Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 34-09: Rat-Bite Fever + Key Features Download Section PDF Listen +++ ++ Rat-bite fever is an uncommon acute infectious disease caused by Spirillum minus It is transmitted to humans by the bite of a rat Inhabitants of rat-infested dwellings, owners of pet rats, and laboratory workers are at greatest risk + Clinical Findings Download Section PDF Listen +++ ++ Rat bite heals promptly, but 1 to several weeks later the site Becomes swollen, indurated, and painful Assumes a dusky purplish hue May ulcerate Regional lymphangitis and lymphadenitis Fever, chills, malaise, and headache Myalgia, arthralgia, arthritis Splenomegaly A sparse, dusky-red maculopapular rash on the trunk and extremities After a few days, symptoms subside, only to reappear several days later Relapsing fever for 3–4 days alternating with afebrile periods lasting 3–9 days; may persist for weeks Endocarditis is rare complication + Diagnosis Download Section PDF Listen +++ ++ Leukocytosis Nontreponemal test for syphilis often falsely positive Organism may be identified in darkfield examination of the ulcer exudate or an aspirated lymph node Differential diagnosis Streptobacillary fever Tularemia Rickettsial disease (eg, Rocky Mountain spotted fever, epidemic typhus) Pasteurella multocida infection Relapsing fever + Treatment Download Section PDF Listen +++ ++ In acute illness, Intravenous penicillin 1–2 million units every 4–6 hours is given initially Ceftriaxone 1g intravenously daily is another option Once improvement has occurred, therapy may be switched to Oral penicillin V 500 mg four times daily for 10–14 days or Amoxicillin 500 mg three times daily for 10–14 days For the penicillin-allergic patient, tetracycline 500 mg orally four times daily or doxycycline 100 mg twice a day can be used Prompt diagnosis and antimicrobial treatment can markedly reduce the mortality rate (usually about 10%)