Impact of farm management on expression of early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) on penaeid shrimp farms in Thailand V Boonyawiwat 1,2 , T Patanasatienkul 2 , J Kasornchandra 3 , C Poolkhet 1 , S Yaemkasem 4 , L Hammell 2 and J Davidson 2 1 Faculty of Veterinary Medicine, Kasetsart University, Kamphangsaen, Nakhon Pathom, Thailand 2 Department of Health Management, Atlantic Veterinary College, Centre for Veterinary and Epidemiological Research, University of Prince Edward Island, Charlottetown, PE, Canada 3 Expert Bureau Division, Department of Fisheries, Chatuchak, Bangkok, Thailand 4 Rayong Coastal Aquaculture Research and Development Center, Department of Fisheries, Mueang, Rayong, Thailand Abstract Asian shrimp farming industry has experienced massive production losses due to a disease caused by toxins of Vibrio bacteria, known as early mortality syndrome/acute hepatopancreatic necrosis disease (EMS/AHPND) for the last 5 years. The disease can cause up to 100% cumulative pond mortality within a week. The objective of this study was to identify factors associated with AHPND occurrence on shrimp farms. A case–control study was carried out on shrimp farms in four provinces of Thailand. Factors related to farm characteristics, farm man- agement, pond and water preparation, feed man- agement, post-larvae (PL) shrimp and stock management were evaluated. Multivariable logistic regression analysis identified factors affecting AHPND occurrence at the pond level. Chlorine treatment, reservoir availability, use of predator fish in the water preparation, culture of multiple shrimp species in one farm and increased PL stocking den- sity contributed to an increased risk of AHPND infection, while delayed first day of feeding, poly- culture and water ageing were likely to promote outbreak protection. Additionally, the source of PL was found to be associated with AHPND occur- rence in shrimp ponds, which requires further study at the hatchery level. Identification of these factors will facilitate the development of effective control strategies for AHPND on shrimp farms. Keywords: acute hepatopancreatic necrosis disease, early mortality syndrome, farm management, Penaeus vannamei, Vibrio parahaemolyticus. Introduction Farmed shrimp account for 57% of the total shrimp consumed globally (7.9 million tons), with whiteleg shrimp (Penaeus vannamei Boone, 1931) being the main cultured species (74% of total cul- tured shrimp) (FAO 2015). The major producers are China, Vietnam and Thailand (FAO 2010). Although global shrimp production has increased from approximately one million tons in 2000 to four million tons in 2011, the 2015 level is expected to be 15% below that of 2011 due to dis- ease outbreaks causing significant production losses (Jory 2014). Early mortality syndrome, more precisely known as acute hepatopancreatic necrosis disease (AHPND), has been attributed as the cause of devastating losses in the shrimp aquaculture indus- try of South-East Asia over the past 5 years. The disease was first reported in China in 2010, fol- lowed by Vietnam and Malaysia in early 2011 (Lightner et al. 2012) and Thailand in late 2011 Correspondence T Patanasatienkul, Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, Charlottetown PE C1A 4P3 Canada (e-mail: thitiwan.patanasatienkul@gmail.com) 1 Ó 2016 John Wiley & Sons Ltd Journal of Fish Diseases 2016 doi:10.1111/jfd.12545