Molecular Detection of Ehrlichia ruminantium in Cattle From Different Agro-Ecological Zones of Cameroon: Implication for the Understanding of the Heartwater Epidemiology.

Although Amblyomma variegatum and Ehrlichia ruminantium infections have been reported in cattle from some agro-ecological zones (AEZs) of Cameroon, the transmission patterns of this bacterium seem to vary according to endemic areas and its prevalence as well as that of Heartwater remains not well understood in most sub-Saharan African countries. This study was designed to detect E. ruminantium infections in cattle of four AEZs of Cameroon and to identify areas presenting enzootic stability and those with potentially high risk for Heartwater. Blood samples were collected from cattle in four AEZs of Cameroon. DNA was extracted from blood and semi-nested PCR targeting the 16S rRNA gene of E. ruminantium was used to search for this bacterium. From 569 cattle analysed, an E. ruminantium DNA fragment was detected in 197 of them, giving an overall prevalence of 34.6%. The highest prevalence of E. ruminantium of 48.0% was recorded in cattle from AEZ IV and the lowest (26.0%) in those from AEZ III. Among the AEZs, significant differences (X = 14.85, p = 0.002) were recorded in terms of the prevalence of E. ruminantium infections. Villages of the westerly areas are at higher risk for E. ruminantium infections. This study revealed a high prevalence and a wide distribution of E. ruminantium infections in AEZs of Cameroon. It enabled the identification of areas showing an enzootic stability for E. ruminantium transmission as well as those where the transmission of this bacterium is low and where livestock are at higher risk of developing Heartwater.