REVISITING HATCHERY BIOSECURITY AND RISK MANAGEMENT

Craig L. Browdy, Diego Flores, Peter Van Wyk and Susan Laramore
Zeigler Aquaculture Research Center
 Harbor Branch Oceanographic Institution Florida Atlantic University
 5600 North US HWY 1, Fort Pierce, FL 34946
 

Emerging shrimp pathogens are increasingly prevalent in hatcheries worldwide, resulting in increased health risks for the shrimp aquaculture industry.  PL health and quality are critical to hatchery profitability. Many hatcheries are rigorously screening for diseases and  tightening their biosecurity protocols to ensure the health of their postlarvae. The prevention of stocking diseased postlarvae into growout ponds is critical to achieving good survivals.  For decades, viral diseases have been the dominant disease threat to the industry.  Since the early days of Baculovirus penaeii hatchery mortalities and IHHNV related stunting, most hatcheries have focused on exclusion, and the use of specific pathogen free (SPF) breeding stocks to control disease.   More recently, breeding programs have focused on developing disease resistant genetic lines.  However, the emergence and spread of virulent bacterial disease coupled with stubborn microsporidian infections have made disease management much more complicated.

Acute Hepatopancreatic Necrosis Disease (APHND) spread quickly through the Asian shrimp industry before the causative agent was finally diagnosed.  EMS was found to be caused by a virulent strain of Vibrio parahemolyticus carrying plasmids with genes encoding for powerful toxins causing necrosis of the hepatopancreas. In Ecuador, the disease has become a serious problem in hatcheries causing rapid and severe mortalities in young PL.  While vibriosis has always been a major cause of mortalities in hatcheries, the emergence of new more virulent strains makes the control of bacterial pathogens more important than ever.  Enterocytozoon hepatopenaei (EHP) causes a disease characterized by slow growth and increased susceptibility to infections. This microsporidian is an intracellular parasite that produces spores which are extremely difficult to eradicate, leading to their buildup in the culture environment if not controlled.  

Refocusing hatchery biosecurity entails continual risk assessment and risk management based on the most up to date information on pathogens and control strategies. Hazard analysis and critical control point (HACCP) methods. Using HACCP methods, mechanisms of transmission and amplification can be identified and controlled to eliminate excludable pathogens and to prevent the buildup of non-excludable bacterial pathogens, both in the hatchery and at the farm.  Treatment of incoming water and management of water systems and effluents can minimize introduction and buildup of bacteria and spores in the hatchery.    Broodstock can be another significant vector of disease, necessitating quarantine and rigorous disease testing prior to their introduction into maturation production systems.  Fresh and live maturation feeds have also been shown to be important vectors for introducing pathogens into hatcheries.    Many hatcheries are finding that the use of probiotics and partial replacement of live and fresh feeds with high quality prepared diets with disease free fresh feed supplements can significantly reduce the loading of pathogens in their maturation and larval rearing systems, leading to more consistent larval heath.  The future of shrimp farming will require continued scientific advancement in pathology, genetics, innovative nutrition and hatchery management.