Streptobacillary Rat-Bite Fever

Streptobacillary rat-bite fever (RBF) is a systemic zoonosis caused by the aerobic Gram-negative bacterium Streptobacillus moniliformis and is transmitted to humans through the bites and scratches of infected rats.

Epidemiology

The disease is found worldwide, but the exact incidence is unknown.

Clinical description

High fever (up to 40 °C) is the first sign of infection (2-7 days after the bite) and is closely followed by chills, headache, nausea and vomiting. RBF is also associated with a morbilliform or purpuric rash of the extremities (in particular on the palms and the soles) and occasionally hemorrhagic vesicles on the hands and feet that may desquamate. Migratory polyarthralgia of the joints may also occur, generally leading to restricted movement. The bite typically heals quickly. In rare cases, complications are reported including endocarditis, pericarditis, myocarditis, diarrhea and degenerative changes in organs such as the kidneys and liver.

Etiology

The disease is generally contracted by the bites of infected rats and less often by other S. moniliformis hosts (gerbils, squirrels etc.>/i>). It can also be transmitted via ingestion of rat excrement through contaminated water, milk or food, in which case the contracted disease is called Haverhill fever. Streptobacillus moniliformis is predominantly present in the pharynx of the rats, but is also found in blood cultures and on arthritic or skin exudates.

Diagnostic methods

Diagnosis is based on characteristic growth, fatty acid profiles obtained by gas-liquid chromatography, blood antibody tests (agglutinating antibodies appearing from the 10th day) and to a lesser extent, on molecular detection of the germ.

Differential diagnosis

The differential diagnosis includes spirillary RBF (Sudoku; see this term) and several bacterial and viral infections (Lyme disease, leptospirosis, brucellosis, Rocky Mountain spotted fever, malaria, typhoid fever (see these terms), S. pyogenes and S. pyogenes-associated diseases, S. aureus infection, disseminated gonorrhea, meningococcemia, viral exanthemas, secondary syphilis, Epstein-Barr virus and coxsackieviruses).

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 carries a mortality rate of 13% due to complications.