Epidemiology of heartwater disease in West Africa: similar infection rate of Ehrlichia ruminantium evidenced in adults of Amblyomma variegatum and Rhipicephalus microplus in peri-urban villages of Bobo-Dioulasso, Burkina Faso

Abstract

Heartwater disease, is a virulent tick-borne disease of ruminants caused by Ehrlichia ruminantium (ER), biologically transmitted by Amblyomma spp. However, in West Africa, the potential of Rhipicephalus microplus (R. microplus) larvae to transmit this bacterium has been demonstrated. Although previous studies have been conducted on heartwater and ER in Burkina Faso, data on infection rate of the bacterium in A. variegatum and R. microplus is lacking in the peri-urban areas. Hence, this study aimed to compensate this gap, focusing on five peri-urban villages around 10-30 km from Bobo-Dioulasso. A total of 359 cattle was examined for ticks collection. However, only adult specimens of the two tick species collected on the same animals were included in the molecular detection of ER by semi-nested PCR. Results revealed a global contact rate of 19% in A. variegatum and 26% in R. microplus without a significant difference between these rates. Thus, while R. microplus invasion in West Africa is accompanied by the transmission of ER to animals, its contact rate with the causal agent of heartwater disease is similar to that with the previous known vector. Such context could impact the heartwater disease epidemiology, mainly in the peri-urban areas where the study was carried out. From previous knowledge and literature, that is the first time such study focusing on E. ruminantium infection rate in ticks in peri-urban areas is conducted. Results suggest the necessity to improve tick control methods in the study areas since both ticks species can transmit the causal agent of heartwater disease to animals.