Middle East DVEP - Armed Forces Pest Management Board

F. Relapsing Fever (tick-borne). (Endemic relapsing fever, also termed cave fever inthe Middle East)This is a systemic spirochetal disease characterized by periods of fever alternating withafebrile periods. The number of relapses varies from 1 to 10 or more. The severity ofillness decreases with each relapse. The duration of tick-borne relapsing fever is usuallylonger than the closely related louse-borne relapsing fever. A number of species ofBorrelia are responsible for the disease. The taxonomy of the pathogen is complex. Theclose vector-spirochete relationship has led to the definition of most spirochete species bythe tick vector. There is great strain variation among tick-borne Borrelia, and a singlestrain can give rise to many serotypes. Some authorities view all species as tick-adaptedstrains of the louse-borne relapsing fever spirochete, B. recurrentis.Military Impact and Historical Perspective. Although clinical symptoms of tickbornerelapsing fever can be severe, impact on military personnel would be minimal dueto low incidence of the disease.Disease Distribution. Sporadic cases are most often reported from Iran, Iraq, Israel,Jordan, Syria, Saudi Arabia and Yemen. Vector ticks commonly infest caves, bunkersand tombs.Transmission Cycle(s). Soft ticks of the genus Ornithodoros transmit tick-bornerelapsing fever. Infection is transmitted from human to human, animal to animal, or fromanimal to man by the bite of infective ticks. Rodents are sources of infection for ticks,although ticks are more important as a long-term reservoir. The pathogen has beenmaintained naturally in some species of ticks for years by transovarial transmission. Therate of transovarial transmission varies greatly among tick species. Ticks of both sexesand all active stages transmit the pathogen by bite or by infectious fluids exuded frompores in the basal leg segments. Spirochetes can pass into bite wounds or penetrateunbroken skin. Exposure to infected blood of patients can cause infections in medicalpersonnel.Vector Ecology Profiles.The primary vectors are Ornithodoros erraticus (Saudi Arabia, Israel), O. tholozani(Israel, Lebanon, Iran, Iraq, Jordan, Syria and Turkey), O. savignyi (Saudi Arabia,Yemen), and O. asperus (Iran). Ornithodoros erraticus and O. tholozani appear to besecondary vectors in Iran. Appendix A.3. lists species of ticks known from the MiddleEast.Ornithodoros erraticus is found in Saudi Arabia, Iran, Iraq, Israel, Lebanon, Syria, andTurkey. Ornithodoros savignyi occurs in Saudi Arabia and Yemen (Ta’izz and Hodeidaareas) in arid biotopes, especially under trees. It appears to be distributed through Iran toIndia. Ornithodoros tholozani is found in Israel, Jordan, Syria, Iran, Iraq, Lebanon, SaudiArabia, and Turkey. Ornithodoros asperus occurs in Iran.All of these tick species inhabit sheltered areas, such as caves, stables, and rockoutcroppings. Ornithodoros erraticus often inhabits rodent burrows. This species feeds83