Ehrlichia ruminantium infects Rhipicephalus microplus in West Africa

Abstract

Background: The variation of tick abundance on ruminants had received little attention in West Africa before Rhipicephalus (Boophilus) microplus started to invade this region in the early 2000s. Ten years later, R. microplus was suspected to have replaced the native ticks. In addition to testing this hypothesis, this study investigated the interactions between native and invasive ticks and the relative role of climatic and geographical variables in the variations of tick community composition (beta diversity) on cattle herds. Methods: A one-year-long survey was performed in Benin and Burkina Faso during which adult ticks were collected from 144 steers from 12 localities in four different areas once a month. Morphological features were used to assign the collected ticks to different species ( A. variegatum , R. annulatus, R. decoloratus, R. microplus and R. geigyi) . Beta diversity analyses and generalized linear models allowed characterizing the geographical variations in species assemblage and the effect of co-infestation patterns on the seasonal variations in the abundance and incidence rates of each taxon. Results: About 68 % (22,491/32,148) of all the adult ticks collected in one year were R. microplus . The most heterogeneously distributed taxa were Hyalomma spp and R. microplus and the lowest specific diversity was found in Central Burkina Faso. Although climatic variables did not provide any additional information on the variation in species assemblages compared with the sampling geography, adult tick abundance tended to peak during the late ( Boophilus subgenus) or early (other taxa) rainy season. In most taxon-per-locality analyses, the abundance and incidence rate of a given tick taxon significantly increased when the host was co-infested by other taxa. The comparison with previous estimates (when possible) did not support the hypothesis that R. microplus invasion led to a decrease in native tick species abundance. Conclusions: The co-infestation patterns among native and invasive tick species are key factors for the determination of the community structure and the infestation dynamics of each tick taxon in West African cattle.