Different reactions obtained using the same DNA detection reagents for Thai and Korean hepatopancreatic parvovirus of penaeid shrimp

Hepatopancreatic parvovirus (HPV) can cause stunted growth and death in pen aeid shrimp including Penaeus monodon. We used PCR primers and a commercial DNA probe designed from HPV of Penaeus chinensis (HPV-chin) to examine HPV -infected Thai P. monodon (HPVmon). We found that the PCR primers produced a 732 bp DNA amplicon rather than the 350 bp amplicon obtained with HPVchin template and that the DNA probe gave weak to variable in situ DNA hybridiz ation results, In addition, hybridization to PCR products from HPVmon was w eak compared with hybridization with PCR products from HPVchin. By contrast , the 732 bp amplicon hybridized strongly with HPVmon-infected cells by in situ hybridization but not with uninfected shrimp tissue or other shrimp vi ruses, thus confirming its origin from HPVmon. Cloning, sequencing and anal ysis of the 732 bp amplicon showed that 696 bp (excluding the primer sequen ces) contained 47 % GC content and had only 78 % homology to 701 aligned ba ses from a 3350 bp DNA fragment of HPVchin from GenBank. These results expl ain why the reagents based on HPVchin gave a different PCR product and weak hybridization results with HPVmon, and they show that multiple primers or degenerate primers may be necessary for general detection of HPV varieties. Together with previously published information on the estimated total geno me sizes for HPVchin (approximately 4 kb) and HPVmon (approximately 6 kb), these data support the contention that HPVchin and HPVmon are different var ieties or species, in spite of their similar histopathology.