What causes white spot in farmed shrimp?


SeafoodSource staff

Published on
November 1, 2010

The white spot symdrome virus (WSSV) has baffled scientists for years, but Dutch researchers say they have identified the source of the disease’s aggressive nature, which has posed a major threat to Asia’s shrimp-farming industry over the past 20 years.

Published in the online edition of the journal PLoS One, the findings could lead to better containment of the virus, Wageningen University researchers said on Monday.

According to the scientists, the disease’s aggressive nature appears to be an evolutionary adaptation to shrimp-farming practices. Due to the virus spreading over long distances in a short timeframe, researchers also found that transportation of infected shrimp is the major cause.

Scientists analyzed samples of the virus in shrimp from five Asian countries and compared them to each other and previous studies published about Taiwan, China, Vietnam and Thailand. This allowed the researchers to clarify which genetic and fitness changes have occurred in the various virus populations since the virus was initially discovered.

Global shrimp production has tripled over the past two decades, from 750,000 metric tons in the 1990s to more than 3 billion metric tons annually over the past five years. Beginning in Taiwan in 1992, WSSV has spread across southern Asia in just several years, from China and Vietnam in 1993, to Thailand, Bangladesh and India in 1994 to Malaysia and Indonesia in 1996 to the Philippines in 1999.

Outbreaks in China in 1992 and Ecuador in 1999 resulted in a 70 percent reduction in shrimp production in the years following the outbreak. The virus has since spread globally and has even been found in wild crustaceans in Europe.

Researchers say preventing WSSV from spreading is a major area of improvement in combating future virus outbreaks in farmed shrimp.

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