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June 11, 2013


Will a Nanotech Silver Solution Prevent EMS?


Two diseases—the whitespot virus and early mortality syndrome (EMS), called acute hepatopancreatic necrosis syndrome, or AHPNS, by the scientific community—cause high mortalities on Vietnamese shrimp farms.


EMS/AHPNS is caused by a bacteria (Vibrio parahaemolyticus) that’s infected with a virus (a phage) and transmitted orally.  Together, they colonize the shrimp’s gastrointestinal tract and produce a toxin that causes tissue destruction and dysfunction of the hepatopancreas, the shrimp’s digestive organ.


Tests carried out by the Pasteur Institute/Vietnam and Vietnam’s Southern Monitoring Centre for Aquaculture Environment and Epidemics, part of the Research Institute for Aquaculture No.2, have shown that a nanotech silver solution has the ability to kill several bacteria including Vibrio cholera, E. coli, and V. parahaemolyticus.  It might even stop of growth of blue-green algae.


Experiments with the silver solution at the Laboratory for Nanotechnology (LNT), part of the Viet Nam National University in HCM City, and at a large shrimp farm belonging to the HCM City University of Agriculture and Forestry in Thu Duc District have shown that the solution improves water purity significantly.  In tanks with the silver solution, 85 percent of the shrimp were alive after 53 days, while all shrimp in tanks without the solution died.


Currently, the silver solution is being tested at the Thai Tuan Shrimp Farm in HCM City’s Can Gio District and at the shrimp farms of the Hoang Vu Company in Ben Tre Province.  Scientists from LNT have also visited farms in Bac Lieu Province and hope to test the solution there.


Le Van Tuoi, owner of the Thai Tuan Shrimp Farm in HCM City’s Can Gio District, says he has lost around $152,380 in the past two years because his shrimp have been dying in large numbers.  “My shrimps were living for less than 30 days,” he said.


Tuoi met Associate Professor Dang Mau Chien, director of LNT, when Chien visited shrimp farms in his district more than a month ago.  Tuoi decided to allow the scientists to test the silver solution in his ponds.  Two of his three 4,000-square-meter shrimp ponds (0.4 hectare) were treated with the solution.  As a control, the third pond was not treated.  After a month, the shrimp in the two ponds treated with the silver solution were healthy, feeding well and growing quickly.   The shrimp in the pond that was not treated with the solution suffered from the symptoms that showed they were easily susceptible to diseases, and their general condition worsened.


Scientists said they could not answer questions about the cost and safety of the silver solution until more tests were conducted.  Nonetheless, Tuoi said that one liter of the solution would cost about $9.50 in the open market and that it would take 150 liters to treat a 4,000-square-meter pond ($9.50 x 150 = $1,425).  The treatment would have to be applied three times ($1,425 x 3 = $4,275) for each crop.  Chien said LNT would be able to supply the solution at half the market price ($2,137).  Tuoi also said that without using the silver solution, it took 60 days for 200 shrimp reach one kilo, but that weight was achieved in 32 days with the solution.


Information: Dang Mau Chien, Vietnam National University, Laboratory for Nanotechnology, Community 6, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, Vietnam (phone 84-8-3724-2160, extension 4621, fax 84-8-3724-2163, email, webpage


Source:  Can Nanotech Save Dying Shrimp Farms?  June 6, 2013.


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