Since Shrimp Early Mortality Syndrome (EMS) / Acute Hepatopancreatic Necrosis Syndrome (AHPNS) emerged in China in 2009, many monodon and vannamei deaths have been reported in several Asian countries, especially in China, Vietnam, Malaysia, and Thailand. Many, if not all, infected post-larvae (PL) die within 30 days of farming. In 2013, Thailand expected shrimp farming production would decrease by 30% or even up to 60% in certain regions. (FAO, 2013)

Pathogeny tests in these shrimp identify vibrio infections (V. parahaemolyticus, V. harveyi, or V. vulnificus) in their livers or pancreases. Bacteriophage and other viruses (WSSV, YHV, TSV or IHHNV) are also identified. However, symptoms are not triggered by these viruses. Lightner (2013) points out that if healthy shrimp are infected by V. parahaemolyticus, EMS/AHPNS symptoms will appear. If certain bacteriophages exist at the same time, shrimp will die. This combination creates toxins and impacts livers and pancreas. The mechanism is similar to cholera infections in humans, as Vibrio cholerae and bacteriophages both trigger lethal diarrhea.

Shrimp with EMS/AHPNS are inactive or swimming in circular paths, especially vannamei. Diseased shrimp also eat less and grow slower; their stomachs and intestines are empty; their livers and pancreases are pale and shrinking with black lines. When observing tissues, mitosis activities appear insufficient in E-cells in livers and pancreases, while B, F, R cells exhibit functional disturbances. Epithelium of nephric tubules falls off extensively. (Lightner et al., 2012).

Juvenilie Penaeus Vannamei from Vietnam. Left with EMS; right appears normal. (Photo by Dr D. V. Lightner)

Biopsy of Penaeus Vannamei infected with EMS/AHPNS displays pathological changes in hepatopancreas. (Photos by Dr T. W. Flegel)

Water quality indicators: ammonia < 0.3 ppm, nitrite < 1 ppm, DO > 4 ppm, pH 7.5-8. When water quality is abnormal, apply Grobest PSB and EM products to improve water quality, and use functional feed.