Quantitative trait loci associated with parasitic infection in Scottish blackface sheep

Abstract

This study aimed to identify quantitative trait loci associated with endoparasitic infection in Scottish Blackface sheep. Data were collected from 789 animals over a 3-year period. All of the animals were continually exposed to a mixed nematode infection by grazing. Faecal samples were collected in August, September and October each year at ca. 16, 20 and 24 weeks of age; Nematodirus spp. eggs were counted separately from the other species of nematodes. Blood samples were collected in October from which immunoglobulin A (IgA) activity was measured and DNA was extracted for genotyping. In total, 139 Microsatellite markers were genotyped across eight chromosomal regions (chromosomes 1, 2, 3, 5, 14, 18, 20 and 21) in the sires and progeny were genotyped for the markers that were polymorphic in their sire. Evidence was found for quantitative trait loci (QTL) on chromosomes 2, 3, 14 and 20. QTL associated with specific IgA activity were identified in chromosomes 3 and 20, in regions close to IFNG (chromosome 3) and the MHC (chromosome 20). QTL associated with Nematodirus FEC were identified on chromosomes 2, 3 and 14. Lastly, QTL associated with non-Nematodirus Strongyle FEC were identified on chromosomes 3 and 20. This study has shown that some aspects of host resistance to gastrointestinal parasites are under strong genetic control, therefore these QTL could be utilised in a marker-assisted selection scheme to increase host resistance to gastrointestinal parasites.

Confirmation of two quantitative trait loci regions for nematode resistance in commercial British terminal sire breeds

“…*Denotes the 5% region-wide significance level. (Bishop et al, 2004;Davies et al, 2006;Salle G. and Bishop SC, 2007 unpublished results), although both types of FEC are heritable. Reported genetic correlations between Nematodirus and Strongyles FEC are invariably positive and moderate to strong, ranging from 0.49 to 0.93, across a range of environments and breeds (Bishop et al, 2004;Morris et al, 2004;Wolf et al, 2008).…”

“…Genotyping was done using multiplex microsatellite panels developed around the regions identified in the previous studies on OAR3 and OAR14 in Blackface sheep (Davies et al, 2006). This comprised a panel of seven microsatellite markers (KD103, BL4, IFNG, MAF23, CSRD111, BM6433 and BM8230) around the distal end of OAR3 and five microsatellite markers on OAR14 (INRA63, CSAP27, CSRD63, LSCV30 and BM6507).…”

“…Furthermore, these regions contain plausible candidate genes, namely, interferon-g (IFNG) and possibly genes located in the major histocompatibility complex, respectively. The region on OAR14 has only been observed in Blackface sheep (Davies et al, 2006), although another OAR14 FEC QTL was reported in Spanish milk sheep (Gutierrez-Gil et al, 2009). The region described by Davies et al (2006) contains interferon regulatory factor (IRF3), a toll-like receptor (TLR)-related gene.…”

“…The region on OAR14 has only been observed in Blackface sheep (Davies et al, 2006), although another OAR14 FEC QTL was reported in Spanish milk sheep (Gutierrez-Gil et al, 2009). The region described by Davies et al (2006) contains interferon regulatory factor (IRF3), a toll-like receptor (TLR)-related gene. As reported by Jann et al (2009), IRF3 is located in QTL regions affecting health traits in five species (human, mouse, pig, cattle and sheep) and, as such, is a plausible candidate gene for our QTL on OAR14.…”

“…Previous studies conducted at Roslin Institute (Davies et al, 2006), using Blackface sheep, identified regions of particular interest in ovine chromosomes (OAR) 3, 14 and 20. The regions on OAR3 and OAR20 are two of the few QTL for nematode resistance that are common across several studies (Buitkamp et al, 1999;Coltman et al, 2001;Charon et al, 2002; -E-mail: oswald.matika@roslin.ed.ac.uk Crawford et al, 2006;Beraldi et al, 2007).…”