Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519793
Title: Host reactions to coccidia in the sheep and rabbit and their relevance to intestinal disease
Author: Gregory, M. W.
Awarding Body: Royal Veterinary College (University of London)
Current Institution: Royal Veterinary College (University of London)
Date of Award: 1984
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Abstract:
Intestinal disease is an important cause of economic loss in the sheep and rabbit industries, and the part played by coccidia is difficult to define. This study was to improve our understanding of how coccidia cause disease, how this disease can be diagnosed and how immunity to it is acquired. Infections with known numbers of known coccidial species were given to coccidia-free lambs and rabbits. Clinical (and in some cases haematological) data and oocyst output were recorded. Animals were killed at different intervals after infection, and their tissues examined by light microscopy and by transmission scanning electron microscopy. Studies were also made in field lambs on active and passive immunity and on oocyst output in relation to clinical signs. Eimevia flavescens in rabbits and E. ovinoidalis in lambs are reputed to be highly pathogenic. They were found to share some features of their life-cycle not shared by less harmful species. Gametocytes were the most harmful stage; these infected cells of the caecal crypts, including stem cells at the crypt bases. If large numbers of gametocytes were involved, crypt cells were eliminated over large areas of caecum, leaving the mucosa denuded and depleted of regenerative capacity. Less pathogenic species such as E. irresidua in rabbits and E. ovina in lambs appeared to favour the superficial epithalial cells leaving the crypt cells to restore the epithelial covering rapidly after the coccidia had passed. Z. ovina appeared sometimes to stimulate proliferation of host enterocytes, causing polyp formation. The susceptibility of lambs appeared to be modified by both active and passive immunity. Tine factors appeared to interact in a complex way with each other arid with incoming coccidia, which suggested a need for much further research. Oocyst output was of little value as an indicator of the tiptake of coccidia or of the part played by them in the aetiology of intestinal disease.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.519793  DOI: Not available
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