Protection from yellow head virus (YHV) infection in Penaeus vannamei pre-infected with Taura syndrome virus (TSV)

Coinfection with Yellow Head Virus Genotype 8 (YHV-8) and Oriental Wenrivirus 1 (OWV1) in Wild Penaeus chinensis from the Yellow Sea

At present, there are few studies on the epidemiology of diseases in wild Chinese white shrimp Penaeus chinensis. In order to enrich the epidemiological information of the World Organisation for Animal Health (WOAH)-listed and emerging diseases in wild P. chinensis, we collected a total of 37 wild P. chinensis from the Yellow Sea in the past three years and carried out molecular detection tests for eleven shrimp pathogens. The results showed that infectious hypodermal and hematopoietic necrosis virus (IHHNV), Decapod iridescent virus 1 (DIV1), yellow head virus genotype 8 (YHV-8), and oriental wenrivirus 1 (OWV1) could be detected in collected wild P. chinensis. Among them, the coexistence of IHHNV and DIV1 was confirmed using qPCR, PCR, and sequence analysis with pooled samples. The infection with YHV-8 and OWV1 in shrimp was studied using molecular diagnosis, phylogenetic analysis, and transmission electron microscopy. It is worth highlighting that this study revealed the high prevalence of coinfection with YHV-8 and OWV1 in wild P. chinensis populations and the transmission risk of these viruses between the wild and farmed P. chinensis populations. This study enriches the epidemiological information of WOAH-listed and emerging diseases in wild P. chinensis in the Yellow Sea and raises concerns about biosecurity issues related to wild shrimp resources.

Viral Shrimp Diseases Listed by the OIE: A Review

Shrimp is one of the most valuable aquaculture species globally, and the most internationally traded seafood product. Consequently, shrimp aquaculture practices have received increasing attention due to their high value and levels of demand, and this has contributed to economic growth in many developing countries. The global production of shrimp reached approximately 6.5 million t in 2019 and the shrimp aquaculture industry has consequently become a large-scale operation. However, the expansion of shrimp aquaculture has also been accompanied by various disease outbreaks, leading to large losses in shrimp production. Among the diseases, there are various viral diseases which can cause serious damage when compared to bacterial and fungi-based illness. In addition, new viral diseases occur rapidly, and existing diseases can evolve into new types. To address this, the review presented here will provide information on the DNA and RNA of shrimp viral diseases that have been designated by the World Organization for Animal Health and identify the latest shrimp disease trends.

Mini Review: Virus Interference: History, Types and Occurrence in Crustaceans

Virus interference is a phenomenon in which two viruses interact within a host, affecting the outcome of infection of at least one of such viruses. The effect of this event was first observed in the XVIII century and it was first recorded even before virology was recognized as a distinct science from microbiology. Studies on virus interference were mostly done in the decades between 1930 and 1960 in viruses infecting bacteria and different vertebrates. The systems included in vivo experiments and later, more refined assays were done using tissue and cell cultures. Many viruses involved in interference are pathogenic to humans or to economically important animals. Thus the phenomenon may be relevant to medicine and to animal production due to the possibility to use it as alternative to chemical therapies against virus infections to reduce the severity of disease/mortality caused by a superinfecting virus. Virus interference is defined as the host resistance to a superinfection caused by a pathogenic virus causing obvious signs of disease and/or mortality due to the action of an interfering virus abrogating the replication of the former virus. Different degrees of inhibition of the superinfecting virus can occur. Due to the emergence of novel pathogenic viruses in recent years, virus interference has recently been revisited using different pathogens and hosts, including commercially important farmed aquatic species. Here, some highly pathogenic viruses affecting farmed crustaceans can be affected by interference with other viruses. This review presents data on the history of virus interference in hosts including bacteria and animals, with emphasis on the known cases of virus interference in crustacean hosts. Life Science Identifiers (LSIDs) Escherichia coli [(Migula 1895) Castellani & Chalmers 1919] Aedes albopictus (Skuse 1894) Liocarcinus depurator (Linnaeus 1758): urn:lsid:marinespecies.org:taxname:107387 Penaeus duorarum (Burkenroad 1939): urn:lsid:marinespecies.org:taxname:158334 Carcinus maenas (Linnaeus 1758): urn:lsid:marinespecies.org:taxname:107381 Macrobrachium rosenbergii (De Man 1879): urn:lsid:marinespecies.org:taxname:220137 Penaeus vannamei (Boone 1931): urn:lsid:zoobank.org:pub:C30A0A50-E309-4E24-851D-01CF94D97F23 Penaeus monodon (Fabricius 1798): urn:lsid:zoobank.org:act:3DD50D8B-01C2-48A7-B80D-9D9DD2E6F7AD Penaeus stylirostris (Stimpson 1874): urn:lsid:marinespecies.org:taxname:584982.

Novel infectious myonecrosis virus (IMNV) genotypes associated with disease outbreaks on Penaeus vannamei shrimp farms in Indonesia

Infectious myonecrosis virus (IMNV) is one of the most pathogenic viruses that affect Penaeus vannamei shrimp. In 2018, IMNV was reported in grow-out ponds of P. vannamei in Situbondo, Indonesia. Diseased animals displayed clinical signs of infectious myonecrosis (IMN) characterized by white discoloration of skeletal muscle. Histopathology of affected shrimp revealed lesions that are pathognomonic of IMNV infection. The major capsid protein (MCP) gene was amplified and sequenced from representative samples showing IMN pathology. Multiple alignment of predicted amino acid sequences of the MCP gene with known IMNV genotypes in the GenBank database revealed three unique genotypes, SB-A, SB-B and SB-C,in Situbondo samples. The number of amino acid changes in SB-A, SB-B and SB-C compared to known IMNV genotypes ranged from 7-710, including the isolate SB-B, which contains deletion of 622 aa. A phylogenetic analysis using homologous sequences from Brazil and Indonesia showed that these three isolates represent new IMNV genotypes.

First report of acute hepatopancreatic necrosis disease (AHPND) occurring in the USA

In June 2017, mass mortalities were reported at whiteleg shrimp Penaeus vannamei farms in Texas, USA. PCR testing for OIE-listed and non-listed pathogens detected the pirA and pirB toxin genes associated with acute hepatopancreatic necrosis disease (AHPND). DNA sequence analyses of cloned pirA and pirB genes showed them to be identical to those detected in other AHPND-causing Vibrio sp. Amplicons generated using PCR tests targeted to the toxR gene showed the Pir toxin genes to be associated with a V. parahaemolyticus type more similar to a genotype found in Mexico compared to that found in Asia. Histology detected masses of bacteria and hemocytic infiltrations as well as extensive necrosis and sloughing of epithelial cells in hepatopancreatic tubules pathognomonic of AHPND. The data support AHPND as the cause of the mortalities. Given that US companies produce shrimp broodstock for farms in Asia and Latin America, the further spread of AHPND in the USA needs to be prevented to avoid serious economic consequences to these industries.

Nidoviruses of Fish and Crustaceans

Viruses with diverse virion architectures demarcated into four families in the order Nidovirales have been discovered in vertebrate mammalian and fish species, as well as in invertebrate crustacean and mosquito species. The order is unified by nidoviruses sharing intermediate (12.7 kb) to very long (31.7 kb) (+) ssRNA genomes, each possessing a long 5′-terminal gene encoding overlapping ORF1a and ORF1b reading frames that contain a diversity of functionally related enzymes and that are translated in toto using a −1 ribosomal frameshift mechanism, as well as by semiconserved strategies for transcribing a nested set of 3′-coterminal subgenomic mRNAs that translate the viral proteins. The nidovirus that is most important to an aquaculture species is yellow head virus (YHV), which causes disease in shrimp farmed throughout the Eastern Hemisphere and is classified in the genus Okavirus, family Roniviridae. Fathead minnow nidovirus, genus Bafinivirus, subfamily Torovirinae, family Coronaviridae, also causes disease in minnows grown for the baitfish industry in the United States. Virions similar in morphology to okaviruses and bafiniviruses have also been detected in several crab species. Of these, however, only Eriocheir sinensis ronivirus, which causes disease in the Chinese mitten crab, an important freshwater aquaculture species in China, has been shown to possess a ~22 kb ssRNA genome that supports its being a nidovirus, but its taxonomic classification awaits genome sequence analysis. This chapter provides an overview of the structure, replication and biology of these viruses with a particular focus on YHV disease characteristics, diagnostic methods and disease prevention strategies.