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May 21, 2014

United States

Missouri—GAA Epidemiological Study of EMS

 

At recent conference in Washington DC, Dr. George Chamberlain, head of the Global Aquaculture Alliance (GAA), briefed National Fishery Institute members on the current status of early mortality syndrome (EMS) on shrimp farms around the world.  His country-by-country report reviewed the status of EMS the during the spring of 2014:

 

China: Five growing areas are showing low to moderate incidence of EMS, while two regions, the Pearl River and Zhanjiang in southern Guangdong province, have a moderate to high incidence of EMS.  One of the difficulties in China is that other diseases can be mistaken for EMS.

 

Vietnam: High prices have caused farmers to stock at high densities, despite the continued presence of EMS.  As prices drop, however, farmers stock fewer ponds.

 

Thailand: Thailand is again experiencing significant problems with EMS.  At many farms there is a failure rate of over 30% in the first 40 days of growout.  In addition, three months of cool weather have reduced production.  As a result, first quarter production was only around 30,000 metric tons, compared to 100,000 tons last year.  Like Vietnam, reduced prices are causing some farmers to stock fewer ponds.

 

Malaysia: In most areas production is still down, but large farms operated by Agrobest are seeing steadily improving results.

 

Mexico: EMS continues to be reported in Sinaloa and on some farms in Sonora.  New farms are being started in the east coast states of Tamaulipas, Campeche, Tabasco, and Yucatan, all on the Gulf of Mexico and far away from the shrimp farms on the west coast that have been hit with EMS.

 

India: Recent reports from India have been quite positive, as tests at shrimp farms in Andhra Pradesh and Tamil Nadu found “no signs of EMS.”  These tests were supervised by Dr. Lightner of the University of Arizona, who helped discover the pathogen and develop the DNA tests for it.

 

Indian, Indonesia and Ecuador, all EMS free, are now the primary shrimp producers in the world, and they are all increasing production.

 

The next step in global control of EMS will be a major epidemiological study to identify the best practices for avoiding EMS at farms, hatcheries and broodstock facilities.  This phase will be funded by the World Bank’s Allfish Project, the Seafood Industry Research Foundation of the National Fishery Institute, and CP Prima of Indonesia.  GAA will provide project management for the epidemiological study, which will begin with a comprehensive survey to determine how farms were affected by EMS—and whether the impacts were low, moderate or high.  The results of that survey will be compiled, and BAP auditors will visit selected farms to validate practices that provided positive and negative results.  Languages of the study will be Mandarin, Thai, Vietnamese, Bahasa (Malaysia), Spanish, and some Indian dialects.  The results will be presented at the GAA GOAL meeting in Vietnam October 7, 2014.

 

An expert committee has been formed to oversee the project, and its members have already provided the following information on EMS:

 

• There are multiple strains of EMS with varying levels of toxicity.

 

• EMS is often confused with other diseases such as whitespot and Taura.

• Once EMS is established in the environment, it is hard to control because it is transmitted by shrimp eating infected material in the ponds.

 

• Reducing pond sludge is one positive control mechanism.

 

• Antibiotics are not effective. The EMS pathogen has already developed resistance to almost all antibiotics.

 

• Some feed additives may have a positive protective effect.

 

• An intensive broodstock breeding program is recommended, where parents are exposed
to EMS and the best survivors are selected to reproduce again.  One intent of this is to
determine the heritability of EMS resistance.

 

• Hatchery feeds, like marine worms and oysters, may be carriers that can infect broodstock.
Also some local shrimp may be asymptomatic carriers.  The biosecurity of hatcheries will
have to be increased.

 

• At the farm level, bioflocs, polyculture with tilapia and controls on feeding may diminish the
effects of EMS.

 

GAA and the World Bank are working to identify some common issues with aquaculture disease outbreaks.  Some of the issues that are common to aquaculture epidemics include close proximity among farms, unregulated movement of animals, lack of sanitary protocols and poor information sharing.  This suggests that zone management which includes proper siting of farms, and step-by-step production controls on transport would go a long way to secure shrimp production.

 

All in all, it appears that the surge in production in the unaffected areas—India, Indonesia and Ecuador—will significantly ease the supply shortages experienced in 2013, but for the long term, viable disease management strategies that can be applied on a country-wide scale will need to be adopted, just as they were when the whitespot virus devastated farmed shrimp production in the early 1990s.

 

Information: Dr. George Chamberlain, Global Aquaculture Alliance, 4111 Telegraph Road, Suite 302, St. Louis, Missouri 63129, USA (1-314-492-5058, mobile: 314-607-8466, email georgec@gaalliiance.org, webpage www.gaalliance.org).

 

Source: Seafood.com (an online, subscription-based, fisheries news service).  Editor and Publisher, John Sackton (phone 1-781-861-1441, email jsackton@seafood.com).  Major Effort to Control EMS Continues Through Second Phase, With Report Due at GAA Mtg in Vietnam.  John Sackton.  May 20, 2014.

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