The epidemiology of tick-borne haemoparasites as determined by the reverse line blot hybridization assay in an intensively studied cohort of calves in western Kenya

Abstract

The development of sensitive surveillance technologies using PCR-based detection ofmicrobial DNA, such as the reverse line blot assay, can facilitate the gathering of epidemi-ological information on tick-borne diseases, which continue to hamper the productivityof livestock in many parts of Africa and elsewhere. We have employed a reverse line blotassay to detect the prevalence of tick-borne parasites in an intensively studied cohort ofindigenous calves in western Kenya. The calves were recruited close to birth and monitoredfor the presence of infectious disease for up to 51 weeks. The final visit samples from 453calves which survived for the study period were analyzed by RLB. The results indicated highprevalences of Theileria mutans (71.6%), T. velifera (62.8%), Anaplasma sp. Omatjenne (42.7%),A. bovis (39.9%), Theileria sp. (sable) (32.7%), T. parva (12.9%) and T. taurotragi (8.5%), withminor occurrences of eight other haemoparasites. The unexpectedly low prevalence of thepathogenic species Ehrlichia ruminantium was confirmed by a species-specific PCR targetingthe pCS20 gene region. Coinfection analyses of the seven most prevalent haemoparasitesindicated that they were present as coinfections in over 90% of the cases. The analysesrevealed significant associations between several of the Theileria parasites, in particular T.velifera with Theileria sp. sable and T. mutans, and T. parva with T. taurotragi. There was verylittle coinfection of the two most common Anaplasma species, although they were com-monly detected as coinfections with the Theileria parasites. The comparison of reverse line∗