Dr. Lightner with six co-authors publishes definitive cause and analysis of EMS disease Dr. Donald Lightner of the University of Arizona and six co-authors have published a peer reviewed study that identifies the causes of EMS, (known scientifically as acute hepatopancreatic necrosis syndrome (AHPNS) and fully replicates the pathology in the laboratory. The studies were based on field work done in Vietnam, and were based on the fact that only live or never frozen shrimp could be used to identify and determine the cause. Both injecting shrimp muscle and using frozen material were not suitable to replicate the disease. However, in early 2013, the Aquaculture Pathology Laboratory at the University of Arizona was able to isolate the causative agent of AHPNS in pure culture. Immersion challenge tests were employed for infectivity studies, which induced 100% mortality with typical AHPNS pathology to experimental shrimp exposed to the pathogenic agent. Subsequent histological analyses showed that AHPNS lesions were experimentally induced in the laboratory and were identical to those found in AHPNS-infected shrimp samples collected from the endemic areas. Bacterial isolation from the experimentally infected shrimp enabled recovery of the same bacterial colony type found in field samples. In 3 separate immersion tests, using the recovered isolate from the AHPNS-positive shrimp, the same AHPNS pathology was reproduced in experimental shrimp with consistent results. The disease initially attacks the hepatopancreas in shrimp before there are any signs of the bacteria in that organ, suggesting that toxins in the stomach of the shrimp produced by the colony of bacteria are the cause. In later stages, only the hepatopancreas is affected with lesions and degeneration. The causative bacteria has been isolated as Vibrio parahaemolyticus, and a detailed study of that bacteria will be forthcoming. The article was published in the DISEASES OF AQUATIC ORGANISMS on July 9th. A copy of the full paper was published by Shrimp News here. What made AHPNS so hard to initially identify was that first, shrimp cannot be infected with an injection into muscle, and secondly, freezing apparently disactivates the bacteria in some fashion, so that only live or fresh shrimp can be used for the investigations. That is why the field work in Vietnam became critical for the effort. The authors thank CP Foods, Bangkok, Thailand; Uni-President Feed Company, Ho Chi Minh City, Vietnam; Grobest Industrial (Vietnam) Company, Dong Nai Province, Vietnam; Minh Phu Seafood Corp. Ho Chi Minh City, Vietnam; Food and Agriculture Organization of the United Nations (FAO); the World Animal Health Organization (OIE); the World Bank; and the Responsible Aquaculture Foundation of the Global Aquaculture Alliance for their support of this research. We also thank P. Hoang, an undergraduate student at Nong Lam University at Ho Chi Minh City, for help in running the bioassays conducted in Vietnam. In addition to Lightner, the co-authors of the paper are Loc Tran, Linda Nunan , Rita M. Redman , Leone L. Mohney , Carlos R. Pantoja and Kevin Fitzsimmons
Posted on: Thu, 18 Jul 2013 02:33:59 +0000
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