Detection of the etiologic agent of necrotizing hepatopancreatitis in cultured Penaeus vannamei from Texas and Peru by polymerase chain reaction

Necrotizing hepatopancreatitis (NHP) is a severe bacterial disease that was previously identified solely in cultured Penaeus vannamei, the Pacific white shrimp, from Texas (USA). In January 1993, a disease with similar clinical and histopathologic features to NHP was diagnosed in P. vannamei cultured in Peru. Oligonucleotide primers derived from variable regions V5, V8 and V9 of the 16S ribosomal RNA gene sequence enabled polymerase chain reaction (PCR) confirmation of the diagnosis of NHP in both Texan and Peruvian shrimp. The PCR amplification products from the clinical specimens were compared to the PCR amplification product obtained from a sucrose-gradient purified sample of bacteria that was previously used to reproduce NHP. In this study, fingerprinting by restriction fragment length polymorphism (RFLP) analysis of the PCR products was used to compare the isolates. Results indicate that hepatopancreatic lesions are caused by the same bacterium in both Texas and Peru. Negative results were obtained from uninfected shrimp and shrimp infected with Vibrio spp., as well as DNA extracted from Brucella abortus, Ehrlichia risticii, Salmonella enteritidis, Agrobacterium tumefaciens and Streptococcus criae.