Analysis of variable genomic loci in white spot syndrome virus to predict its origins in Procambarus clarkii crayfish farmed in China

Advances on genomes studies of large DNA viruses in aquaculture: A minireview

Genomic studies of viral diseases in aquaculture have received more and more attention with the growth of the aquaculture industry, especially the emerging and re-emerging viruses whose genome could contain recombination, mutation, insertion, and so on, and may lead to more severe diseases and more widespread infections in aquaculture animals. The present review is focused on aquaculture viruses, which is belonged to two clades, Varidnaviria and Duplodnaviria, and one class Naldaviricetes, and respectively three families: Iridoviridae (ranaviruses), Alloherpesviridae (fish herpesviruses), and Nimaviridae (whispoviruses). The viruses possessed DNA genomes nearly or larger than 100 kbp with gene numbers more than 100 and were considered large DNA viruses. Genome analysis and experimental investigation have identified several genes involved in genome replication, transcription, and virus-host interactions. In addition, some genes involved in virus genetic variation or specificity were also discussed. A summary of these advances would provide reference to future discovery and research on emerging or re-emerging aquaculture viruses.

The effect of white spot syndrome virus (WSSV) envelope protein VP28 on innate immunity and resistance to white spot syndrome virus in Cherax quadricarinatus

VP28 is the most abundant membrane protein of WSSV, and the recombinant protein VP28 (VP26 or VP24) was constructed for the immune protection experiment in this study. Crayfish were immunized by intramuscular injection of recombinant protein V28 (VP26 or VP24) at a dose of 2 μg/g. The survival rate of crayfish immunized by VP28 showed a higher value than by VP26 or VP24 after WSSV challenge. Compared with the WSSV-positive control group, the VP28-immunized group could inhibit the replication of WSSV in crayfish, increasing the survival rate of crayfish to 66.67% after WSSV infection. The results of gene expression showed that VP28 treatment could enhance the expression of immune genes, mainly JAK and STAT genes. VP28 treatment also enhanced total hemocyte counts and enzyme activities including PO, SOD, and CAT in crayfish. VP28 treatment reduced the apoptosis of hemocytes in crayfish, as well as after WSSV infection. In conclusion, VP28 treatment can enhance the innate immunity of crayfish and has a significant effect on resistance to WSSV, and can be used as a preventive tool.

Bootstrapping random forest and CHAID for prediction of white spot disease among shrimp farmers

Technology is playing an important role is healthcare particularly as it relates to disease prevention and detection. This is evident in the COVID-19 era as different technologies were deployed to test, detect and track patients and ensure COVID-19 protocol compliance. The White Spot Disease (WSD) is a very contagious disease caused by virus. It is widespread among shrimp farmers due to its mode of transmission and source. Considering the growing concern about the severity of the disease, this study provides a predictive model for diagnosis and detection of WSD among shrimp farmers using visualization and machine learning algorithms. The study made use of dataset from Mendeley repository. Machine learning algorithms; Random Forest classification and CHAID were applied for the study, while Python was used for implementation of algorithms and for visualization of results. The results achieved showed high prediction accuracy (98.28%) which is an indication of the suitability of the model for accurate prediction of the disease. The study would add to growing knowledge about use of technology to manage White Spot Disease among shrimp farmers and ensure real-time prediction during and post COVID-19.

Experimental inoculation of oriental river prawn Macrobrachium nipponense with white spot syndrome virus (WSSV)

The oriental river prawn Macrobrachium nipponense is an economically important species that is widely farmed in China. White spot syndrome virus (WSSV) is one of the most devastating pathogens of the cultured shrimp Litopenaeus vannamei, responsible for massive loss of its commercial products worldwide. We investigated the infectivity and pathogenicity of WSSV in adult M. nipponense using standardized conditions for L. vannamei. The median lethal dose of WSSV in adult M. nipponense was 103.84±0.06 copies g-1, which was about 1000-fold higher than in L. vannamei (100.59±0.22 copies g-1). WSSV was detected by 2-step PCR in the gills, hepatopancreas, muscle, stomach, heart, gut, nerve, integument, pereopod, eyestalk, testis, and ovary of experimentally infected dead M. nipponense. Lesions were observed histologically following WSSV injection, showing basophilic intranuclear inclusion bodies in the hepatopancreas and subsequently in the gills. The clearance of WSSV was observed in hepatopancreas and gills at 48 and 96 h post-inoculation, respectively. No histological lesions were detected in muscle from 0-96 h post-injection. The results show that the oriental river prawn M. nipponense can be infected by WSSV and the infections are self limiting over time; therefore, M. nipponense may serve as a useful model for studying resistance to WSSV.

The cDNA Sequence of Two Hemocyanin Subunits from Red Swamp Crayfish Procambarus clarkii and their Responses to White Spot Syndrome Virus Infection

Hemocyanin, the respiratory protein of crustaceans, participates in the innate immune defense in these organisms. We cloned two hemocyanin subunit genes (PcHc1 and PcHc2), by using a degenerate primer PCR and rapid amplification of cDNA ends (RACE) approach, from the hepatopancreas of red swamp crayfish Procambarus clarkii. The transcripts of these two subunits were only detected in the hepatopancreas by reverse transcriptase quantitative PCR (RT-qPCR) analysis. The neighbor-joining and maximum parsimony phylogenetic analyses indicated that PcHc2 associated with a clade belong to the α-type hemocyanins and PcHc1 associated with another clade belonging to the β-type hemocyanins. The data obtained from the RT-qPCR indicated that the mRNA expression levels of these subunit genes followed almost the same regulation pattern in the crayfish challenged with white spot syndrome virus (WSSV). The fluctuation of mRNA expression levels of these two subunits after the WSSV challenge indicated that both of them may participate in the antiviral immune response of crayfish. Received April 12, 2015; accepted November 22, 2015.

Global Introductions of Crayfishes: Evaluating the Impact of Species Invasions on Ecosystem Services

Impacts of nonindigenous crayfishes on ecosystem services exemplify the mixture of positive and negative effects of intentionally introduced species. Global introductions for aquaculture and ornamental purposes have begun to homogenize naturally disjunct global distributions of crayfish families. Negative impacts include the loss of provisioning (e.g., reductions in edible native species, reproductive interference or hybridization with native crayfishes), regulatory (e.g., lethal disease spread, increased costs to agriculture and water management), supporting (e.g., large changes in ecological communities), and cultural (e.g., loss of festivals celebrating native crayfish) services. Where quantification of impacts exists (e.g., Procambarus clarkii and Pacifastacus leniusculus in Europe), regulations now prohibit introduction and spread of crayfishes, indicating that losses of ecosystem services have outweighed gains. Recent research advances such as predicting invasiveness, predicting spread, improved detection and control, and bioeconomic analysis to increase cost-effectiveness of management could be employed to reduce future losses of ecosystem services.