Influence of the Biotope on the Tick Infestation of Cattle and on the Tick-Borne Pathogen Repertoire of Cattle Ticks in Ethiopia

Abstract

BackgroundThe majority of vector-borne infections occur in the tropics, including Africa, but molecular eco-epidemiological studies are seldom reported from these regions. In particular, most previously published data on ticks in Ethiopia focus on species distribution, and only a few molecular studies on the occurrence of tick-borne pathogens or on ecological factors influencing these. The present study was undertaken to evaluate, if ticks collected from cattle in different Ethiopian biotopes harbour (had access to) different pathogens.MethodsIn South-Western Ethiopia 1032 hard ticks were removed from cattle grazing in three kinds of tick biotopes. DNA was individually extracted from one specimen of both sexes of each tick species per cattle. These samples were molecularly analysed for the presence of tick-borne pathogens.Results Amblyomma variegatum was significantly more abundant on mid highland, than on moist highland. Rhipicephalus decoloratus was absent from savannah lowland, where virtually only A. cohaerens was found. In the ticks Coxiella burnetii had the highest prevalence on savannah lowland. PCR positivity to Theileria spp. did not appear to depend on the biotope, but some genotypes were unique to certain tick species. Significantly more A. variegatum specimens were rickettsia-positive, than those of other tick species. The presence of rickettsiae (R. africae) appeared to be associated with mid highland in case of A. variegatum and A. cohaerens. The low level of haemoplasma positivity seemed to be equally distributed among the tick species, but was restricted to one biotope type.ConclusionsThe tick biotope, in which cattle are grazed, will influence not only the tick burden of these hosts, but also the spectrum of pathogens in their ticks. Thus, the presence of pathogens with alternative (non-tick-borne) transmission routes, with transstadial or with transovarial transmission by ticks appeared to be associated with the biotope type, with the tick species, or both, respectively.

Occurrence and Genotyping of Coxiella burnetii in Ixodid Ticks in Oromia, Ethiopia

“…A reliable molecular strategy was used that has been validated in recent studies, and our findings were confirmed by positive and negative controls and by amplification of several target genes as previously described. 12 The overall frequency of C. burnetii (6.4%; 54/842) in our study is lower than the overall prevalence of 10.8% (32/295) 35 in ticks along Didessa valley recently reported from Ethiopia. This difference is most probably attributed to factors like in our study a sample was considered positive when it was positive for recently developed two different types of genes (COX and IS30A spacers); however, the previous study used only one gene (IS1111 spacer).…”

“…The other possible factors are differences in the number of species and quantity of ticks tested, geographical locations and seasons of tick collections by the two studies might affect the prevalence. We have tested a total of 842 ticks consisting 13 different species from 9 districts in Oromia; however, the previous study 35 tested only 295 ticks comprising 7 species from one region along Didessa valley in southwest Ethiopia.…”

Molecular characterization of Theileria orientalis from cattle in Ethiopia

“…and Rhipicephalus sp. collected from cattle in western Oromia and south-western Oromia, along the Didessa valley, Ethiopia (Hornok et al, 2014;Kumsa et al, 2014). However, in the Asia-Pacific region, where the clinical form of oriental theileriosis is common, Haemaphysalis spp.…”

Identification of Novel Coxiella burnetii Genotypes from Ethiopian Ticks

“…A total of 296 ticks ( Amblyomma variegatum , n = 118; A. cohaerens , n = 100; A. lepidum , n = 2; Rhipicephalus decoloratus , n = 50; R. evertsi , n = 17; R. praetextatus , n = 8 and Hyalomma rufipes , n = 1) were collected from 109 cattle belonging to 18 different herds (zebu breed) in Didessa valley, south-western Ethiopia (09°05′N, 36°33′E - 7°40′N, 36°50E) in 2012 ( Figure 1 ) [11] . Because sampling was part of the regular veterinary care and the field studies did not involve endangered or protected species, no specific permissions were required for these activities.…”

“…determine the cycle threshold (Ct) values), all tick samples were analyzed by a TaqMan based real-time PCR assay targeting the multi-copy IS 1111 insertion element of C. burnetii genome [13] . From the 32 positive samples, 8 cases ( Amblyomma cohaerens , n = 6; A. variegatum , n = 2) which harbored sufficient amount of C. burnetii DNA (Ct<35) were selected for genotyping [11] .…”