Al-neama, RT
2017,
Exploring the ecologies of campylobacter and eimeria infections in UK sheep
, PhD thesis, University of Salford.
Abstract
Several gastrointestinal parasites of sheep have veterinary and zoonotic importance, including
coccidia belonging to the genus Eimeria and proteobacteria belonging to the genus
Campylobacter. In the UK, both Eimeria and Campylobacter are both frequently isolated from
sheep faeces, and studies have shown that infections or co-infections by 10 or more Eimeria
species may occur.
Campylobacter jejuni and Campylobacter coli are the most frequently encountered sheepassociated
Campylobacter species. Despite their potential veterinary and public health
importance, little work has been reported to date exploring the ecologies of these
microorganisms.
This project addressed this shortfall by completing cross-sectional and longitudinal surveys of
Eimeria and Campylobacter infections in sheep flocks in southern Cumbria. In total almost
1000 ovine faecal samples were collected on 27 visits to three farms in the region. Infections
were diagnosed, and infecting species of both genera delineated, using well-established
methods. These results were collated with information about the timing of sample collection
and the age of sheep, and climate data. Significant seasonal trends in the epidemiology of
Eimeria and Campylobacter infections were observed. Furthermore, the intensity of Eimeria
infections was also found to be significantly correlated with season, but, in addition with sheep
age, 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-associated
campylobacters. A survey of red and roe deer living in the vicinity of the three farms studied
failed to implicate either species in this role, suggesting they do not contribute to the natural
persistence of these bacteria in Cumbrian sheep populations.
Finally, in an attempt to develop new molecular methods for the delineation of sheep-associated
Eimeria species, next-generation sequencing (NGS) was used to try and attribute 18S rDNA
sequences to Eimeria species present in multi-Eimeria species co-infections. In initial studies,
18S rDNA libraries derived from mock communities of four chicken-associated Eimeria
species were analysed to assess how accurately NGS data matched the relative abundance of
each Eimeria species, determined using traditional oocyst counting methods. Unfortunately, no
suggestion of a correlation was apparent.
Overall the project clarified the epidemiology of two genera of significant sheep-associated
pathogens and was able to identify some important ecological determinants of this
epidemiology.
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