Exploring the ecologies of campylobacter and eimeria infections in UK sheep
Several gastrointestinal parasites of sheep have veterinary and zoonotic importance, includingcoccidia belonging to the genus Eimeria and proteobacteria belonging to the genusCampylobacter. In the UK, both Eimeria and Campylobacter are both frequently isolated fromsheep faeces, and studies have shown that infections or co-infections by 10 or more Eimeriaspecies may occur. Campylobacter jejuni and Campylobacter coli are the most frequently encountered sheepassociatedCampylobacter species. Despite their potential veterinary and public healthimportance, little work has been reported to date exploring the ecologies of thesemicroorganisms. This project addressed this shortfall by completing cross-sectional and longitudinal surveys ofEimeria and Campylobacter infections in sheep flocks in southern Cumbria. In total almost1000 ovine faecal samples were collected on 27 visits to three farms in the region. Infectionswere diagnosed, and infecting species of both genera delineated, using well-establishedmethods. These results were collated with information about the timing of sample collectionand the age of sheep, and climate data. Significant seasonal trends in the epidemiology ofEimeria and Campylobacter infections were observed. Furthermore, the intensity of Eimeriainfections was also found to be significantly correlated with season, but, in addition with sheepage, rainfall prior to sample collection and, interestingly, to Campylobacter co-infection. Another strand of the study was to assess the role of wildlife as reservoirs for sheep-associatedcampylobacters. A survey of red and roe deer living in the vicinity of the three farms studiedfailed to implicate either species in this role, suggesting they do not contribute to the naturalpersistence of these bacteria in Cumbrian sheep populations. Finally, in an attempt to develop new molecular methods for the delineation of sheep-associatedEimeria species, next-generation sequencing (NGS) was used to try and attribute 18S rDNAsequences to Eimeria species present in multi-Eimeria species co-infections. In initial studies,18S rDNA libraries derived from mock communities of four chicken-associated Eimeriaspecies were analysed to assess how accurately NGS data matched the relative abundance ofeach Eimeria species, determined using traditional oocyst counting methods. Unfortunately, nosuggestion of a correlation was apparent. Overall the project clarified the epidemiology of two genera of significant sheep-associatedpathogens and was able to identify some important ecological determinants of thisepidemiology.
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