SEAFOOD.COM NEWS by John Sackton — April 2, 2014 — Professor Ikuo Hirono of Tokyo University is one of the scientists who, along with Donald Lightner at the University of Arizona has worked to overcome the effects of the EMS disease in shrimp.
Lightner demonstrated that EMS was in fact a particular strain of a common bacteria, Vibrio parahemolyticus. To assist shrimp farmers, a test was needed that would distinguish between the harmless Vibrio that is present in the environment, and the Vibrio with the EMS strain.
Professor Hirono decoded the EMS genome at Tokyo University, and this has been a key breakthough in developing PCR tests.
So far, these PCR tests have generally been done in fisheries laboratories in Thailand, Indonesia, and Vietnam.
Methods have been developed to use the test in Thailand and Taiwan, but they all produce a high rate of false positives – around 10%.
As a result, a tighter PCR test is needed, which Professor Hirono told Nikkan Suisan Keizai Shimbun that he is about to introduce.
For other shrimp diseases, the World Organization for Animal Health has 'gold standard' detection methods, which are proven tests that can be used to identify a disease. Professor Hirono hopes that his PCR test will become this gold standard.
His test is based on identifying several types of DNA, thereby reducing the false positives.
Once this test is widely available, farmers should be able to immediately determine if EMS exists in the Vibrio in a given pond or not, before they stock the pond.
Currently Japanese analysts think that the May / June harvest in EMS affected areas in Thailand and Vietnam will be low, because many farmers have reduced their density and remain cautious about committing their expensive juvenile shrimp without better assurance they will not get disease. These analysts expect the surge in production to materialize with the second crop, when hopefully these PCR tests will be more widely available.
In Thailand, reports NSK, some think the chinese sand worms (lug worms) that are widely distributed and used for feed for shrimp broodstock, may have been a tranmission factor. These worms are distributed world wide, and fed live to breeding shrimp, as it helps them produce very healthy eggs.
Thai authorities have taken steps to control the dissemination of these worms as shrimp feed.
This story originally appeared on Seafood.com, a subscription site. It is reprinted with permission.