FIRST REPORT OF THE PRESENCE OF ACUTE HEPATOPANCREATIC NECROSIS DISEASE (AHPND) IN TEXAS, USA

A disease outbreak occurred in shrimp farms cultivating Penaeus vannamei shrimp in Texas, USA that caused large-scale mortalities during June 2017. Shrimp samples originated from these farms were tested in Aquaculture Pathology Laboratory in The University of Arizona, Tucson, Arizona. Duplex polymerase chain reaction (PCR) performed using DNA isolated from hepatopancreas tissue and OIE-approved primer sets used to detect acute hepatopancreatic necrosis disease (AHPND) causing Vibrio sp carrying binary toxin genes (pir A and pir B) provided positive results. The presence of DNA containing toxin gene in the samples were further confirmed by another set of OIE-approved primers, AP4. Subsequently PCR was carried out to identify the presence of Vibrio species in hepatopancreas tissue. The results showed that the DNA samples isolated from P. vannamei hepatopancreas tissue represents V. parahaemolyticus. The PCR-based genotyping revealed that the V. parahaemolyticus present in the P. vannamei Texas samples represent Mexican genotype, and not Asian genotype. The full-length of the binary toxin genes, pir A and pir B, were amplified by PCR and sequence analysis performed to determine the sequence similarity with known homologous sequences in the GenBank database. Histopathology of P. vannamei shrimp originated from the Texas farm revealed characteristic lesions pathognomonic of AHPND. Our results showed P. vannamei shrimp originated from Texas farms experiencing large-scale mortalities contained V. parahaemolyticus causing AHPND. To our knowledge, this is the first report of the presence of AHPND causing V. parahaemolyticus in the US.