The genetics of resistance and resilience to Haemonchus contortus infection in young merino sheep

Albers, G. A. A.; Gray, G. D.; Piper, L.R.; Barker, J. S. F.; Jambre, L.F. Le; Barger, I.A.

doi:10.1016/0020-7519(87)90103-2

Cited by 273 publications

(180 citation statements)

References 4 publications

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“…The heritability estimate for single FEC following artificial challenge with T. circumcincta (0.22) is similar in magnitude to those reported in sheep artificially challenged with H. contortus, which appear to be around 0.2 to 0.3 [1,24,37]. However, the present estimate seems to be lower than the heritabilities estimated for a single FEC following artificial challenge with T. colubriformis, which range from 0.3 to 0.6 [12,35,37].…”

Section: Discussionsupporting

confidence: 76%

A short-term divergent selection for resistance to Teladorsagia circumcincta in Romanov sheep using natural or artificial challenge

et al. 2004

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-This experiment was conducted to assess the efficiency of selection on the basis of response to artificial challenges in order to breed sheep resistant to natural infection. A shortterm divergent selection process was designed to estimate the genetic parameters of these two traits. Two flocks, including 100 Romanov ram lambs each, were challenged in 1990 when they were 6 months old. One flock received three artificial infections with 20 000 third-stage Teladorsagia circumcincta larvae, at intervals of 7 weeks. Faecal egg counts (FEC) were performed on Days 22, 25 and 28 post infection (p.i.) and the animals were drenched on Day 28 p.i. The other flock was grazed for 5 months on a pasture contaminated with the same species. Faecal samples were taken from the lambs at similar ages. About 5 rams with the lowest FEC and 5 with the highest FEC were selected in each flock and mated with unselected ewes. Their offspring (200 animals) were challenged in 1992, half in the same way as their sires, and the other half by the other method. Because of a drought in the summer of 1990, it was necessary to repeat part of the experiment, and in 1992 the 5 and 8 rams with the lowest and highest FEC, respectively, were selected from the offspring challenged on the pasture in 1992 and were mated with unselected ewes. Their progeny (about 80 animals) were challenged in 1994, half by natural infection, half by artificial infection. The mean FEC of the flock increased from the first to the third artificial infection. The natural infection was highly variable in different years, reflecting the difficulty of assessing resistance using this mode of challenge. Genetic parameters were estimated using animal models and REML solutions. The repeatabilities of the FEC following * Corresponding author: gruner@tours.inra.fr * * Present address: 28 rue du Couvent, L-1363 Howald, Luxembourg * * * Present address: Inra, Unité de recherches zootechniques, 97170 Petit-Bourg, French West Indies 218 L. Gruner et al.artificial and natural infection were 0.49 and 0.70 respectively within a period of one week, and 0.22 and 0.41 respectively for periods separated by intervals of 7 weeks; the heritabilities of the single egg count were 0.22 and 0.38 respectively. The genetic correlation was 0.87: the FEC recorded under natural or artificial infection appear to depend on the same genetic potential.host resistance / sheep-nematoda / Teladorsagia circumcincta / genetic parameters

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Section: Discussionsupporting

confidence: 76%

A short-term divergent selection for resistance to Teladorsagia circumcincta in Romanov sheep using natural or artificial challenge

et al. 2004

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“…The method can be potentially applied also in sheep-breeding programmes, in which the degree of intestinal nematode infection is recorded from faecal worm-egg counts. This can be done under natural infections or after experimentally infecting animals in the field (Albers et al, 1987;Woolaston & Windon, 2001).…”

Section: (I) Random Regression Modelsmentioning

confidence: 99%

“…Tolerance is defined as the ability of the host to limit the impact of a given pathogen burden on host health, performance and ultimately on fitness (Painter, 1958 ;Simms & Triplett, 1994). In farm animal science, tolerance is sometimes termed resilience (Clunies-Ross, 1932;Albers et al, 1987 ;Bisset & Morris, 1996). Resistance and tolerance together define a host's defensive capacity, yet they have very different influences on hostxpathogen interactions.…”

Section: Introductionmentioning

confidence: 99%

Genetic analysis of tolerance to infections using random regressions: a simulation study

Kause

2011

Genet. Res.

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SummaryTolerance to infections is the ability of a host to limit the impact of a given pathogen burden on host performance. This simulation study demonstrated the merit of using random regressions to estimate unbiased genetic variances for tolerance slope and its genetic correlations with other traits, which could not be obtained using the previously implemented statistical methods. Genetic variance in tolerance was estimated as genetic variance in regression slopes of host performance along an increasing pathogen burden level. Random regressions combined with covariance functions allowed genetic variance for host performance to be estimated at any point along the pathogen burden trajectory, providing a novel means to analyse infection-induced changes in genetic variation of host performance. Yet, the results implied that decreasing family size as well as a non-zero environmental or genetic correlation between initial host performance before infection and pathogen burden led to biased estimates for tolerance genetic variance. In both cases, genetic correlation between tolerance slope and host performance in a pathogen-free environment became artificially negative, implying a genetic trade-off when it did not exist. Moreover, recording a normally distributed pathogen burden as a threshold trait is not a realistic way of obtaining unbiased estimates for tolerance genetic variance. The results show that random regressions are suitable for the genetic analysis of tolerance, given suitable data structure collected either under field or experimental conditions.

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“…As a second direct measure of the host's ability to suppress establishment and/or subsequent development of infection (Albers et al 1987) we used total worm burden. While larvae recovered from the small intestine in the present study had completed migration, they were still vulnerable to expulsion, i.e.…”

Section: _txnip_ds0871281_2_2 (Txnip)mentioning

confidence: 99%

Functional study of a genetic marker allele associated with resistance toAscaris suumin pigs

et al. 2014

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SUMMARYTwo single nucleotide polymorphisms (SNP TXNIP and SNP ARNT), both on chromosome 4, have been reported to be associated with roundworm (Ascaris suum) burden in pigs. In the present study, we selected pigs with two SNP TXNIP genotypes (AA; n = 24 and AB; n = 24), trickle-infected them with A. suum from 8 weeks of age until necropsy 8 weeks later, and tested the hypothesis that pigs with the AA genotype would have higher levels of resistance than pigs of AB genotype. We used different indicators of resistance (worm burden, fecal egg counts (FEC), number of liver white spots and A. suum-specific serum IgG antibody levels). Pigs of the AA genotype had lower mean macroscopic worm burden (2·4 vs 19·3; P = 0·06), lower mean total worm burden (26·5 vs 70·1; P = 0·09) and excreted fewer A. suum eggs at week 8 PI (mean number of eggs/g feces: 238 vs 1259; P = 0·14) than pigs of the AB genotype, as expected based on prior associations. The pigs were also genotyped at another locus (SNP ARNT) which showed a similar trend. This study provides suggestive evidence that resistant pigs may be selected using a genetic marker, TXNIP, and provides further support to the quantitative trait locus on chromosome 4.

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The genetics of resistance and resilience to Haemonchus contortus infection in young merino sheep

Cited by 273 publications

References 4 publications

A short-term divergent selection for resistance to Teladorsagia circumcincta in Romanov sheep using natural or artificial challenge

A short-term divergent selection for resistance to Teladorsagia circumcincta in Romanov sheep using natural or artificial challenge

Genetic analysis of tolerance to infections using random regressions: a simulation study

Functional study of a genetic marker allele associated with resistance toAscaris suumin pigs

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