A LONGITUDINAL SURVEY OF BORRELIA-CROCIDURAE PREVALENCE IN RODENTS AND INSECTIVORES IN SENEGAL

We report results of a longitudinal survey designed to determine the i mportance and the dynamics of Borrelia crocidurae, the spirochete resp onsible for tick-borne relapsing fever in West Africa in rodents and i nsectivores in a rural area of northern Senegal. A total of 954 animal s were caught during bimonthly capture sessions over a two-year period . Positive thick blood smears were recorded in 17.6% of the 740 rodent s and 7.3% of the 55 musk shrews tested. Variations of prevalence were analyzed in Arvicanthis niloticus and Mastomys huberti, which represe nted 62.7% and 28.3%, respectively, of the animals captured, and 65.7% and 27.6%, respectively, of the animals found infected. Borrelia croc idurae prevalence was significantly different between captures and flu ctuated separately for each species. Age-specific prevalence of B. cro cidurae showed distinct pat terns, decreasing with age from 50% in you nger juveniles to 3% in older adults for A. niloticus, while increasin g with age from 8% to 23% for M. huberti. No relationship was observed with animal abundance or with the season of the year for either speci es. These findings suggest that the diversity of the population dynami cs of host-vector-parasite associations in the Sahel region of Senegal may be a key factor for the relative stability of the borreliosis res ervoir.