White Feces Syndrome (WFD) has been an idiopathic disease causing significant economic losses for shrimp farmers in Asia. The syndrome is characterized by transformation and sloughing of microvilli of the hepatopancreatic tubule epithelial epithelium leading to the accumulation of aggregated, transformed microvilli (ATM) in the tubule lumens (Sriurairatana et al., 2014), white fecal materials in the gut, and the floating feces on the pond water surface. Since 2017, the ShrimpVet lab has been working on transmission models for WFD with focus on bacterial etiology. Based on initial result of these studies, several management strategies have been applied, including: algal bloom control, better feed management, application of probiotics application, better bio-remediation strategies, and functional diets. Those studies have proven effective to reduce WFD both in the laboratory and grow out in pond conditions.
Early Mortality Syndrome (EMS) or Acute Hepatopancreatic Necrosis Disease (AHPND) have been characterized and determined with the pathogens since 2013. Since then, there ShrimpVet lab has been made several attempts in order Vietnam to reduce the impact of AHPND in productions. These includes: better hatchery, nursery, and grow out protocols. With regards to hatchery protocols, several improved practices have been applied including: PCR screening for all material (brood stock, live feed, Nauplii, and post larvae before harvest), better sanitation, better bio-remediation with focus on Vibrio the reduction of vibrios. The same sanitation, probiotics, and bio-remediation approaches have been applied in nursery and grow out practices. Several trials using "functional diets" with feed additives added in feed ingredients before extrusion showed positive result in both disease prevention and growth performance. An overall antibiotic-free farming protocol is achievable.
In practice, Vietnam has been moving a long way from a very natural based farming system with less biosecurity and antibiotics-based farming protocols to a more controlled farming methods since the outbreak of EMS/AHPND in 2010 and EHP in 2014. Several new practices have been applied including: screening for diseases (EMS/AHPND, EHP, WSSV) through out the farming cycle, better pond preparation with good probiotics blooms before stocking, plastic-lined pond farming protocol, nursery phase at the farm level, routine/daily application of bioremediation, daily shrimp pond waste removal, probiotics top-coating in feed, and functional feed. With better adaptation to new farming protocols, it appears that the shrimp farming becomes more predictable, explaining the fast increase of Vietnamese shrimp production in recent years.