Molecular detection of tick-borne pathogens in cattle from Southwestern Ethiopia.

Ard M. Nijhof,Maximilian Baumann,Zerihun Hailemariam,Jürgen Krücken,Peter-Henning Clausen,William Barendse,Jabbar S. Ahmed

doi:10.1371/journal.pone.0188248

Ard M. Nijhof, Maximilian Baumann + Show 5 more

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https://doi.org/10.1371/journal.pone.0188248

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Journal: PloS one	Publication Date: Nov 20, 2017
Citations: 64	License type: CC BY 4.0

Affiliation: Freie Universität Berlin, Haramaya University

Abstract

Tick-borne diseases (TBDs) cause significant losses among livestock and impact the livelihoods of resource-poor farming communities worldwide. In Ethiopia, detailed studies on the epidemiology of tick-borne pathogens (TBPs) in cattle using sensitive molecular detection methods are scarce. The objective of this study was to determine the prevalence and species composition of bovine TBPs of veterinary significance in local cattle populations. A comprehensive cross-sectional epidemiological study was conducted in cattle populations of Illubabor zone in Southwestern Ethiopia from June to August 2013. For this purpose, blood samples were collected from 392 cattle. A combination of polymerase chain reaction (PCR) and a Reverse Line Blot (RLB) hybridization assay was employed for the detection of TBPs in these samples. The PCR/RLB results of the 392 blood samples indicated a high overall prevalence of 96.9% for TBPs, including Theileria mutans (66.1%), Theileria orientalis (51.8%), Anaplasma sp. Omatjenne (25.5%), Anaplasma marginale (14.5%), Babesia bigemina (14.0%) and Theileria velifera (13.0%) and minor occurrences of Ehrlichia ruminantium (0.5%) and Ehrlichia minasensis (0.26%). Moreover, three novel Anaplasma genotypes were detected in bovine blood samples. A phylogenetic analysis revealed that they most likely represent three, but at least two, new species. The prevalence of the three novel Anaplasma species, preliminary designated as Anaplasma sp. Hadesa, Anaplasma sp. Saso and Anaplasma sp. Dedessa, was 12.5%, 14.3% and 5.6%, respectively. Overall, a total of 227 cattle (57.9%) were found to be co-infected with two or more TBPs simultaneously and 86 different species combinations were observed. The findings show a very high burden of infection of cattle with TBPs in Ethiopia. The high frequency of co-infections suggests that clinical manifestations might be complex. Further research is required to determine the pathogenicity, host cell types and vector of the three novel Anaplasma species identified in this study.

Highlights

With approximately 54 million heads of cattle, Ethiopia is considered to have the largest livestock population in Africa
This includes bovine babesiosis caused by Babesia bigemina and Babesia bovis, bovine anaplasmosis caused by Anaplasma marginale and heartwater caused by Ehrlichia ruminantium
A combination of polymerase chain reaction (PCR) and a Reverse Line Blot (RLB) hybridization assay was employed for the simultaneous detection of tick-borne pathogens (TBPs) from bovine blood samples collected on Flinders Technology Associates (FTA) cards

Summary

Introduction

With approximately 54 million heads of cattle, Ethiopia is considered to have the largest livestock population in Africa. In Ethiopia, cattle are infested by several species of hard ticks (Acari: Ixodidae) including Amblyomma cohaerens, Amblyomma variegatum, Rhipicephalus decoloratus, Rhipicephalus pulchellus, Rhipicephalus evertsi evertsi, Rhipicephalus praetextatus and Hyalomma rufipes [2]. These ticks can act as vectors for a variety of pathogens with veterinary and zoonotic importance and several tick-borne diseases (TBDs) are known to be endemic in Ethiopia. In indigenous breeds of cattle, the course of these TBDs is usually subclinical. They pose a greater challenge to susceptible exotic breeds of cattle, representing a major constraint in the upgrading and development of cattle production in Ethiopia [7]

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