Fish resistance to lethal virus linked to genetics

Thursday 27th February 2020, 4:00pm

Resistance to a deadly disease in Tilapia fish is mainly caused by genetic differences between families of the same fish.

Immune cells - credit Roslin Innovation Centre

The deadly Tilapia Lake Virus (TiLV) is very heritable, scientists found. This means that selective breeding to produce more resistant tilapia strains is likely to be effective.

The findings could help protect stocks of Tilapia fish, which is the second most farmed fish in the world. It is an important food source in Africa, Asia and South America, and worth nearly $10 billion to the global economy.

Researchers from the Roslin Institute and WorldFish analysed the genes of 1,821 Genetically Improved Farmed Tilapia (GIFT), which were tagged and placed in a pond that had an outbreak of TiLV.

The fish were members of 124 families and the team discovered that there was a large variation in family survival. Some family groups had no deaths, whereas others found to have a 100 per cent death rate.

Future breeding programmes for GIFT that produce fish resistant to the virus will not adversely affect the growth of the fish and will benefit farmersí yields, the researchers found.

The GIFT strain has been selectively bred to be fast growing and adaptable to a wide range of environments. The strain is produced in at least 14 countries, helping to reduce poverty and hunger.

Since its detection in 2014, TiLV has ravaged Tilapia populations in 16 countries across three continents. There are currently no treatments or vaccines for TiLV, which causes a variety of symptoms in Tilapia. These include behavioural changes, discoloration, skin hemorrhages, loss of scales, eyeball protrusion and abdominal swelling, with up to 90 per cent of fish dying once infected.

"Tilapia Lake Virus poses a real problem to fish famers worldwide, impacting on the livelihoods and food security of millions of people. This research is the result of a long term collaboration between Roslin and WorldFish, and is the first step to breeding Tilapia strains with improved resistance to the virus."

Professor Ross Houston, lead author and Personal Chair of Aquaculture Genetics, The Roslin Institute