Risk factors associated with acute hepatopancreatic necrosis disease (AHPND) outbreak in the Mekong delta, Vietnam

Abstract

The Vietnamese shrimp farming industry has experienced massive production losses due to Acute Hepatopancreatic Necrosis Disease (AHPND) caused by Vibrio parahaemolyticus (VpAHPND) since 2011. The objective of this study was to identify factors associated with AHPND occurrence on shrimp farms in the Mekong Delta in Viet Nam. A retrospective crosssectional study was carried out on shrimp farms in four districts in the Mekong Delta area, Viet Nam from January 2012 to May 2013. Data were collected from 1920 ponds belonging to 1195 farms. Factors related to farm characteristics, farm management, pond and water preparation and management, feed management, postlarval (PL) shrimp, and stock management were evaluated. Multivariable logistic regression analysis was used to determine factors affecting the occurrence of AHPND at the pond and farm levels. The following characteristics were identified as significant farm-level risk factors: (i) having a larger culture area in terms of hectarage, (ii) using the sun-dried sediment method for cleaning pond bottom during the pond preparation process, and (iii) being sited close to other farms using the same AHPND-affected water source. Ponds with the following features were associated with increased risk of AHPND occurrence: (i) water depth of 1.2 m or less, (ii) extremely change of weather events occurring during the first 35 days of culture (DOC) or until the first signs of AHPND, and (iii) use of fertilizers and probiotics for water treatment. Moreover, ponds that were supplied with PL from some specific hatcheries were more likely to be infected with AHPND than were others. On the other hand, the risk of AHPND occurring was reduced in ponds that used minerals and algaecide for water treatment.