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November 10, 2015

The World

Dr. George Chamberlain on EHP


According to Dr. George Chamberlain, President of the Global Aquaculture Alliance (GAA), Enterocytozoon hepatopenaei (EHP), the disease that has emerged as a major risk to shrimp farmers in Asia, is unlikely to impact farmed shrimp production on the scale that early mortality syndrome (EMS) did.


Unlike EMS, EHP is caused by a spore.  This means that even though it spreads fast locally, it should be easier to contain it on a global scale, with the chance of it spreading to Latin America unlikely, said Chamberlain.


He said EHP is unlikely to decimate shrimp volume in the same way as EMS, because EHP—a microsporidian disease, caused by a spore rather than a bacteria or virus—generally does not cause mortality, but leads to severe growth retardation in heavily infected shrimp.  The effect of EHP—slower growth—isn’t noticeable until the shrimp reach 8 to 12 grams, at which point they are big enough for farmers to sell.  Chamberlain said EHP will make it harder to produce big shrimp, so we may see a trend toward more smaller shrimp coming out of Asia.


EHP is now present in China, Vietnam, Thailand, Malaysia and India, and possibly in the Philippines and Indonesia.  The EHP spore is resistant to chlorination, and it can spread quickly within a region from hatcheries to farms.


Chamberlain first observed EHP in Chinese shrimp, which he said have been hit the hardest and the longest.  Farmers there reported significant size variation.  “Size variation is normal...[but when] I looked at the Chinese shrimp, they showed me shrimp from 2 to 20 grams, an enormous difference,” said Chamberlain.  Normal size variation is generally between one and three grams.


EHP has not spread to the Americas, and, according to Chamberlain, there is hope that it will stay that way because of the nature of the disease and improved biosecurity measures.


EHP is killed by high temperatures and freezing, so in order for the disease to travel with the shrimp, they would have to be transported live, said Chamberlain.  He noted, however, that the disease can also be spread on live feeds, like marine worms, that are used in hatcheries.  “Live worms are often harvested from areas where shrimp farming occurs, so you can immediately see the cross contamination problem,” he said.  “One of the big challenges is to change our practices and discontinue the use of live worms.”


Source:Undercurrent News [eight free news reads every month].  Editor, Tom Seaman (  Chamberlain: New shrimp disease unlikely to hit production on scale of EMS.  Ola Wietecha (  November 9, 2015.


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