Occupational Safety

Rat Bite Fever

Rat-bite fever is caused by either Streptobacillus moniliformis or Spirillum minor, two microorganisms that are present in the upper respiratory tracts and oral cavities of asymptomatic rodents, especially rats. These organisms are present worldwide in rodent populations, although efforts by commercial suppliers of laboratory rodents to eliminate Strep. moniliformis from their rodent colonies now appear to have been largely successful.

The form of the disease caused by Spirillum minor can be clinically different from the disease produced by moniliformis. Several cases of the disease in laboratory animal handlers have been reported in recent years.

Most human cases result from a bite wound inoculated with nasopharyngeal secretions, but sporadic cases have occurred without a history of rat bite. Infection also has been transmitted via blood of an experimental animal. Persons working or living in rat infested areas have become infected even without direct contact with rats.

In Strep. moniliformis infections, patients develop chills, fever, malaise, headache, and muscle pain. A rash, most evident on the extremities, follows. Arthritis occurs in 50% of Strep. moniliformis cases, but is considered rare in Spirillum minor infections. One or more large joints usually become painful and enlarged and contain a serous to purulent effusion. Complications of untreated cases of the disease include abscesses, endocarditis, and less frequently, pneumonia, hepatitis, pyelonephritis and enteritis.

Proper animal handling techniques are critical to the prevention of rat-bite fever.