication. Taking a complete and thorough history is essential to ensuring that the diagnosis is made and that therapy is initiated in a timely manner.