Multiple infections of a new-type decapod hepanhamaparvovirus (DHPV) and Enterocytozoon hepatopenaei in Korea and DHPV infectivity in Penaeus vannamei

Abstract

Decapod hepanhamaparvovirus (DHPV) is a viral pathogen known to cause slow growth and reduced productivity in penaeid shrimp. In this study, a new type of suspected DHPV was detected in cultured Pacific white shrimp (Penaeus vannamei) collected from 14 farms in Korea, where growth retardation was observed. DHPV was detected in 98 of 113 collected shrimp (86.7%), and 26 of 30 collected pond water (86.7%). Overall, DHPV was detected in 14 farms (100%), and coinfection of DHPV and Enterocytozoon hepatopenaei (EHP) was observed in 10 out of 14 farms (71.4%). We sequenced the presumptive viral DNA fragment at the junction of the genes encoding the NS2 and NS1 proteins of DHPV, and the nucleotide and deduced amino acid sequences which showed less than 89% and 86% identity, respectively to those of other DHPVs available in GenBank. Similarly, comparisons of the sequenced VP region of the DHPV from P. vannamei with those of other DHPVs indicated that the nucleotide and deduced amino acid sequences showed less than 79% and 83% identity, respectively. Phylogenetic analyses based on comparisons of the two DHPV fragments indicated that the newly detected DHPV in P. vannamei can be clearly differentiated from the DHPVs currently available in GenBank. Using a laboratory bioassay, the potential risk of DHPV transmission was examined by feeding virus-infected shrimp tissue to healthy P. vannamei, and potential DHPV infection was confirmed within 7 days based on PCR analysis and histopathological examination. The emergence of a new type of DHPV and its potential coinfection with EHP would have a significant impact on the global shrimp industry, and consequently, the presence of this virus in cultured shrimp as well as in the rearing pond water should be closely monitored to control its potential spread.