Genetic variation in parasite resistance of Atlantic salmon to amoebic gill disease over multiple infections

Kube, Peter; Taylor, Richard; Elliott, Nicholas

doi:10.1016/j.aquaculture.2012.08.026

Cited by 58 publications

(44 citation statements)

References 26 publications

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“…These include viral infectivity of fin explants, or fibroblastic cell lines from cloned trout, that correlate with the susceptibility of either the progeny or the adult fish stocks to viral haemorrhagic septicaemia virus [50], [51]. In Atlantic salmon, gill lesion score is correlated with survival results following experimental amoebic gill disease challenge or natural infection [52], [53]. At present, we have not identified a mechanistic connection between spleen size and BCWD resistance.…”

Section: Discussionmentioning

confidence: 75%

Assessment of Genetic Correlation between Bacterial Cold Water Disease Resistance and Spleen Index in a Domesticated Population of Rainbow Trout: Identification of QTL on Chromosome Omy19

et al. 2013

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Selective breeding of animals for increased disease resistance is an effective strategy to reduce mortality in aquaculture. However, implementation of selective breeding programs is limited by an incomplete understanding of host resistance traits. We previously reported results of a rainbow trout selection program that demonstrated increased survival following challenge with Flavobacterium psychrophilum, the causative agent of bacterial cold water disease (BCWD). Mechanistic study of disease resistance identified a positive phenotypic correlation between post-challenge survival and spleen somatic-index (SI). Herein, we investigated the hypothesis of a genetic correlation between the two traits influenced by colocalizing QTL. We evaluated the inheritance and calculated the genetic correlation in five year-classes of odd- and even-year breeding lines. A total of 322 pedigreed families (n = 25,369 fish) were measured for disease resistance, and 251 families (n = 5,645 fish) were evaluated for SI. Spleen index was moderately heritable in both even-year (h2 = 0.56±0.18) and odd-year (h2 = 0.60±0.15) lines. A significant genetic correlation between SI and BCWD resistance was observed in the even-year line (rg = 0.45±0.20, P = 0.03) but not in the odd-year line (rg = 0.16±0.12, P = 0.19). Complex segregation analyses of the even-year line provided evidence of genes with major effect on SI, and a genome scan of a single family, 2008132, detected three significant QTL on chromosomes Omy19, 16 and 5, in addition to ten suggestive QTL. A separate chromosome scan for disease resistance in family 2008132 identified a significant BCWD QTL on Omy19 that was associated with time to death and percent survival. In family 2008132, Omy19 microsatellite alleles that associated with higher disease resistance also associated with increased spleen size raising the hypothesis that closely linked QTL contribute to the correlation between these traits. To our knowledge, this is the first estimation of spleen size heritability and evidence for genetic linkage with specific disease resistance in a teleost fish.

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Section: Discussionmentioning

confidence: 75%

Assessment of Genetic Correlation between Bacterial Cold Water Disease Resistance and Spleen Index in a Domesticated Population of Rainbow Trout: Identification of QTL on Chromosome Omy19

et al. 2013

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“…Studies indicating higher heritability values of resistance (i.e. greater than 20%) have generally been conducted in experimental settings [47,48] whereby non-transmitted factors were controlled for. It is hence likely that our relatively low values of heritability are inherent to the natural settings in which we performed our investigation.…”

Section: Discussionmentioning

confidence: 99%

Heritable variation in host tolerance and resistance inferred from a wild host–parasite system

et al. 2014

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Hosts have evolved two distinct defence strategies against parasites: resistance (which prevents infection or limit parasite growth) and tolerance (which alleviates the fitness consequences of infection). However, heritable variation in resistance and tolerance and the genetic correlation between these two traits have rarely been characterized in wild host populations. Here, we estimate these parameters for both traits in Leuciscus burdigalensis, a freshwater fish parasitized by Tracheliastes polycolpus. We used a genetic database to construct a full-sib pedigree in a wild L. burdigalensis population. We then used univariate animal models to estimate inclusive heritability (i.e. all forms of genetic and non-genetic inheritance) in resistance and tolerance. Finally, we assessed the genetic correlation between these two traits using a bivariate animal model. We found significant heritability for resistance (H ¼ 17.6%; 95% CI: 7.2-32.2%) and tolerance (H ¼ 18.8%; 95% CI: 4.4-36.1%), whereas we found no evidence for the existence of a genetic correlation between these traits. Furthermore, we confirm that resistance and tolerance are strongly affected by environmental effects. Our results demonstrate that (i) heritable variation exists for parasite resistance and tolerance in wild host populations, and (ii) these traits can evolve independently in populations.

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“…This clearly indicates the usefulness of this non-destructive molecular diagnostic assay for the early detection of N. perurans and in subclinical cases of AGD. Additionally, with significant gains made through selective breeding (as measured by reduced gill score, Kube et al, 2012) there is an opportunity to fully optimize nondestructive sampling techniques in conjunction with molecular methods to help inform management decisions, such as when to treat fish and also determine the efficacy of treatments, and to more finely measure potential gains in AGD resistance/ resilience. …”

Section: Discussionmentioning

confidence: 99%

Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

et al. 2017

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Amoebic gill disease (AGD) caused by Neoparamoeba perurans, has emerged in Europe as a significant problem for the Atlantic salmon farming industry. Gross gill score is the most widely used and practical method for determining AGD severity on farms and informing management decisions on disease mitigation strategies. As molecular diagnosis of AGD remains a high priority for much of the international salmon farming industry, there is a need to evaluate the suitability of currently available molecular assays in conjunction with the most appropriate non-destructive sampling methodology. The aims of this study were to assess a non-destructive sampling methodology (gill swabs) and to compare a range of currently available real-time polymerase chain-reaction (PCR) assays for the detection of N. perurans. Furthermore a comparison of the nondestructive molecular diagnostics with traditional screening methods of gill scoring and histopathology was also undertaken. The study found that all molecular protocols assessed performed well in cases of clinical AGD with high gill scores. A TaqMan based assay (protocol 1) was the optimal assay based on a range of parameters including % positive samples from a field trial performed on fish with gill scores ranging from 0 to 5. A higher proportion of gill swab samples tested positive by all protocols than gill filament biopsies and there was a strong correlation between gill swabs tested by protocol 1 and gross gill score and histology scores. Screening for N. perurans using protocol 1 in conjunction with non-destructive gill swab samples was shown to give the best results.

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Genetic variation in parasite resistance of Atlantic salmon to amoebic gill disease over multiple infections

Cited by 58 publications

References 26 publications

Assessment of Genetic Correlation between Bacterial Cold Water Disease Resistance and Spleen Index in a Domesticated Population of Rainbow Trout: Identification of QTL on Chromosome Omy19

Assessment of Genetic Correlation between Bacterial Cold Water Disease Resistance and Spleen Index in a Domesticated Population of Rainbow Trout: Identification of QTL on Chromosome Omy19

Heritable variation in host tolerance and resistance inferred from a wild host–parasite system

Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

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