Authors

Discussion

Background: Tick-borne diseases (TBDs) caused by bacteria, rickettsiae and protozoa impose a serious constraint to livestock health and production in sub-Saharan Africa (SSA) including Nigeria. Thus far, research focusing on TBDs in livestock from SSA in general and Nigeria, in particular, has majorly focused on large ruminants such as cattle with limited attention paid to small ruminants. In Nigeria, diagnosis of TBDs in livestock is essentially based on clinical signs, microscopic examination of blood smears and/or lymph node biopsies and serological methods for the detection of antibodies, with negligible use being made of sensitive molecular tools. The aim of this study was, therefore, to update the existing knowledge on the occurrence of TBDs-causing pathogens of veterinary and zoonotic importance in domestic ruminants from North-Western Nigeria,  focusing on the so far more neglected species of sheep.

Methods: In July 2016, 257 whole blood samples were collected from sheep in Kachia grazing reserve Kaduna State, North-Western Nigeria. Detection of TBD-causing microorganisms pathogens was conducted by means of PCR-based reverse line blotting (RLB) targeting a six genera of microorganisms including bacteria (i.e. Ehrlichia spp., Anaplasma spp., Rickettsia spp. and Bartonella spp.) and apicomplexan protozoa (Theileria spp. and Babesia spp.)

Results: 75.1 % (193/257) of sampled animals were found infected, with 21.7% (42/193) of them being positive for single infections and the great majority of them (78.2%, 151/193) being affected by multiple infections. Theileria equi-like was the most prevalent microorganism detected (66.3%), followed by Rickettsia spp. (20.2%), Anaplasma centrale (17.5%), Theileria velifera (12.1%), Theileria spp. (10.8%), Ehrlichia sp.Omatjenne (10.1%), Ehrlichia/Anaplasma spp. (10.1 %), Theileria mutans (8.9%), Theileria sp.MSD4 (5.8%), Bartonella spp. (3.1%), Babesia bovis (2.7%), Babesia spp.(1.25%), Babesia caballi (0.45%), Ehrlichia ruminantium (0.4%), and Rickettsia spp. of the “thypusgroup” (0.4%). Lambs were found significantly less infected than juvenile and adult sheep.

Conclusions: This survey ascertained the presence of haemoparasites of bacterial and parasitic (protozoal) aetiology, of veterinary and medical importance, in sheep from North-Central Nigeria. The rather high infection rates detected for several Theileria and Ehrlichia spp. and the broad diversity of pathogen species suggests their possible involvement in disease condition and serious production losses, especially when animals are subjected to stress (e.g. in case of drought and/or fodder shortages). The detection of several zoonotic agents (i.e. Rickettsia spp. and Bartonella spp.)  warrants further characterization studies to better assess risk for human infections in the area. On the whole, this study contributes to a better understanding of the prevalence and epidemiology of TBDs in Nigerian livestock. Based on this finding, possible control approaches, suited for the study area, will be discussed.