Protection against CMS – Better heart helath

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Updated documentation, per July 2015

 

Cardiomyopathy syndrome (CMS), is a heart disease affecting salmon that is caused by Piscine myocarditis virus (PMCV). CMS often occurs late in the seawater phase affecting large fish and has become an increasing problem for the Norwegian aquaculture industry since 2010, with 107 cases registered in 2014. The use of QTL eggs that are selected for resistance to CMS is documented to provide significantly improved heart health that contributes to a more robust salmon.

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Figure 1. Effect on heart damage of QTL-innOva® CMS after disease challenge with PMCV on salmon of average 2.3kgs. The sum of grading for heart damage by histopathology (± standard error) is conducted on 68 fish for each gene variant. Fish with 1 (qQ) or 2 (QQ) copies of the beneficial marker that are included in QTL-innOva® CMS, had significantly reduced heart damage compared with the unfavourable gene variant (qq). The survey was carried out blinded, and by researchers at the Norwegian School of Veterinary science.

Development and results of QTL-innOva® CMS

Based on data and tissue samples from a field outbreak of CMS in 2008, there was found to be a very good correlation between virus level in the heart, heart tissue damage and mortality. The fish in the study were genotyped and a strong QTL was found that related to virus level in the heart. Effect of the QTL was subsequently tested and confirmed in both a field outbreak and a controlled disease challenge test. In one field outbreak in 2011 around 20% reduced mortality was recorded for fish with the CMS-QTL and an economic analysis showed that as little as 1% CMS related mortality was enough to justify the investment in CMS-QTL.

It was in 2012 that the offspring of the CMS resistant families from the CMS outbreak in 2008 were subjected to an infection challenge with PCMV in the laboratory. Heart damage was assessed using histopathology and once again there was significantly reduced damage in fish that had the CMS-QTL (Figure 1).

 

Field experience with QTL-innOva® CMS

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Figure 2. Growth and mortality after 8.5 months in the sea for salmon that have gene markers for CMS resistance (QTL-innOva® IPN/PD/CMS) and salmon without this gene marker (QTL-innOva® IPN/PD). Fish populations came from the same hatchery, were transferred in September 2014 and went into several separate cages in two locations. There was a diagnosis of HSMI in IPN/PD fish in cage 4 at location B.

Autumn 2014 was the first time that S0 smolt were transferred of QTL-innOva® IPN/PD/CMS and QTL-innOva® IPN/PD in two locations that had a history of CMS outbreaks. Until now, CMS has not been recorded in any of the fish groups in these locations.

Following 8.5 months in the sea, at location A, good growth was recorded for all fish groups. At location B there is a tendency for better growth of fish type QTL-innOva® IPN/PD/CMS. On both locations there is on average a lower mortality rate for fish of QTL-innOva® IPN/PD/CMS (Figure 2).

 

Better heart health gives more robust salmon

In QTL-innova® CMS the most CMS sensitive individuals (qq) are eliminated from the population. This will result in an increased barrier to the introduction and spreading of PMCV in the population, which will therefore be more robust to stress like lice treatment, transport and storage in stand by cages.

Products with CMS protection:

  • AquaGen® Atlantic QTL-innOva® IPN/CMS
  • AquaGen® Atlantic QTL-innOva® IPN/PD/CMS
  • AquaGen® Atlantic QTL-innOva® IPN/CMS/RED
  • AquaGen® Atlantic QTL-innOva® IPN/PD/CMS/RED

Benefits of QTL-innOva® CMS:

  • Reduced virus levels in the heart, reduced heart damage and lower mortality from CMS outbreak
  • Higher degree of herd immunity by the elimination of the most susceptible individuals
  • Robust fish that withstand transport and handling better in the final phase of production