Cause: Spiral-shaped bacteria (spirochetes). Borrelia hermsii for 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 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. 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 (e.g., a vacation cabin) how to reduce their risk of exposure.
- To identify endemic geographic areas within Washington state.
Legal Reporting Requirements
- Health care providers: notifiable to local health jurisdiction within 24 hours
- Health care facilities: notifiable to local health jurisdiction within 24 hours
- Laboratories: Borrelia hermsii or recurrentis notifiable to local health jurisdiction within 24 hours. Specimen submission is on request only. Submission of specimens for other Borrelia species that cause relapsing fever may also be requested.
- 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.