Tick-borne tularemia. An outbreak of lymphadenopathy in children.

Between June 1 and July 15, 1984, twenty persons with glandular tularemia were identified on the Lower Brule and Crow Creek Indian reservations in South Dakota. The median age of the patients was 6 years (range, 2 to 20 years). The clinical illness was mild, consisting of fever, headache, and lymphadenopathy. All lymphadenopathy was in the head and neck area. Dermacentor variabilis ticks were identified as the vector. Although the mild clinical illness suggested Francisella tularensis, type B, was the agent, both type A and type B strains of F tularensis were isolated from ticks collected from dogs in the area. Tularemia is generally thought to be a severe systemic illness in North America. This outbreak illustrates that it can be a mild disease and that both type A and type B strains can be tick-borne and coexist in the same ecosystem.