## Fatal Rat-Bite Fever --- Florida and Washington, 2003

Rat-bite fever (RBF) is a rare, systemic illness caused by infection with Streptobacillus moniliformis. RBF has a case-fatality rate of 7%--10% among untreated patients (1). S. moniliformis is commonly found in the nasal and oropharyngeal flora of rats. Human infection can result from a bite or scratch from an infected or colonized rat, handling of an infected rat, or ingestion of food or water contaminated with infected rat excreta (1). An abrupt onset of fever, myalgias, arthralgias, vomiting, and headache typically occurs within 2–10 days of exposure and is usually followed by a maculopapular rash on the extremities (1). This report summarizes the clinical course and exposure history of two rapidly fatal cases of RBF identified by the CDC. Unexplained Deaths and Critical Illnesses (UNEX) Project in 2003. These cases underscore the importance of 1) including RBF in the differential diagnoses of acutely ill patients with reported rat exposures and 2) preventing zoonotic infections among persons with occupational or recreational exposure to rats.

## Case Reports

Florida. In early September 2003, a previously healthy woman aged 52 years visited an emergency department (ED) with a 2-day history of headache, abdominal pain, diarrhea, lethargy, right axillary lymphadenopathy, progressive myalgias, and pain in her distal extremities. On physical examination, she was afebrile and hypotensive (blood pressure: 82/40 mmHg) with left-sided abdominal tenderness and scleral icterus; no rash was noted. Laboratory tests indicated a mildly elevated white blood cell count of 13,800 cells/ $ \mu $ L (normal: 5,000--10,000 cells/ $ \mu $ L), thrombocytopenia (71,000 platelets/ $ \mu $ L [normal: 130,000--500,000 platelets/ $ \mu $ L]), elevated alanine aminotransferase of 112 U/L (normal: 20--52 U/L), elevated aspartate aminotransferase of 154 U/L (normal: <40 U/L), elevated total bilirubin of 5.8 mg/dL (normal: 0.2--1.2 mg/dL), elevated blood urea nitrogen of 55 mg/dL (normal: 7--23 mg/dL), and elevated creatinine of 2.9 mg/dL (normal: 0.7--1.5 mg/dL).

The patient was admitted to the intensive care unit, where she became increasingly hypoxic with marked anemia (hemoglobin: 8.6 g/dL [normal: 12–16 g/dL]) and increasingly severe thrombocytopenia (32,000 platelets/ $ \mu $ L). She was treated with ciprofloxacin, metronidazole, and vancomycin for possible gram-negative sepsis and received two blood transfusions; however, she died approximately 12 hours after admission. A maculopapular rash was noted postmortem. No autopsy was performed.

Peripheral blood smears obtained before death revealed abundant neutrophils and intracellular collections of filamentous bacteria (Figure). Premortem blood from a tube containing no additives or separators was inoculated onto a blood agar plate and incubated in $ CO_{2} $ at $ 95^{\circ}F $ ( $ 35^{\circ}C $ ). After 72 hours, the culture demonstrated slight growth of gram-negative filamentous bacteria. UNEX was contacted for assistance, and diagnostic specimens were submitted to CDC for further laboratory evaluation. At CDC, the isolate was subcultured onto media enriched with 20% solution of sterile normal rabbit serum and incubated in a candle jar for 48 hours. Biochemical analyses identified the bacterial isolate as S. moniliformis. The 16S rRNA gene sequences