In about 2009, a new shrimp disease called early mortality syndrome (EMS) or acute hepatopancreatic necrosis disease began to cause significant production losses in southern China. By 2012, farmers in Vietnam, Malaysia and Thailand reported crop losses of up to 90 percent due to EMS.
The Responsible Aquaculture Foundation undertook a case study funded by the World Bank in 2012 to analyze the EMS crisis in Vietnam. The RAF team visited hatcheries, farms and research facilities throughout Vietnam, conducted interviews and gathered samples.
The small, low-intensity shrimp farms typical of Vietnam tended to maintain culture water quality via water exchange using common water supplies. Oversight of transfers of broodstock and seedstock was haphazard. This structure quickly spread EMS. A lack of coordinated information sharing and crisis response among the farms led to many misguided and ineffective remedies.
Environmental toxins were initially suspected to cause EMS, but the RAF team, which included Dr. Donald Lightner of the University of Arizona, eventually determined that a Vibrio bacteria strain colonized the digestive systems of young shrimp and produced a toxin that killed them. This led to progress in developing diagnostic tools and better understanding of techniques for managing the disease.
Diagnostic testing lagged far behind the EMS outbreak in Vietnam, and producers and regulators were slow to respond. The study highlighted the importance of cooperative action among farmers, government regulators and researchers, and the open sharing of data in identifying the causes and possible solutions for aquatic animal diseases.
The ultimate solution will require improved controls for breeding, hatchery, farm and feed, as well as effective coordinated area management.