October 15, 2007

Less stress the way to shrimp disease prevention, Taiwan research reveals

Shrimps are most vulnerable to White Spot Syndrome Baculovirus Complex(WSSV), during times of stress, such as when they are spawning, according to researchers from National Taiwan University (NTU)

This and other findings have been revealed by genetic analysis of the virus that once decimated shrimp stocks in the nation.

Aquaculture researcher Lo Chu-Fang, who heads the study, said that farmers could do much to prevent the disease through better aquaculture practices.

During periods of stress, such as when spawning, the level of WSSV increases in the shrimp's body 100,000-fold.

Local shrimp-rearing methods put a lot of stress on shrimp stocks because local shrimp farmers tend to adopt a very intensive approach, Lo said.

A million shrimp could be kept in a hectare of aquaculture pond in Taiwan when 300,000 to 400,000 is the norm.

She said that not only were crowded shrimp more susceptible to WSSV, the conditions may have actually caused the condition in the first place.

WSSV did not appear until 1992, and Lo's research found that previously the virus was an obscure and largely harmless one affecting certain species of crab.

However, once the virus started affecting farmed shrimp, it spread rapidly.

Lo's research, which includes the discovery of a way of testing for WSSV, has helped some shrimp producers abroad reduce WSSV losses from up to 80 percent to less than 5 percent. The team is currently working on a vaccine.