This study was supported by a research grant from National Science and Technology Development Agency (NSTDA), Thailand (P-18-52583). Liseth Lucero Huamancha Pulido acknowledges the financial support from Cienciactiva – Concytec (management agreement N°230-2015-FONDECYT) - Master in Aquaculture Health of Cayetano Heredia Peruvian University. The authors would like to thank P. Meenium and C. Techatanakitarnan for their technical assistance.

Acute hepatopancreatic necrosis disease (AHPND) is a newly emerging disease of penaeid shrimps caused by a unique strain of Vibrio species that carries a plasmid harboring PirABVp-binary toxin gene. Since the first outbreak in 2009, the diseases have been reported in a number of countries in Asia, America, and Latin America. In the present study, we obtained 51 bacterial isolates recovered from five AHPND suspected shrimp farms in South America for PCR diagnosis using AP4 nested PCR method. There were 3/51 isolates (34, 36 and 43) from two farms which tested positive by AP4 primers targeting PirABVp toxin genes. The detection results were also confirmed by duplex pirABVp PCR assay. Subsequently, integrity of full length pirABVp genes in the three positive isolates was revealed by sequencing analysis. Bacterial species identification by ldh-specific PCR combined with multilocus sequencing...