Rat-bite fever

Rat-bite fever is a bacterial infection caused by either Streptobacillus moniliformis or Spirillum minus. Both infections are rare with streptobacillosis more common in the Americas and Europe and spirillosis more common in Asia and Africa. At risk are handlers of laboratory or pet rats.

CASES/YEAR
20 (US); 400 (Global)
CATEGORY
Zoonoses
AGENT TYPE
Bacteria
OTHER NAMES
Streptobacillosis (Streptobacillary fever, Haverhill fever, Epidemic arthritic erythema, Rat-bite fever due to Streptobacillus moniliformis); Spirillosis (Spillary fever, Soduku, Rat-bite fever due to Spirillum minus); Ratbite fever;
ACUITY
Acute-Severe
INCUBATION
3-10 days with a range of 2 days to 3 weeks; (streptobacillosis); 7-21 days with a range of 1 day to 6 weeks (Spirillosis); [CCDM]
INITIAL SYMPTOMS
Flu-like illness followed within 2-4 days by a rash (maculopapular rash prominent on the extremities or reddish/purplish plaques; [CCDM, p. 509]
PRECAUTIONS
Standard; "Not transmitted from person to person." [CDC 2007 Guideline for Isolation Precautions]
COMMENTS
EPIDEMIOLOGY:
Rat-bite fever is a bacterial infection caused by either Streptobacillus moniliformis or Spirillum minus. Both infections are rare with streptobacillosis more common in the Americas and Europe and spirillosis more common in Asia and Africa. At risk are handlers of laboratory or pet rats. Rarely, infections have also been reported after bites by squirrels, and gerbils, and mice. Also, cats, dogs, ferrets, and weasels may carry infection after hunting rats. The case-fatality rates (untreated) are about 10%. [CCDM, p. 509] S. moniliformis can be cultured from the mouths or nasopharynx of more than 50% of rats. Common-source outbreaks of S. moniliformis infections (Haverhill fever) transmitted by contaminated food, milk, or water have been described. Thirteen cases of human infections were reported in the USA between 1958 and 1983. Most S. minus infections are reported in Asia. Only one case has been reported in the USA in the past 31 years. [ID, p. 1736] S. minus is not transmitted by contaminated food or water. [ABX Guide: Streptobacillus moniliformis]

FINDINGS:
Patients present with a history of a rat bite, followed by fever and rash. In streptobacillosis, a maculopapular rash prominent on the extremities appears 2-4 days after onset of the fever. Non-suppurative polyarthritis is common in streptobacillus infections. Other complications of both infections are endocarditis, pericarditis, parotitis, tenosynovitis, and abscesses of the skin and brain. The rash of spirillosis is described as reddish or purplish plaques. Unique to spirillosis is an ulcerated lesion at the site of the rat bite. [CCDM, p. 508]

Ulceroglandular syndrome (ulceration of the bite site, lymphangitis, and regional lymphadenitis) is a feature of infections by Spirillum minus but not S. moniliformis. In S. minus infections, arthritis is rare, and urticaria is sometimes seen. The rash caused by S. moniliformis may be petechial, vesicular, or pustular. Patients with either infection may have leukocytosis and recurrent fever. Patients with Haverhill fever may have pharyngitis, nausea, and vomiting. Syphilis serology is positive in up to 25% of patients with S. moniliformis and up to 50% of patients with S. minus. Complications of S. moniliformis infection are endocarditis, myocarditis, pericarditis, meningitis, anemia, and pneumonia. Hepatitis, splenomegaly, pleural effusions, epididymitis, and conjunctivitis have been reported as complications of S. minus infections. [PPID, p. 2804-5]
DIAGNOSTIC
S. moniliformis: Culture (maintain for 10 days after inoculation); [CCDM] Spirillum minus: see spirochetes by microscope; Xenodiagnosis; [PPID] S. moniliformis: Gram or Giemsa stain of blood cx isolate, joint fluid, or pus; Culture; [ABX Guide]
SCOPE
Global
SIGNS & SYMPTOMS
  • >arthralgia
  • >fever
  • >fever, biphasic or relapsing
  • >myalgia
  • E pharyngitis
  • G diarrhea
  • G nausea, vomiting
  • H anemia
  • H leukocytosis
  • H lymphadenopathy
  • H splenomegaly
  • N headache
  • O conjunctivitis, acute
  • S entry wound with lymph nodes
  • S lymphadenitis, acute
  • S lymphangitis
  • S papules or plaques
  • S petechiae and ecchymoses
  • S pustule
  • S rash (exanthem)
  • S rash on palms
  • S skin blister or vesicles
  • S ulcer of skin
  • S urticaria
  • X pleural effusions
  • *arthritis
  • *brain abscess or lesion
  • *endocarditis
  • *epididymo-orchitis
  • *hepatitis
  • *meningitis
  • *myocarditis
  • *parotitis
  • *pericarditis
  • *pneumonia
  • *sepsis
  • *weight loss
ANTIMICROBIC

Yes

VACCINE

No

ENTRY
Inhalation, Ingestion, Animal Bite
SOURCE
Animal Excreta, Eating Contaminated Food, Eating Contaminated or Infected Meat, Eating Unpasteurized Milk or Cheese, Waterborne (Ingesting, Inhaling, or Swimming)
RESERVOIR
Cats, Dogs, Rodents, Swine, Wild Animals
RISK FACTORS
  • Handle infected laboratory rats or mice
  • Handle infected rodents (bite)
  • Handle infected rodents (not bite)
  • Ingest infectious agents in food/water
  • Raise dust of excreta from rodents
DRUG LINK
Merck Manual: Rat-Bite Fever
REFERENCES FOR CASES/YEAR
1. (US) Rat bite fever is rare in the US--about 1-2 cases per year; [PMID 15635289] A PubMed search for "Spirillum minus" finds a few case reports in the last several decades. Assume 20 cases/year for US;
2. (Global) Rarely reported in England or Wales--about 1-2 cases per year by S. moniliformis; Spirillum minus is also rare and reported only in Asia; [Public Health England website] Guesstimate: global cases/yr = 20 times US cases/yr;