Ehrlichia ruminantium infects Rhipicephalus microplus in West Africa

Background The invasion of West Africa by Rhipicephalus microplus during the past decade has changed the ecological situation of the agent of heartwater Ehrlichia ruminantium in this area. Before, its local vector, Amblyomma variegatum, was the most abundant tick species found on livestock. Today, the abundance of the R. microplus is one magnitude higher than that of A. variegatum in many west-African localities. We investigated the potential of this new ecological situation to impact the circulation of E. ruminantium in West Africa. Methods Ehrlichia ruminantium infections were assessed with the specific PCR-diagnosis targeting the PCS20 region. This screening was applied on field samples of 24 R. microplus adults, on four females from a laboratory strain that had been blood-fed since larvae on one E. ruminantium -infected steer as well as on the offspring of these females at egg and larval stages. Results The PCR detected E. ruminantium in 29 % of the field-collected R. microplus , i.e. twice as much as reported for A. variegatum with the same protocol. Regarding the laboratory strain, the PCR-diagnosis performed showed that all females were infected and passed the rickettsia to their progeny. Sequencing of the PCR product confirmed that the maternally inherited rickettsia was E. ruminantium . Conclusion According to the present findings, the invasive dynamic of R. microplus in West Africa is currently impacting the local evolutionary conditions of E. ruminantium since it offers new transmission roads such as maternal transmission in R. microplus .