title: Association between variation in faecal egg count for a natural mixed field-challenge of nematode parasites and TLR4 variation.
abstract: Research has shown that Toll-like receptor 4 (TLR4) is important in immune responses to some helminth parasites. In sheep, variation in the PAMP region of TLR4 may result in structurally and thus functionally different TLR4 molecules, and this may consequently lead to variation in the TLR4 response to parasite infections. This study involved three separate, but related sheep breeds (Merino, Polwarth and Corriedale sheep) and a total of 885 lambs from five New Zealand farms that underwent a mixed field-challenge from gastro-intestinal parasites. Faecal samples were collected at approximately 4 and 9 months of age and faecal egg counts (FECs) for Nematodirus spp. and Strongyle species determined, along with the total number of eggs per gram (EPG). Analysis of the five farms collectively revealed an association (P=0.023) between the presence of TLR4 variant *02 (mean 24 EPG) and the absence of the variant (mean 32 EPG) at 9 months of age. Conversely the presence of *03 had a significantly (P=0.047) higher mean Nematodirus spp. FEC (mean 42 EPG) compared to the absence (mean 28 EPG) at 9 months of age. More associations were revealed when the data were split according to the dominant faecal parasite species. With a predominantly Trichostrongylus spp. FEC group of lambs at 9 months of age, the presence of TLR4 variant *02 was found to have significantly (P=0.003) lower Nematodirus spp. FEC (mean 4 EPG), and also significantly (P=0.033) lower total FEC (mean 312 EPG) when compared to sheep without the variant (mean 15 EPG and 449 EPG, respectively). The presence of TLR4 variant *03 and *04 were associated or tended to be associated (P=0.010 and P=0.088, respectively) with higher Nematodirus spp. FEC (mean 25 EPG and 22 EPG, respectively) when compared to lambs without the variant (mean 10 EPG and 11 EPG, respectively). These results suggest that TLR4 variation may be affecting the immune response to gastro-intestinal parasites in sheep, although principally to Nematodirus spp. infections and not Strongyle species infections.
authors.affiliation: Gene-Marker Laboratory, Department of Agricultural Sciences, Faculty of Agriculture and Life Sciences, PO Box 85084, Lincoln University, Lincoln 7647, Christchurch, New Zealand.
authors.forename: Y-S
authors.initials: YS
authors.lastname: Lin
authors.affiliation: Gene-Marker Laboratory, Department of Agricultural Sciences, Faculty of Agriculture and Life Sciences, PO Box 85084, Lincoln University, Lincoln 7647, Christchurch, New Zealand.
authors.forename: H
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Faculty of Health and Sport Sciences, Eastern Institute of Technology, Private Bag 1201, Napier 4142, New Zealand.
authors.forename: R H J
authors.initials: RH
authors.lastname: Forrest
authors.affiliation: Christchurch School of Medicine and Health Sciences, PO Box 4345, Christchurch, New Zealand.
authors.forename: C M
authors.initials: CM
authors.lastname: Frampton
authors.affiliation: Gene-Marker Laboratory, Department of Agricultural Sciences, Faculty of Agriculture and Life Sciences, PO Box 85084, Lincoln University, Lincoln 7647, Christchurch, New Zealand.
authors.forename: L E R
authors.initials: LE
authors.lastname: Burrows
authors.affiliation: Gene-Marker Laboratory, Department of Agricultural Sciences, Faculty of Agriculture and Life Sciences, PO Box 85084, Lincoln University, Lincoln 7647, Christchurch, New Zealand. Electronic address: hickford@lincoln.ac.nz.
authors.forename: J G H
authors.initials: JG
authors.lastname: Hickford
mesh_terms: D000818:Animals; D001947:Breeding; D005243:Feces / Q000469:parasitology; D008297:Male; D009349:Nematode Infections / Q000235:genetics / Q000276:immunology / Q000662:veterinary*; D009520:New Zealand; D010270:Parasite Egg Count; D016133:Polymerase Chain Reaction; D018807:Polymorphism, Single-Stranded Conformational; D012756:Sheep; D012757:Sheep Diseases / Q000235:genetics* / Q000469:parasitology*; D051197:Toll-Like Receptor 4 / Q000235:genetics*
chemical_list: D051197:Toll-Like Receptor 4
keywords: Faecal egg count (FEC); Gastrointestinal parasites; Sheep; TLR4; Variation