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June 2, 2013

Vietnam

EMS from 210 to 2012

 

From Abstract: Acute hepatopancreatic necrosis syndrome (AHPNS), also called early mortality syndrome (EMS), first appeared on shrimp farms in the coastal provinces of the Mekong Delta in 2010.  It continued to occur in 2011 and 2012, causing serious mortality mainly in intensive and semi-intensive farms and spreading to some northern coastal provinces.  The disease occurs throughout the year, but it’s most severe from April to July, affecting ponds stocked with wild black tiger shrimp (Penaeus monodon) and domesticated Pacific white shrimp (Penaeus vannamei.  Incidences of AHPNS seem to be higher during the dry season when salinities and temperatures are higher. Results of environmental parameter tests showed that water quality is not the main cause of AHPNS.  Pesticide  residues (deltamethrin, fenitrothion) were detected in both affected and unaffected ponds,  However, experimental studies evaluating the effects of the most commonly used pesticide (deltamethrin) showed lethality at very low concentrations (from 0.001 μg/L to 0.1 μg/L), but no signs of typical AHPNS in the hepatopancreas (HP) of exposed shrimp.  The most common Vibrio bacteria found in the HP of shrimp from most infected ponds was V. parahaemolyticus, but treatment with antibiotics (oxytetracycline, florfenicol) was not effective.  Challenge experiments in laboratory conditions by either immersion of healthy shrimp postlarvae in the extracted HP of AHPNS shrimp for 14 days, muscular injection of 0.22 and 0.45 μm filtered extracted HP inoculums and feeding with either whole head or HP of AHPNS shrimp could not induce lesions of the HP consistent with the disease observed in growout ponds.  Infectivity studies with V. parahaemolyticus carrying phage and cohabitation experiments in culture ponds are in progress.

 

Source: The Thumb Drive Containing the Abstracts from Aquaculture 2013 (February 21-25, 2013, Nashville, Tennessee, USA).  Information: John Cooksey, World Aquaculture Conference Management, P.O. Box 2302, Valley Center, California 92082, USA (phone 1-760-751-5005, fax 1-760-751-5003, email worldaqua@aol.com).  Acute Hepatopancreatic Necrosis Syndrome (AHPNS) on Farmed Shrimp in The Mekong Delta, Vietnam.  Dang Thi Hoang Oanh (email dthoanh@ctu.edu.vn, Department of Aquatic Pathology, College of Aquaculture and Fisheries, Cantho University, Vietnam), Tran Viet Tien, Truong Quoc Phu and Nguyen Thanh Phuong.  February 2013.

 

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