Rat-Bite Fever

Rat-bite fever (RBF) is a systemic bacterial zoonosis occurring in individuals that have been bitten or scratched by Streptobacillus moniliformis or Spirillum minus-infected rats and characterized by high fever, a rash on the extremities, and arthralgia.

Epidemiology

The exact incidence is unknown.

Clinical description

The clinical manifestations include high fever followed by headaches, chills, vomiting, a rash generally developing on the palms and soles, and symmetric polyarthritis of the joints that generally restricts movement.

Etiology

Most reported cases of rat-bite fever in the USA are caused by S. moniliformis (streptobacillary rat-bite fever), whereas in Asia the disease is mainly due to Spirillum minus (spirillary rat-bite fever; see these terms). Rat-bite fever is also contracted through contact with secretions of infected rats and less often through contact with other S. moniliformis and S. minus hosts, such as gerbils, mice and squirrels. In rare cases, the disease is transmitted through animal hosts such as dogs, cats and ferrets.

Diagnostic methods

Diagnosis is mainly based on the clinical symptoms, reported occurrence of a rat bite, clinical course and characteristic growth of the infectious agents in cultures from blood, synovial fluid or wound tissue.

Differential diagnosis

The differential diagnosis includes Haverhill fever (caused by S. moniliformis but transmitted via the consumption of water, milk or food contaminated by rat excrement; see this term) and several bacterial and viral infections (Lyme disease, leptospirosis, brucellosis, Rocky Mountain spotted fever (see these terms), S. pyogenes and S. pyogenes-associated diseases, S. aureus infection, disseminated gonorrhea, meningococcemia, viral exanthemas, and secondary syphilis).

Management and treatment

Management requires a prophylactic (avoiding direct or indirect contact with host animals) and therapeutic approach (local treatment and antimicrobial therapy). The most effective antibiotic treatment is penicillin G administration in non-allergic patients, and tetracycline and streptomycin in penicillin-allergic patients.

Prognosis

Prognosis is excellent if the disease is treated. If left untreated, RBF presents a mortality rate of approximately 10% due to complications.