Farmed shrimp. (Photo: VASEP)

Shrimp farm crops suffer from EMS outbreaks

THAILAND
Friday, January 18, 2013, 02:40 (GMT + 9)

Shrimp farms across eastern Thailand have been viciously struck by outbreaks of EMS (early mortality syndrome), also known as AHPNS (acute hepatopancreatic necrosis syndrome), and the situation seems worse than reported.

Daniel Gruenberg, CEO of Sea Garden Foods, said he has visited his company’s main shrimp farming areas in eastern Thailand, from Pattaya, through Rayong and all the way to nearby Trat Province on the Cambodian border to study the situation.

“I estimated that a minimum of 80 per cent of shrimp ponds in this key production area were dry! Even more shocking, no one was talking about why the ponds were dry. Are we ostriches with our heads in the sand, hoping that the early mortality problem will just go away?” wrote the businessman on Shrimp News International forum.

Gruenberg expressed disappointment as far as experts’ attempts to explain the problem at the recent EMS symposium in Bangkok, calling attendees’ theories “a lot of nonsense.”

The three largest hatcheries in the region have confirmed to him that EMS has been killing their postlarvae as well as their broodstock, he told, which for him it means that other processors are also having problems when acquiring products for their shrimp ponds.

“From all the evidence that I have seen, the problem is much larger than the industry is willing to admit,” Gruenberg stated.

As for the desease impact on Sea Garden Foods’ farms, he said, the company has been implementing its own R&D programme, although it is too early to tell whether it will be successful. The efforts focus on practical methods for tackling EMS infections as well as preventing them.

So far, three causes of EMS have been proposed: an unidentified virus, a toxin in phytoplankton or zooplankton that is transmitted on oceanic currents and a genetic loss that previously provided shrimp with disease resistance, according to Leland Lai of California, US-based Aquafauna Bio-Marine.

“I have a strong suspicion that EMS involves immune suppression based on inbreeding depression,” Gruenberg noted. “I am going to test that theory by obtaining male and female pairs from disparate sources and genetic backgrounds, breeding them, and then growing them to see if they are resistant to EMS.”

He added that if there are environmental etiological agents, perhaps a virus, they may not express themselves until the shrimp are stressed.

He pointed out that maybe it is time for shrimp farmers to concentrate on the monodon variety (Penaeus monodon), the giant tiger prawn, given that there are no reported symptoms of this disease in this variety of shrimp, unlike what happens with the white shrimp (P. vannamei).

By Natalia Real
editorial@fis.com
www.fis.com

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