Ehrlichia ruminantium infects Rhipicephalus microplus in West Africa

Abstract

BackgroundThe 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.MethodsEhrlichia 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.ResultsThe 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.ConclusionAccording 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1651-x) contains supplementary material, which is available to authorized users.

Cattle ticks and associated tick-borne pathogens in Burkina Faso and Benin: Apparent northern spread of Rhipicephalus microplus in Benin and first evidence of Theileria velifera and Theileria annulata

“…Some pools of A. variegatum were found positive to Ehrlichia ruminantium. This result was also expected as the presence of this pathogen is well known in the region (Adakal et al, 2010;Farougou et al, 2012;Biguezoton et al, 2016b;Adjou Moumouni et al, 2018) sometimes with high prevalence.…”

How relevant are in vitro culture models for study of tick-pathogen interactions?

“…However, the heightened susceptibility to the bacteria of ISE6 cells upon silencing other genes such as caspar was not observed in live ticks, in which infection was rather reduced. Therefore, while care should be taken when extrapolating in vitro results to the in vivo situation, sometimes an in vitro result, however unlikely, may be subsequently validated in vivo, as seen with cultivation of E. ruminantium in R. microplus cells [42] and the recent demonstration of transovarial transmission of the bacterium in R. microplus field ticks in West Africa [203].…”

Rhipicephalus microplusand its vector-borne haemoparasites in Guinea: further species expansion in West Africa

“…The rapid spread of R. microplus in West Africa entails a negative impact on the livestock sector. Heavy infestation of cattle with this tick causes weight loss, reduced milk production and increased cow mortality (Corrier et al 1979;Guerrero et al 2007 (Guerrero et al 2007;Biguezoton et al 2016).…”

“…Heavy infestation of cattle with this tick causes weight loss, reduced milk production and increased cow mortality (Corrier et al 1979; Guerrero et al 2007; Madder et al 2011; Rocha et al 2011; da Silva et al 2013). Furthermore, R. microplus causes considerable losses in cattle as a vector of several pathogens, including Babesia bigemina , Babesia bovis, Anaplasma marginale , and Ehrlichia ruminantium (Guerrero et al 2007; Biguezoton et al 2016).…”