Validation of genetic and phenotypic markers and the difference between the sexes on nematode infection in Scottish blackface lambs

Abuargob, Omry Milad (2005) Validation of genetic and phenotypic markers and the difference between the sexes on nematode infection in Scottish blackface lambs. PhD thesis, University of Glasgow.

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Abstract

Sheep farming plays an important role in the economies in many countries, and is considered an important source of meat, milk, and wool for humans. Livestock are threatened by gastrointestinal parasites, especially nematode infection, which are one of the greatest causes of disease and lost productivity. Nematodes are traditionally controlled by anthelmintic compounds, but with reports of complete multi-drug resistance, other modalities of prevention and treatment are urgently needed. One of the additional methods for controlling nematode infection in domestic sheep is deliberate selection for parasite resistance. Hence, this thesis has investigated, firstly, the general distribution of faecal egg counts among and between Scottish Blackface lamb populations, which provides a better understanding of host parasite relationship. Secondly, it has identified the genetic markers that have significant association with resistance to nematode infection. This provides more through understanding of the genetic mechanism underlying nematode resistance. These results facilitate the selection of resistant animals. A longitudinal study of the mean and distribution of faecal egg counts was made in Scottish Blackface lambs following natural infection with gastrointestinal nematodes over three years at monthly intervals between August to October. This study has shown that there was no discernible pattern to faecal egg counts within each year and mean faecal egg counts in October were lower than mean faecal egg counts in September in each year, in addition faecal egg counts in male lambs were consistently higher than female lambs at 6-months of age. Mean egg counts vary among different populations and among the same population sampled at different time, and high means are not necessarily due to high intensities of infection but probably due to the contribution of species other than T. circumcincta. Older lambs showed significant association between faecal egg counts and polymorphisms in the IFN-gamma gene. Two genotypes at this microsatellite appear to be responsible for moderate and high faecal egg output, while the other genotype was associated with low faecal egg counts. Older male lambs showed significant association with the IFN-gamma loci, while female lambs did not.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Michael Stear
Keywords: Animal diseases, Veterinary science, Parasitology
Date of Award: 2005
Depositing User: Enlighten Team
Unique ID: glathesis:2005-71106
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 May 2019 10:49
Last Modified: 10 May 2019 10:49
URI: http://theses.gla.ac.uk/id/eprint/71106

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