Biology subjects

Flegel, T. W.

Publications and source records attributed to Flegel, T. W..

3 recordsLinked to original sources

bioRxiv2020

Infectious myonecrosis virus (IMNV) and decapod iridescent virus 1 (DIV1) detected in Penaeus monodonfrom the Indian Ocean

Infectious myonecrosis virus (IMNV) was first discovered in the Americas in 2004 as a new lethal pathogen of cultivated whiteleg shrimp Penaeus vannamei, but infections were not lethal for the giant tiger shrimp Penaeus monodon. In 2007, it was reported in diseased P. vannamei cultivated in Indonesia but, until recently, not from other countries in Asia. Decapod iridescent virus (DIV1) was first reported from China in 2016 and is lethal for the crayfish Cherax quadricarinatus and Procambarus clarkii, for the penaeid shrimp P. vannamei and P. chinensis and for the palaemonid shrimp Macrobrachium rosenbergii and Exopalaemon carinicauda. It has not yet been reported from other Asian countries. Here we describe the occurrence of positive test results for IMNV and DIV1 using polymerase chain reaction (PCR) technology during screening of grossly normal, broodstock-size, wild P. monodon captured from the Indian Ocean and held in a biosecurity facility for screening. Amplicons for each virus were obtained from two widely separated targets in the relevant viral genomes listed at GenBank, and sequencing revealed 99-100% identity to the targets for each virus. Based on these results, the captured specimens were destroyed. The results raised the possibility that grossly normal, captured P. monodon might serve as potential vehicles for introduction of IMNV and/or DIV1 to shrimp hatcheries and farms. Thus, we recommend that appropriate precautions be taken to avoid this possibility.

zoology↗

bioRxiv2020

Potential universal PCR method to detect decapod hepanhamaparvovirus (DHPV) in crustaceans

Parvoviruses that infect the hepatopancreas (HP) of the penaeid shrimp Penaeus chinensis, P. monodon, and P. merquiensis were previously called hepatopancreatic parvoviruses (HPV). They are now classified in the family Parvoviridae, sub-family Hamaparvovirinae as members of the same genus called Hepanhamaparvovirus and referred to as decapod hepanhamaparvovirus, designated here as DHPV. However, a virus that causes similar lesions in the HP of the giant river prawn Macrobrachium rosenbergii resembles hepanhamaparvoviruses by microscopy and histochemistry. Unfortunately, no genome information is yet available and PCR detection methods that work for DHPV in P. monodon do not work with M. rosenbergii. For hatchery samples of M. rosenbergii in Thailand with DHPV-like lesions, we hypothesized it might be possible to design primer pairs from 8 full DHPV genome sequences at GenBank for use in PCR detection of DHPV in M. rosenbergii. Using this strategy, we successfully designed a new set of primers and a PCR protocol called the DHPV-U method that gave an amplicon with DNA extracts from larvae of M. rosenberigii samples that showed DHPV-like lesions, while extracts from normal larvae gave none. DNA extracts from P. monodon infected with DHPV also gave amplicons. At the same time, the normal PCR method for DHPV in P. monodon gave no amplicon with the M. rosenbergii DNA extracts. The DHPV-U amplicons from P. monodon and M. rosenbergii shared 99% sequence identity, and in situ hybridization (ISH) assays using the DIG-labeled amplicon gave positive histochemical results in the HP tissue of both P. monodon and M. rosenbergii. The DHPV-U method is now being used in Thailand for detection of DHPV in both P. monodon and M. rosenbergii. Overall, the results support the proposal that the HP virus in M. rosenbergii is also a hepanhamaparvovirus. Based on 100% sequence identity of the target region in the currently published DHPV sequences at GenBank, the DHPV-U method may also work for detection of other DHPV isolates.

molecular biology↗

bioRxiv2020

Full genome characterization of Laem Singh virus (LSNV) in shrimp Penaeus monodon

Laem Singh virus (LSNV) was discovered in 2006 and proposed as a necessary but insufficient cause of retarded growth in the giant tiger shrimp Penaeus monodon. Its closest relatives were plant viruses including an unassigned Sobemovirus and viruses in the family Luteoviridae. During succeeding years, attempts to obtain the full LSNV genome sequence by genome walking failed. However, recent publication of the full sequence of Wenzhou shrimp virus 9 (WZSV 9) at GenBank revealed that LSNV sequences in our database shared 99% sequence identity with it. Thus, we hypothesized that LSNV and WZSV 9 were different isolates of the same virus species. Here we confirm that hypothesis by cloning and sequencing of the full genome of LSNV from P. monodon and by showing that it consists of two fragments each with 99% identity to the matching fragments of WZSV.

microbiology↗