Streptobacillus moniliformis

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Streptobacillus moniliformis / (Redirected from Haverhill fever)

Background

Microbiology

  • Pleomorphic, non-motile, non-sporulating, non-encapsulated filamentous Gram-negative bacillus
    • Often long, but can even be coccoid
    • Lateral bulbar swellings
  • Anaerobic, requires 8-10% CO2 to grow in culture, and requires an enriched medium
    • Blood cultures often negative because it is inhibited by SPS in blood culture bottles
  • Nonhemolytic cotton-like colonies on blood agar
  • Forms small flocculent puffballs in liquid media
  • Can form a penicillin-resistant, cell-wall-deficient L-phase variant
    • "Fried egg" appearance on plate

Epidemiology

  • Transmitted by the bite or scratch (or sometimes merely handling) of a rat, mouse, guinea pigs, or squirrel, or of an animal that eats these (e.g. dog, cat, pig, ferret, weasel, or python)
    • Oral flora of these animals
  • Can have occupational exposures in a labs or pet stores, household exposure due to rat infestation, or exposure from pet rats
    • 50% of cases are in children
    • Occurs in about 10% of rat bites, though only 200 cases reported in the US
  • Can also be acquired by ingestion of turkey, or milk or water contaminated with rat feces
    • Milk outbreak in Haverhill, MA, gives it its name of Haverhill fever

Pathophysiology

  • Likely gains access through a broken skin (or mucosal) barrier
  • Relapses may be related to spontaneously changing to and from the L variant
  • Autopsy shows erythrophagocytosis, hepatosplenomegaly, interstitial pneumonia, and lymph node sinus hyperplasia

Clinical Manifestations

  • Incubation period 10 days (range 1 to 22 days)
  • Fever, chills, headache, nausea/vomiting, severe migratory arthralgias and myalgias
    • Wound has often healed by presentation
  • Significant leukocytosis
  • Can have false-positive non-treponemal syphilis serology
  • After 2 to 4 days, develops a nonpruritic rash that can be maculopapular, morbilliform, petechial, vesicular, or pustular, on extremities
    • May become purpuric and confluent
    • Involves palms and soles
  • Arthralgias progress to arthritis
  • Fever resolves within days, and the other symptoms within about 2 weeks
  • However, can develop a relapsing-remitting course over months, and arthritis can persist for years

Haverhill Fever

  • When acquired from oral ingestion, can present with pharyngitis and severe vomiting, then progress to the usual

Rare Sequelae

Diagnosis

  • Often on the differential with leptospirosis, and can mimic RMSF, secondary syphilis, gonococcal infection, Lyme disease, brucellosis, septic arthritis, and other
  • On microscopy, the bacilli stain with Giemsa, acridine orange, or Gram stain
  • Must be cultured with specific enriched media
  • ELISA exists for antibodies, and PCR exists

Treatment

  • Penicillin G 12 million units total daily dose IV, step down to oral after a week if well
  • Alternative: tetracycline 500 mg po q6h, streptomycin 7.5 mg/kg IM q12h
  • Duration 10 to 14 days

Prevention

  • Rat bites should be cleansed thoroughly
  • Tetanus prophylaxis if appropriate
  • Can do 3 days of prophylactic penicillin 2 g daily divided

Further Reading

  • Rat Bite Fever and Streptobacillus moniliformis. Clin Microbiol Rev. 2007;20(1):13-22. doi: 10.1128/CMR.00016-06