Streptobacillus moniliformis Causes Rat Bite Fever in a Patient

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A 13 year-old-male presents to the Emergency Department (ED) with a 10-day history of headaches, fever and muscle pain (myalgia). Six days into the illness, he developed a diffuse, red, flat rash that did not appear on his palms. In addition, he had lower abdominal and suprapubic pain. One day prior to presenting to the ED, he noticed left shoulder and neck pain without any history of trauma. A bone scan was ordered to rule out osteomyelitis along with multiple laboratory diagnostic tests. A trans-esophageal echocardiogram (TEE) was ordered to rule out endocarditis. 

Lab Testing

Based on the patients’ clinical diagnosis, laboratory tests were ordered such as blood and urine cultures along with multiple serological tests (Cat Scratch Disease (CSD) (IgM & IgG), HIV 1/2, EBV, CMV, Parvovirus). Blood cultures at 5 days and urine culture were negative as were CSD and HIV serologies. EBV, CMV and Parvovirus serology results were indicative of past infection. Blood cultures were held for 14 days to rule out the presence of slow growing or fastidious organisms. The bone scan was negative, however the TEE was abnormal, suggesting endocarditis or inflammation of the heart chambers or valves. At day 7, the anaerobic blood culture was positive for gram-negative bacteria that showed a “cotton ball” appearance and bulbous swelling along fine filaments. Additional laboratory testing confirmed the identification of the organism to be Streptobacillus moniliformis. 

Cause of Symptoms

Streptobacillus moniliformis is the causative agent of rat bite fever. Rat bite fever is a zoonotic disease that is transmitted directly by rodents to humans either by a bite or scratch, or it can be passed rodent to rodent. A person can be at risk of developing the disease by ingesting contaminated food or water with rodent feces which is referred to as Haverhill Fever. An estimated 1 in 10 bites from a rat will result in this infection. Symptoms can include chills, fever, headache, vomiting and muscle aches. Joints can become swollen and pain can occur in the back. Ulcers on the skin can also develop.


Patient was treated with ampicillin/sulbactam and gentamicin but eventually changed to penicillin. The patient underwent an aortic root replacement and tissue debridement due to the diagnosis of endocarditis.  

Contact Information

Nicole Jackson,