Rat Bite Fever

Last Updated: August 2013 Importance Rat bite fever is a human illness that can be caused by two different bacteria, Streptobacillus moniliformis and Spirillum minus. Although this disease is readily cured with antibiotics, untreated infections are sometimes fatal. Both S. moniliformis and Sp. minus are acquired primarily from rodents, especially rats. At one time, rat bite fever was mainly a hazard of exposure to wild rats or laboratory rodents; however, pet owners, pet shop employees and veterinary staff may be at increased risk with the growing popularity of rodent pets. Clinical cases can be a diagnostic challenge, as the initial symptoms are nonspecific and there are few good, widely available, diagnostic tests. S. moniliformis is fastidious and can be difficult to isolate, while Sp. minus is uncultivable and can be identified only by its morphology. In animals, S. moniliformis is known mainly as a pathogen of rodents. This organism can cause septicemia, abscesses and arthritis in mice, and cervical lymphangitis or pneumonia in guinea pigs. Outbreaks in laboratory colonies can result in major economic losses, in addition to the zoonotic risks to personnel. Rare clinical cases or outbreaks have also been reported in other species of mammals and birds; however, the host range of S. moniliformis, and its effects on most animals, are still incompletely understood. Very little is known about Sp. minus infections in animals.