Diseases affecting larval stages and juvenile fish have long been a major bottleneck in the development of barramundi farming. From an adverse Barramundi husbandry incident, Alain Michel empirically discovered that larval fish affected by VNN could be treated by daily heat-shock treatments during few days.
From this observation, Alain Michel proposed a new paradigm: “in aquaculture, it is an utopian dream to fully exclude pathogens from the environment; they are part of the aquaculture equation and so we should find a way to live with them”.
Methodically, protocols were then developed using heat-shock treatment and controlled presence of the disease to treat the other diseases of the larval and juvenile stages of barramundi. Once they were 5-10 g, they were healthy and resistant to several viral and bacterial diseases and could be vaccinated against S. iniae before transfer to sea cages. Several years later, heat-shock treatments were also developed directly in sea cages to address other common diseases. A complementary approach of heat-shock treatment and vaccination has since been the key to address major diseases observed during the barramundi farming life cycle.
In 2019, a massive iridovirus outbreak wiped out almost the entire commercial Tilapia production of Lake Volta (Ghana) (15,000 tons annual production). In collaboration with a large commercial farm, Tropofarms, Alain Michel developed a similar heating protocol to treat tilapia juveniles. This heat-shock treatment allowed the survival of Tilapia that could subsequently be vaccinated at 10 g against S. agalactiae, a deadly bacteria found not sensitive to heat shock treatments. Tropofarms continues to use the heat-shock therapy today and lives with the virus. Alain saved the tilapia industry in Ghana.
It is unlikely that all diseases can be controlled by heat-shock treatments. Heat-shock treatments were observed most effective in cases of viral infections and bacterial infections for which the optimal growth temperatures of the pathogens were below the heat treatment temperatures. It is probable that the heat-shock treatment is effective in these cases because it reduces pathogen replication, allowing the fish to mount an immune response. In tilapia farming, like in barramundi farming, the major diseases can be controlled by a complementary approach of heat-shock treatment and vaccination.
Today the methodology developed by Alain Michel is successfully used in many South-East Asia farms with several tropical species. Over the past years, Alain has also been testing his methodology on other aquatic species, both temperate and tropical.