An outbreak of spotted fever rickettsiosis in U.S. Army troops deployed to Botswana.

Novel infectious diseases are recognized when nonimmune persons move into the ecologic niche of a pathogen and become inadvertent hosts. One population at frequent risk to such emerging pathogens is the military. Historical examples of this phenomenon include outbreaks of scrub typhus during World War II and Korean hemorrhagic fever during the Korean War (1). In this report, we describe a modern example as we document an unusually high attack rate of a rickettsial disease among U.S. troops camping for a brief period in Af-rica. In January 1992, U.S. soldiers participated in a 10-day training exercise with the Botswana Defense Force near Shoshong, Botswana. Activities included individual weapons' training and a series of mock battles. The terrain was generally flat with scattered bushes and small trees. The climate was semiarid, and temperatures reached 120°F during the day. During the fieldexercise, one soldier sought medical assistance to remove small " insects " crawling rapidly on his body. No specimens were reliably identified in the field or preserved for subsequent examination. No unusual illnesses were reported to medical personnel during the training exercise. After the field-training exercises, the soldiers spent 2 days in Gaborone, the capital of Botswana. Within 2 days of their return to their home station, approximately 30% of the deployed soldiers sought medical attention with symptoms of fever, headache, and regional lymphadenitis. Several soldiers reported insect bites. An epidemiologic team from Walter Reed Army Institute of Research was sent to Botswana to assist with the outbreak investigation. From airplane manifests, 169 soldiers were identified as having been deployed to Botswana. One week after the soldiers returned to their home station , a questionnaire requesting information on symptoms, personal protective measures taken against arthropod vectors, reservoir exposures, and other potential risk factors for infection was administered to all available soldiers (n = 140); 132 soldiers underwent directed physical examinations, in which skin lesions, lymphadenopathy, and right upper quadrant tenderness were noted. Clothing and equipment used in the field that had not been cleaned since the exercise were visually examined in detail by a team of entomologists. Blood samples from 126 soldiers were obtained at 1 week and 10 weeks postdeployment. Serum specimens were divided into aliquots and frozen at-20°C for laboratory analyses. Sera were tested for antibodies to rickettsiae by using an indirect fluorescence antibody technique (IFA) (2). Sera drawn at 10 weeks postdeployment were initially screened for whole immunoglobulin …