• 29th Sept, 2012


    • SAP meeting on EMS Shrimp Early Mortality Syndrome (EMS) /Acute Hepatopancreatic Necrosis Syndrome (AHPNS) SAP has organized an awareness programme on the Early Mortality Syndrome (EMS) at Chennai on 29th September. Dr.Alavandi gave a presentation. Excerpts

      An emerging disease known as early mortality syndrome (EMS) or acute hepatopancreatic necrosis syndrome (AHPNS) has been recently causing significant losses in shrimp farms in China, Vietnam, Malaysia and Thailand since 2009. The disease affects both black tiger shrimp Penaeus monodon and Pacific white shrimp, P. vannamei and is characterised by mass mortalities during the first 20-30 days of culture after stocking.

      Considering the severity of the disease, the Network of Aquaculture Centres in Asia-Pacific (NACA) jointly organized an emergency regional consultation on EMS/AHPNS with the Australian Department of Agriculture, Fisheries and Forestry (DAFF), Australia, in Bangkok, on 9-10 August 2012, to share information on this emerging disease, its occurrence, pathology and diagnosis, and to develop a coordinated regional response. Eighty-seven (87) participants including international shrimp health experts, regional governments and industry participated in the consultation. The expected outputs of the consultation included increasing awareness on EMS, disseminate current knowledge on EMS to the participants, define case definition of EMS, identify the causative agent, suggest preventive and control measures, and improving surveillance, monitoring and reporting.

  • April 2012


    • History of EMS / AHPNS and its impact

      During the two day expert consultation, representatives from Vietnam, China, Malaysia and Thailand shared their experience on EMS. In Vietnam, the disease was observed since 2010, but the most widespread devastation due to EMS was reported since March 2011 in the Mekong Delta (South Vietnam). EMS affected the main shrimp production areas of Tien Gang, Ben Tre, Kien Giang, Soc Trang, Bac Lieu and Ca Mau provinces with a total shrimp pond area of around 98,000 hectares. In June 2011, unprecedented losses in P. monodon were reported in 11,000 ha of shrimp farms in Bac Lieu, 6,200 ha in Tra Vinh (causing a loss of over VND12 billion), and 20,000 ha in Soc Trang (causing VND1.5 trillion in losses) (Mooney, 2012). With Vietnam suffering the greatest loss due to EMS outbreak, the Food and Agriculture Organization of the United Nations (FAO) undertook an emergency mission in 2011 to assess the disease situation in the country, in collaboration with national and international shrimp health experts. As a follow-up on this emergency mission, FAO developed a national Technical Cooperation Programme (TCP) on emergency assistance to control the spread of this shrimp disease. Implementation of the national TCP in Vietnam commenced in April 2012.

      In China, the occurrence of EMS in 2009 was initially ignored by most farmers. But in 2011, outbreaks became more serious especially in farms with culture history of more than five years and those closer to the sea using high saline water (Panakorn, 2012). Shrimp farming in Hainan, Guangdong, Fujian and Guangxi suffered during the first half of 2011 with almost 80% losses.

      In Malaysia, EMS was first reported in mid-2010 in the east coast of peninsular states of Pahang and Johor. The outbreaks of EMS resulted in significant drop in P. vannamei production, from 70,000 mt in 2010 to 40,000 mt in 2011. Production for 2012 (up to May) was only 30,000 mt and worse was expected to come as unconfirmed reports on EMS outbreaks in the states of Sabah and Sarawak came in April 2012. In Thailand, so far 0.7% total shrimp ponds were reported to be affected by EMS, in Rayong, Chantaburi, Trat, Chacheongsao provinces located along the eastern Gulf.

  • 29th Sept, 2012


    • Investigations on EMS/AHPNS and their findings

      Pathology of EMS / AHPNS was explicitly described by Dr. DV Lightner of University of Arizona, in both P. monodon and P. vannamei and he informed that the pathology appeared to be limited to the hepatopancreas (HP). He described EMS / AHPNS as idiopathic since no specific disease causing agent (infectious or toxic) was so far found to be associated. The clinical signs such as significant atrophy of the HP, which may be often pale to white due to pigment loss, sometimes with visible black spots or streaks, which does not squash easily between the thumb and forefinger could be used for presumptive diagnosis in cases of shrimp mortality starting as early as 10 days post-stocking. Progressive degeneration and dysfunction of the HP tubule epithelial cells progressing from proximal to distal ends of HP tubules and its degenerative pathology suggested of a toxic etiology. However, he also mentioned that the anecdotal information suggested that disease spread patterns may be consistent with an infectious agent.

      According to Dr. Tim Flegel of CENTEX shrimp, in the EMS affected shrimp, in addition to various well studied pathogens such as WSSV, YHV and vibrios that are commonly linked to EMS, they also found certain groups of bacteria using metagenomics tools. While the role of certain crustaceacides such as cypermethrin was ruled out, he mentioned that the disease transmission trials were inconclusive.

      According to Dr Peter Walker of CSIRO, the potential pathogens are integral components of all ecosystems and disease emergence and subsequent spread often resulted from some disturbance in the ecology, which can upset the natural balance resulting in a normally innocuous organism emerging as a new disease agent. He mentioned that the current aquaculture practices, which are artificial and un-natural high density culture activities, promote emergence of pathogens. Understanding biological and ecological drivers of pathogen emergence can help in reducing or limiting the impact of emerging infectious diseases. Considering the need for identifying the etiology of EMS / AHPNS of shrimp, Dr Jeff Cowley of CSIRO in his presentation on the molecular tools for discovering unknown pathogens mentioned that a number of new methods such as sequence-assisted and sequence-independent virus discovery that could be applied to help discover viruses or other pathogens if these are the cause of AHPNS.

      The epidemiology and risk factors involved in EMS / AHPNS required systematic studies. Dr Flavio Corsin and Dr Matthew Briggs opined that until epidemiological approaches are applied systematically to include hatchery, transport, pond, farm and location specific data, it will be very difficult to pinpoint and prioritize risk factors for AHPNS. The potential risk factors included most of the generic factors such as high stocking densities, older farms closer to the sea using higher salinity water, farms not employing reservoirs, farms overusing chemicals, inadequate aeration, and presence of toxic levels of H2S etc.

  • 29th Sept, 2012


    • Summary and recommendations

      For the purpose of detection and surveillance of EMS / AHPNS, the definition proposed by Prof Don Lightner, which relies mainly on histopathology of hepatopancreas may be employed along with the clinical signs. It is important that histological examination be carried out to confirm that suspected occurrences fit the AHPNS case definition devised by Dr. Lightner. Identifying the primary cause of EMS / AHPNS is necessary and can be addressed by robust scientific programme. Until this information becomes available, every shrimp producing country in the region must increase disease awareness among the shrimp farmers. Considering the great economic loss that EMS is likely to cause in the region’s shrimp aquaculture, ways of preventing the spread and/or occurrence of this disease should be formulated by concerned experts, officials and other regulatory bodies. Farmers, on the other hand, should also cooperate with the concerned agencies by promptly reporting any suspected mortalities among cultured shrimp that appear to be similar to the clinical description of EMS / AHPNS.

      Considering the way the EMS / AHPNS has spread, it is necessary to impose restrictions on movement of live affected animals to areas free from EMS either for culture or for processing purposes, and movement of live shrimp may be undertaken only after conducting robust import risk analyses. A regional emergency aquatic animal disease fund may be created and an investigation initiated soon for understanding the etiology, prevention and control of EMS that may be coordinated by a regional body such as NACA.