title: No evidence for a universal association between variation in faecal egg count for a mixed field-challenge of gastrointestinal parasites and the presence of the Ovar-DQA1 null haplotype in sheep.
abstract: We tested the association of the Ovar-DQA1 null haplotype with faecal egg count (FEC) in 4676 male lambs sourced from 185 different sire-lines and four breeds. For each lamb a faecal sample was collected at weaning (approx. 4 months of age) and mid-autumn (approx. 9 months of age) and each was typed for the presence of Ovar-DQA1 null. General Linear Mixed Models (GLMMs) were used to analyse the relationship between FEC and Ovar-DQA1 null, both across and within breeds. Two models were used, the first testing the effect of the presence/absence of Ovar-DQA1 null and the second testing the effect of the number of copies of Ovar-DQA1 null present in an animal's genotype (i.e. dominant/recessive or additive effects). Across the breeds, no significant effect of the presence of Ovar-DQA1 null on FEC for Nematodirus sp., Strongyle genera, or total FEC was detected at either 4 or 9 months of age using either of the models. Within breeds, significant associations were detected at 4 months in South African Meat Merinos, with the presence of Ovar-DQA1 null in an animal's genotype being associated with a lower strongyle (absent: n=23, geometric mean=135epg; present: n=10, geometric mean=67epg; P=0.025) and total FEC (absent: n=23, geometric mean=220epg; present: n=10, geometric mean=121epg; P=0.017). These associations were not detected at 9 months of age.
authors.affiliation: Faculty of Health and Sport Sciences, Eastern Institute of Technology, Private Bag 1201, Napier, New Zealand.
authors.forename: R H J
authors.initials: RH
authors.lastname: Forrest
authors.forename: H
authors.initials: H
authors.lastname: Zhou
authors.forename: Q
authors.initials: Q
authors.lastname: Fang
authors.forename: A
authors.initials: A
authors.lastname: Smyth
authors.forename: C M
authors.initials: CM
authors.lastname: Frampton
authors.forename: J G H
authors.initials: JG
authors.lastname: Hickford
mesh_terms: D000818:Animals; D005243:Feces / Q000469:parasitology; D006239:Haplotypes; D008285:Major Histocompatibility Complex; D008297:Male; D010270:Parasite Egg Count / Q000662:veterinary*; D012756:Sheep / Q000235:genetics / Q000276:immunology* / Q000469:parasitology*; D013045:Species Specificity; D017183:Strongylida / Q000302:isolation & purification