Relapsing Fever


Cause: Spiral-shaped bacteria (spirochetes). Borrelia hermsii, B. parkeri, or B. turicatae for soft tick-borne relapsing fever, B. miyamotoi for hard tick-borne relapsing fever, and B. recurrentis for louse-borne relapsing fever.

Illness and treatment: Symptoms include a fever lasting 2 to 7 days cycling with afebrile periods of 4 to 14 days, with 1 to 10 cycles if untreated. Along with fever there may be shaking chills, sweats, headache, muscle or joint pain, or sometimes a rash. Treatment is with antibiotics.

Sources: The most common reservoirs in Washington for soft tick-borne relapsing fever appear to be wild rodents and Ornithodorus hermsii, a soft tick typically found in eastern parts of the state at higher altitudes (1500 – 8000 feet). The ticks live in rodent nests and inflict painless bites at night that are often unnoticed. Hard tick-borne relapsing fever also has rodent reservoirs with Ixodes pacificus and scapularis as vectors. Louse-borne disease is not endemic to the United States but may occur in travelers if an infective body louse contaminates a wound or mucous membranes.

Prevention: Avoid sleeping in rodent infested buildings in regions with endemic tick-borne disease. Rodent-proof structures to prevent future colonization by rodents and their soft ticks.

Recent Washington trends: Each year there are 1 to 12 reports of tick-borne relapsing fever cases. Most are associated with overnight stays in rustic summer cabins, but some are exposed in their primary homes. Louse-borne disease is rare, even in travelers; there have been no recent reports.

Purpose of Reporting and Surveillance

  • To educate potentially exposed persons about signs and symptoms of disease to facilitate early diagnosis and treatment.
  • To inform owners of potentially tick-infested property (example: a vacation cabin) how to reduce their risk of exposure.
  • To identify endemic geographic areas within Washington state.

Legal Reporting Requirements

  • Health care providers and Health care facilities: notifiable to local health jurisdiction within 3 business days
  • Laboratories: Borrelia hermsii, B. parkeri, B, turicatae, B. miyamotoi, or B. recurrentis notifiable to local health jurisdiction within 2 business days; submission on request – specimen associated with positive result, within 2 business days.
  • Local health jurisdictions: notifiable to Washington State Department of Health (DOH) Communicable Disease Epidemiology (CDE) within 7 days of case investigation completion or summary information required within 21 days.