Incidence of mud crab reovirus (MCRV) outbreak in polyculture ponds of Andhra Pradesh, south east coast of India

Reovirus designated as Mud crab reovirus (MCRV) is associated with the mass mortalities of mud crabs resulting in significant economic loss to crab and shrimp-mud crab polyculture farmers in the Nagayalanka, Krishna district, Andhra Pradesh. The 100 % chronic mass mortalities have been attributed to the outbreak of Mud crab reovirus (MCRV) in the polyculture farms. The moribund crabs showed autotomy, discoloration of carapace, loss of appetite, slow movement and loose gills. Histopathological observations of the infected mud crabs showed an atrophied hepatopancreas, complete degeneration of tissues along with viral inclusions in hepatopancreas, gills and muscles. Further analysis using Transmission electron microscopy (TEM), showed that the viral particles had a diameter of 70 nm and exhibited a non-enveloped, icosahedral shape arranged in a crystalline manner. The virus mainly infects the connective tissue of hepatopancreas, gills, muscle and develops in the cytoplasm. RT-PCR reconfirmed the presence of reovirus in the hepatopancreas of spontaneously infected mud crab Scylla serrata. The current study shows the importance of monitoring the MCRV prevalence in polyculture farms to minimize its spread and precautionary measures can be taken by screening the brooders from the crab hatchery and stocking of wild crabs without screening should be avoided in order to prevent MCRV outbreak.

Virome Analysis of Signal Crayfish (Pacifastacus leniusculus) along Its Invasion Range Reveals Diverse and Divergent RNA Viruses

Crayfish are a keystone species of freshwater ecosystems and a successful invasive species. However, their pathogens, including viruses, remain understudied. The aim of this study was to analyze the virome of the invasive signal crayfish (Pacifastacus leniusculus) and to elucidate the potential differences in viral composition and abundance along its invasion range in the Korana River, Croatia. By the high-throughput sequencing of ribosomal RNA, depleted total RNA isolated from the crayfish hepatopancreas, and subsequent sequence data analysis, we identified novel and divergent RNA viruses, including signal crayfish-associated reo-like, hepe-like, toti-like, and picorna-like viruses, phylogenetically related to viruses previously associated with crustacean hosts. The patterns of reads abundance and calculated nucleotide diversities of the detected viral sequences varied along the invasion range. This could indicate the possible influence of different factors and processes on signal crayfish virome composition: e.g., the differences in signal crayfish population density, the non-random dispersal of host individuals from the core to the invasion fronts, and the transfer of viruses from the native co-occurring and phylogenetically related crayfish species. The study reveals a high, previously undiscovered diversity of divergent RNA viruses associated with signal crayfish, and sets foundations for understanding the potential risk of virus transmissions as a result of this invader’s dispersal.

The T cell factor, pangolin, from Litopenaeus vannamei play a positive role in the immune responses against white spot syndrome virus infection

As a downstream interactor of β-catenin, Pangolin which is the homologous protein of the T cell factor/lymphoid enhancer factor (TCF/LEF) in vertebrates is less understood in the research field of immunity. In this study, two isoforms of Litopenaeus vannamei Pangolin (LvPangolin1 and LvPangolin2) were identified. Phylogenetic tree analysis revealed that all of the Pangolin proteins from invertebrates were represented the same lineage. The mRNA expression profiles of the LvPangolin1 and LvPangolin2 genes differed across different tissues. The expression of LvPangolin1 and the amount of LvPangolin1and LvPangolin2 combined (LvPangolinComb) were significantly increased in the haemocyte, intestine and gill but reduced in the hepatopancreas after white spot syndrome virus (WSSV) challenge. The inhibition of LvPangolin1 but not LvPangolinComb significantly reduced the survival rates of L. vannamei after WSSV infection, while significantly higher WSSV viral loads in both LvPangolin1-inhibited and LvPangolinComb-inhibited L. vannamei were observed. Knockdown of LvPangolin by RNAi could distinctly decrease the expression of antimicrobial peptide (AMP) genes and their related transcription factors. All of these results indicate that LvPangolin plays a positive role in the response to WSSV infection and that this may be mediated through regulating the immune signalling pathways which control the expression of AMPs with antiviral abilities.

Oral immunization with recombinant Lactobacillus casei displayed AHA1-CK6 and VP2 induces protection against infectious pancreatic necrosis in rainbow trout (Oncorhynchus mykiss)

Infectious pancreatic necrosis virus (IPNV) primarily infects larvae and young salmonid with serious economic losses, which causes haemorrhage and putrescence of hepatopancreas. To develop a more effective oral vaccine against IPNV infection, the aeromonas hydrophila adhesion (AHA1) gene was used as a targeting molecule for intestinal epithelial cells. A genetically engineered Lactobacillus casei (pPG-612-AHA1-CK6-VP2/L. casei 393) was constructed to express the AHA1-CK6-VP2 fusion protein. The expression of interest protein was confirmed by western blotting and the immunogenicity of pPG-612-AHA1-CK6-VP2/L. casei 393 was evaluated. And the results showed that more pPG-612-AHA1-CK6-VP2/L. casei 393 were found in the intestinal mucosal surface of the immunized group. The Lactobacillus-derived AHA1-CK6-VP2 fusion protein could induce the production of serum IgM and skin mucus IgT specific for IPNV with neutralizing activity in rainbow trouts. The levels of IL-1β, IL-8 and TNF-α isolated from the lymphocytes stimulated by AHA1-CK6-EGFP produced were significantly higher than EGFP group. For transcription levels of IL-1β, IL-8, CK6, MHC-II, Mx and TNF-1α in the spleen, the result indicated that the adhesion and target chemokine recruit more immune cells to induce cellular immunity. The level of IPNV in the immunized group of pPG-612-AHA1-CK6-VP2/L. casei 393 was significantly lower than that in the control groups. These data indicated that the adhesion and target chemokine could enhance antigen delivery efficiency, which provides a valuable strategy for the development of IPNV recombination Lactobacillus casei oral vaccine in the future.

The red swamp crayfish, Procambarus clarkii cathepsin C, participates in the innate immune response to the viral and bacterial pathogens

The cathepsin C, a lysosomal cysteine protease, involves the modulation of immune and inflammatory responses in living organisms. However, the knowledge on cathepsin C in red swamp crayfish (Procambarus clarkii), a freshwater crustacean with economic values, remained unclear. In the present study, we provide identification and molecular characterization of cathepsin C from P. clarkii. (Hereafter Pc-cathepsin C). The Pc-cathepsin C cDNA contained a 1356 bp open reading frame that encoded a protein of 451 amino acid residues. The deduced amino acid sequence comprised of cathepsin C exclusion domain and pept_C1 domain, and also catalytic residues (Cys²⁴⁸, His³⁹⁵ and Asn⁴¹⁷). Analysis of the transcriptional patterns of the Pc-cathepsin C gene revealed that it was broadly distributed in various tissues of P. clarkii, and it was more abundant in the hepatopancreas and gut. Following a challenge with viral and bacterial pathogen-associated molecular patterns, the expression of Pc-cathepsin C was strongly enhanced at different time points. The knockdown of Pc-cathepsin C, altered the expression of immune-responsive genes, suggesting its immunoregulatory role in P. clarkii. This study has identified and provided the immunoregulatory function of Pc-cathepsin C, which will contribute to further investigation of the molecular mechanism of cathepsin C in crustaceans.

Transcriptome analysis of Procambarus clarkii infected with infectious hypodermal and haematopoietic necrosis virus

Infectious hypodermal and haematopoietic necrosis virus (IHHNV) is a major viral pathogen in cultured penaeid shrimp. IHHNV has many hosts, mainly including crustaceans. It has recently been reported that Procambarus clarkii can be infected by IHHNV. In the present study, we studied the hepatopancreas of P. clarkii by transcriptome high-throughput sequencing to analyze the response of P. clarkii to IHHNV infection. After de novo assembly, there were 400,340,760 clean reads. A total of 237 differentially expressed genes (DEGs) were obtained, including 77 significantly up-regulated unigenes and 160 significantly down-regulated ones. The expression levels of 12 immune-related DEGs were validated by qRT-PCR, substantiating the reliability of RNA-Seq results. The enrichment analysis of DEGs showed that the immune-related pathways were closely related to apoptosis and phagocytosis. Moreover, a large number of pathways related to metabolic function were down-regulated, suggesting that IHHNV infection might affect the growth of P. clarkii.

Silencing of HIF-1 in WSSV-infected white shrimp: Effect on viral load and antioxidant enzymes

Hypoxia inducible factor-1 (HIF-1) is a transcriptional factor that induces genes involved in glucose metabolism. HIF-1 is formed by a regulatory α-subunit (HIF-1α) and a constitutive β-subunit (HIF-1β). The white spot syndrome virus (WSSV) induces a shift in glucose metabolism and oxidative stress. HIF-1α is associated with the induction of metabolic changes in tissues of WSSV-infected shrimp. However, the contributions of HIF-1 to viral load and antioxidant responses in WSSV-infected shrimp have been not examined. In this study, the effect of HIF-1 silencing on viral load and the expression and activity of antioxidant enzymes (superoxide dismutase-SOD, glutathione S-transferase-GST, and catalase) along with oxidative damage (lipid peroxidation and protein carbonyl) in tissues of white shrimp infected with the WSSV were studied. The viral load increased in hepatopancreas and muscle after WSSV infection, and the accumulative mortality was of 100% at 72 h post-infection. The expression and activity of SOD, catalase, and GST decreased in each tissue evaluated after WSSV infection. Protein carbonyl concentrations increased in each tissue after WSSV infection, while lipid peroxidation increased in hepatopancreas, but not in muscle. Silencing of HIF-1α decreased the WSSV viral load in hepatopancreas and muscle of infected shrimp along with shrimp mortality. Silencing of HIF-1α ameliorated the antioxidant response in a tissue-specific manner, which translated to a decrease in oxidative damage. These results suggest that HIF-1 is essential for restoring the antioxidant response, which counters the oxidative injury associated with WSSV infection.

Presence of Penaeus monodon densovirus in the ovary of chronically infected P. monodon subadults

Shrimp infected with Penaeus monodon densovirus (PmoDNV) usually display no specific gross signs, but heavy infections can kill postlarvae and retard juvenile growth. In the present study, samples of hepatopancreas, feces, gonads and hemolymph were isolated from male and female P. monodon subadults chronically infected by PmoDNV. Each sample of hepatopancreas and gonad was divided into 2 parts: one for PmoDNV detection by polymerase chain reaction (PCR), and the other for routine histology and immunohistochemistry. The frequency of positive findings via PCR assays was 92% in the hepatopancreas, 57% in feces, 50% in ovary, 35% in hemolymph and 0% in the testis. Using the densitometric value (DV) of the specific band for PmoDNV relative to that of the β-actin gene as an index of the viral load in the samples, no significant differences were observed among sample types and sexes. Hematoxylin-eosin staining of infected hepatopancreas revealed typical PmoDNV inclusions in the nuclei of infected cells. The ovaries with high DV (>1) contained various types of inclusions along the row of the follicular cells or possibly in the connective tissue cells surrounding the oocytes. Using immunohistochemistry with specific probes to detect PmoDNV proteins, a positive reaction was observed in viral inclusions found in infected hepatopancreas and in ovaries with high DV, specifically in the ovarian capsule, hemolymph, oocytes and nuclear inclusions. These results suggest that the localization of PmoDNV in P. monodon is not confined to the hepatopancreas, but rather that the virus can also occur in the ovary; hence, trans-ovarian, vertical transmission of the virus is highly possible.

Transcriptome profiles of the clam Meretrix petechialis hepatopancreas in response to Vibrio infection

Microbial diseases have received much attention due to their enormous destruction of aquaculture, and Vibrio parahaemolyticus is one of the main pathogens that cause bacterial disease in the clam Meretrix petechialis. To better understand the molecular mechanisms of the immune response to Vibrio in M. petechialis, RNA-Seq was applied to explore global expression changes of hepatopancreas from this clam after Vibrio challenge. There were 199,318,966 clean reads obtained by Illumina sequencing, which were further assembled into 214,577 transcripts, and then 147,255 unigenes with an N50 of 1393 bp were identified. Gene ontology (GO) analysis revealed 21 biological process subcategories, 15 cellular component subcategories and 12 molecular function subcategories. A total of 8358 unigenes were mapped onto 267 biological signaling pathways by KEGG, among which there were 16 pathways related to the immune system. In total, 206 differentially expressed genes (DEGs) were identified, including 113 up-regulated unigenes and 93 down-regulated unigenes. In these DEGs, 96 DEGs were annotated in at least one database, accounting for 46.60% of all significant DEGs. To validate the transcriptome dataset, 15 DEGs were selected for real-time qPCR confirmation and the results showed that expression patterns of 13 genes (86.7%) agreed well with the RNA-Seq analysis. Fourteen of the 206 DEGs were annotated to be immune-related genes, and we examined the expression patterns of four immune-related DEGs using clams post immersion challenge. This study enriched the M. petechialis transcriptome database and provided insight into the immune response of M. petechialis against Vibrio infection.

Molecular and immune response characterizations of a novel AIF and cytochrome c in Litopenaeus vannamei defending against WSSV infection

Apoptosis inducing factor (AIF) and cytochrome c (CYC) are two mitochondrial apoptogenic factors. In the present study, the cDNA sequences of AIF (LvAIF) and CYC (LvCYC) were cloned from Pacific white shrimp, Litopenaeus vannamei. The LvAIF was 1664 bp, including a 5'-terminal untranslated region (UTR) of 154 bp, an open reading frame (ORF) of 1323 bp encoding a polypeptide of 440 amino acids (aa) and a 3' UTR of 187 bp. The LvCYC was 582 bp, including a 50 bp 5' UTR, a 315 bp ORF encoding for 104 aa, and a 217 bp 3' UTR. The deduced protein of LvAIF contained a conserved Pyr_redox and AIF_C domain at the N-terminal and the predicted LvCYC included a conservative cytochrome_C domain, respectively. Phylogenetic analysis revealed that LvAIF belonged to AIF1 subfamily and showed a close relationship with AIF1 from vertebrates and LvCYC showed the closest relationship with its counterparts from shrimp Marsupenaeus japonicus. Tissue expression profiles showed that both LvAIF and LvCYC existed in most tissues, with the most predominant expression of LvAIF in intestine, then followed muscle and the weakest expression in gill. The highest expression of LvCYC was detected in muscle, and the weakest expression was in hemocytes. Additionally, after white spot syndrome virus (WSSV) infection, the significant up-regulation of LvAIF, LvCYC and caspase 3 transcripts and the increase of pro-caspase 3 and active-caspase 3 protein were detected at most time points (P < 0.05). However, all of the three genes down-regulated in hemocytes in the early stage after WSSV infection. WSSV proliferation and shrimp mortality showed a time-dependent manner and the production of ROS in hemocytes were significantly increased at 6 and 24 h after infection. Our results showed that the apoptotic genes AIF, CYC and caspase 3 might play crucial roles in hepatopancreas, however, the production of ROS in hemocytes might be important in shrimp defense against WSSV infection.

Elevated water temperature increases the levels of reo-like virus and selected innate immunity genes in hemocytes and hepatopancreas of adult female blue crab, Callinectes sapidus

Seasonal changes in water temperature directly affect the aquatic ecosystem. The blue crab, Callinectes sapidus, inhabiting the Chesapeake Bay has been adapted to seasonal changes of the environmental conditions. In this, the animals halt their physiological process of the growth and reproduction during colder months while they resume these processes as water temperatures increase. We aimed to understand the effect of the elevated temperatures on a disease progression of reo-like virus (CsRLV) and innate immunity of adult female C. sapidus. Following a rise in water temperature from 10 to 23 °C, CsRLV levels in infected crabs rose significantly in hemocytes and multiple organs. However, in hemocytes, the elevated temperature had no effect on the levels of three innate immune genes: Cas-ecCuZnSOD-2, CasPPO and CasLpR three carbohydrate metabolic genes: CasTPS, CasGlyP; and CasTreh and the total hemocyte counts (THC). Interestingly, the hemocytes of CsRLV infected animals exposed to 23 °C for 10 days had significantly elevated levels of Cas-ecCuZnSOD-2 and CasTPS, compared to those of the uninfected ones also exposed to the same condition and compared to hatchery-raised females kept at 23 °C. Despite the lack of changes in THC, the types of hemocytes from the animals with high CsRLV levels differed from those of uninfected ones and from hatchery animals kept at 23 °C: CsRLV-infected crabs had hemocytes of smaller size with less cytosolic complexity than uninfected crabs. It therefore appears that the change in temperature influences rapid replication of CsRLV in all internal tissues examined. This implies that CsRLV may have broad tissue tropism. Interestingly, the digestive tract (mid- and hindgut) contains significantly higher levels of CsRLV than hemocytes while hepatopancreas and ovary have lower levels than hemocytes. Innate immune responses differ by tissue: midgut and hepatopancreas with upregulated Cas-ecCuZnSOD-2 similar to that found in hemocytes. By contrast, hepatopancreas showed a down-regulated CasTPS, suggesting carbohydrate stress during infection.

The responsive expression of a chitinase gene in the ridgetail white prawn Exopalaemon carinicauda against Vibrio anguillarum and WSSV challenge

Chitinases are essential enzymes for crustaceans and participates in several biological processes, such as nutrient digestion, morphogenesis, pathogenesis, and pathogen defense. In the present study, the full-length cDNA of Chi (named EcChi) was cloned from the hemocytes of ridgetail white prawn Exopalaemon carinicauda by rapid amplification of cDNA ends methods. The full-length cDNA of EcChi was 1,319 bp, including contains a 5'-untranslated region (UTR) of 42 bp, 3'-UTR of 101 bp with a poly (A) tail, an open-reading frame of 1,176 bp, encoding a 391-amino acid polypeptide with the predicted molecular weight of 43.71 kDa and estimated isoelectric point of 4.78. Sequence analysis revealed that the conserved chitinases family 18 active site was predicted in the amino acid sequence of EcChi. BLAST analysis revealed that amino acids of EcChi shared high identity (61-77 %) with that of other crustaceans. Quantitative real-time PCR analysis indicated that EcChi could be detected in all the tested tissues, and strongly expressed in hepatopancreas of E. carinicauda. After challenged with Vibrio anguillarum and WSSV, EcChi transcripts both in hemocytes and hepatopancreas increased significantly in the first 3 h, respectively. These results indicated that EcChi might be involved in the innate immune responses to V. anguillarum and WSSV in E. carinicauda.

The protein expression profile in hepatopancreas of scallop Chlamys farreri under heat stress and Vibrio anguillarum challenge

Heat stress and pathogen infection have been considered as the main causes for mass mortality of cultured scallops during summer. In the present study, the expression profiles of proteins in the hepatopancreas of scallop Chlamys farreri were examined to reveal the possible mechanisms of physiological responses of scallop beneath heat stress and bacterial infection. An earlier occurred and higher mortality was observed in the scallops from combination treated group (28 °C and an injection of Vibrio anguillarum) in comparison to those in heat stress (28 °C) and bacteria challenge (V. anguillarum injection only) group, as well as control (PBS) and blank (untreated) group. The proteins in the hepatopancreas from scallops post 6 h of treatment were analyzed by using 2-D PAGE and ImageMaster 2D Platinum. There were total 1003 spots detected in control group, 1193 spots in heat stress group, 1263 spots in bacteria challenge group, and 1241 spots in the combination group. Fifteen protein spots expressed differentially between the combination treatment group and the bacteria challenge group were successfully identified by mass spectrometry and they were mainly classified as binding and catalytic proteins, such as endoglucanase, methylmalonate-semialdehyde dehydrogenase, xylose isomerase, tryptophanyl-tRNA synthetase, 40s ribosomal protein SA, glutathione S-transferase 4, and Mitochondrial transcription factor A, etc. These results indicated that the mortality of scallops suffered from the combination treatment was probably attributed to the impaired modulation of digestion and metabolism and ruined protein synthesis caused by heat stress together with bacteria infection. These data also provided valuable insights into the possible mechanisms of summer mortality occurrence of scallop at protein level.

Identification, cloning and characterization of an extracellular signal-regulated kinase (ERK) from Chinese shrimp, Fenneropenaeus chinensis

Extracellular signal-regulated kinase (ERK) is a serine/threonine-specific protein kinase, which participates in signaling transduction pathways that control intracellular events, including resumption of meiosis, embryogenesis, cell differentiation, cell proliferation, cell death and response to radiation. Some virus species evolved the ability to hijack the host cell ERK signaling transduction pathway for viral replications and gene expressions. To obtain a better understanding of ERK, we cloned a cDNA encoding ERK from the muscle of Fenneropenaeus chinensis (FcERK). The FcERK contained a 1098 bp open reading frame (ORF) encoding a protein of 365 amino acid residues with a conserved phosphorylation motif TEY in the kinase activation loop. Pair-wise and multiple sequence alignment revealed that ERK is highly conserved across taxa. The FcERK gene expressions in the hepatopancreas and gill were noticeably higher than the expression observed in the muscle. A challenge test was performed to reveal the responses of FcERK in different tissues to white spot syndrome virus (WSSV) infection. Post WSSV challenge, the FcERK expression in the gill significantly increased during the early stage of the viral infection, the FcERK expression in the muscle increased later than that in the gill, and the FcERK expression in the hepatopancreas significantly decreased. The FcERK gene expression profile accorded with the results that the virus primarily infects tissues originating from the ectoderm, with less infection of the tissues originating from the mesoderm, and hardly any infection in the tissues originating from the entoderm. Two single nucleotide polymorphisms (SNPs) were identified in the FcERK gene, involving C/T transition. The SNP genotypes of two groups of shrimps, respectively comprising 96 WSSV-resistant shrimps and 96 WSSV-susceptible shrimps were obtained using a high-resolution melting (HRM) method. In the two groups, the MAFs of both sites were greater than 0.05, and no site departed significantly (P < 0.05) from HWE. The genotype distributions of both mutation sites between the two groups were not significantly different. These results lead to a better understanding of the molecular mechanisms of the host-virus interaction and provide useful information for disease control.

Metagenomic identification of a nodavirus and a circular ssDNA virus in semi-purified viral nucleic acids from the hepatopancreas of healthy Farfantepenaeus duorarum shrimp

Fisheries and aquaculture are impacted sporadically by newly emerged viral diseases. In most cases, searches for a causative pathogen only occur after a serious disease has emerged. As random shotgun sequencing (metagenomics) offers opportunities to identify novel viruses preemptively, the method was tested on nucleic acids extracted from the hepatopancreas of 12 healthy northern pink shrimp Farfantepenaeus duorarum captured from the Gulf of Mexico. Among the sequences, a nodavirus (Farfantepenaeus duorarum nodavirus, FdNV) and a virus with similarities to circoviruses and cycloviruses that possess circular single-stranded DNA (ssDNA) genomes, were identified. The FdNV genome sequence was most closely related phylogenetically to nodaviruses causing white tail disease in Macrobrachium rosenbergii and muscle necrosis disease in Litopenaeus vannamei. While the circular ssDNA virus represents the third to be detected in association with a marine invertebrate, transmission trials are needed to confirm its infectivity for F. duorarum. This study highlights the potential for using metagenomic approaches in fisheries and aquaculture industries to identify new potential pathogens in asymptomatic marine invertebrates, uncharacterized pathogens causing a new disease, or multiple pathogens associated with disease syndromes.

Identification and expression profiles of grass carp Ctenopharyngodon idella tlr7 in responses to double-stranded RNA and virus infection

The toll-like receptor 7 (tlr7) gene was identified and characterized from grass carp Ctenopharyngodon idella (designated as citlr7), and the messenger (m)RNA expression profiles were examined in vivo and in vitro. The citlr7 genomic sequence consists of 4276 nucleotides (nts), including two exons and one intron. The full length of citlr7 complementary (c)DNA sequence is 3354 nts with the longest open reading frame (ORF) of 3156 nts encoding a peptide of 1051 amino acids. citlr7 mRNA expression was high in spleen, skin and heart, and low in hepatopancreas, muscle, head kidney and trunk kidney in healthy fish. The expression of citlr7 was rapidly and significantly up-regulated at 6 h after grass carp reovirus (GCRV) injection (72·91 fold, P < 0·05), and recovered to the original level at 24 h post-injection in the spleen. The citlr7 transcript was rapidly and significantly down-regulated at the 6 h time point (0·32 fold, P < 0·05) and retrieved the normal level at 72 h post-injection in the hepatopancreas. The citlr7 transcripts were rapidly and significantly inhibited at 2 h post-GCRV infection in the C. idella kidney (CIK) cell line (0·62 fold, P < 0·05), and were rapidly and significantly elevated by the stimulation of the synthetic double-stranded RNA polyriboinosinic-polyribocytidylic acid sodium salt [poly(I:C)] in CIK in a dose and time-dependent manner (P < 0·05). The results imply that citlr7 is involved in the responses to double-stranded RNA and virus infection.

Two types of calmodulin play different roles in Pacific white shrimp (Litopenaeus vannamei) defenses against Vibrio parahaemolyticus and WSSV infection

Calmodulin (CaM) plays an important role in calcium-dependent signal transduction pathways. In the present study, two alternative splicing isoforms of CaM (named LvCaM-A and LvCaM-B) cDNA were cloned from the Pacific white shrimp, Litopenaeus vannamei. LvCaM-A was of 1101 bp, including a 5'-terminal untranslated region (UTR) of 70 bp, a 3'-terminal UTR of 581 bp and an open reading frame (ORF) of 450 bp encoding a polypeptide of 149 amino acids with a calculated molecular weight (Mw) of 17 kDa and pI of 4.41. LvCaM-B was 689 bp, including a same 5'-UTR of 70 bp, a 3'-terminal UTR of 109 bp and an ORF of 510 bp encoding a polypeptide of 169 amino acids with a calculated Mw of 19 kDa and pI of 4.36. Both LvCaM-A and LvCaM-B contained 4 conservative EF-hand motifs. Quantitative real-time reverse transcription PCR analysis revealed LvCaM-A to be expressed in most shrimp tissues, with the predominant expression in nerve and the weakest expression in heart. However, LvCaM-B expression level was much weaker than those of LvCaM-A in all the tested tissues with main expression in hepatopancreas. The expression of LvCaM-A and LvCaM-B after challenge with Vibrio parahaemolyticus and WSSV were tested in hemocytes, hepatopancreas and nerve. The results indicated that LvCaM-A and LvCaM-B transcripts could be significantly induced in hemocytes and hepatopancreas respectively by injection with V. parahaemolyticus. The highest expression of LvCaM-A was in the hemocytes with 2.3 times (at 48 h) greater expression than in the control (p < 0.05). However, sharp down-regulation of both LvCaM-A and LvCaM-B were detected in nerve after Vibrio- and WSSV injection (p < 0.05). These results suggested that CaM might play an important role in shrimp's defense against pathogenic infection.

The transcriptomic response to viral infection of two strains of shrimp (Litopenaeus vannamei)

The extent to which data-intensive studies of the transcriptome can provide insight into biological responses is not well defined, especially in the case of species (such as shrimp) where much physiological and biochemical knowledge is missing. In this study we took a transcriptomic approach to gain insight into the response to viral infection of two strains of the Pacific whiteleg shrimp (Litopenaeus vannamei) that differ in their resistance to Taura Syndrome Virus (TSV). Changes in gene expression in the hepatopancreas following infection with TSV and Yellow Head Virus (YHV) were assessed using a cDNA microarray containing 2469 putative unigenes. The null hypothesis tested was that significant differences between the transcriptomic responses to viral infection of resistant and sensitive strains would not be detected. This hypothesis was broadly rejected, with the most surprising observation being that the baseline (control, unchallenged) sensitive and resistant strains expressed distinguishable transcriptomic signatures. The resistant line was pre-disposed to lower expression of genes encoding viral (and host) proteins. Many of the genes differentiating resistant and sensitive lines are involved in protein metabolism, cellular trafficking, immune defense and stress response, although it was not possible to clearly identify candidate genes responsible for TSV resistance. In contrast to TSV challenge, YSV either failed to perturb the host transcriptome or created a "confused" response that was difficult to interpret.

Duplex real-time PCR for detection and quantification of monodon baculovirus (MBV) and hepatopancreatic parvovirus (HPV) in Penaeus monodon

We describe a duplex real-time PCR assay using TaqMan probes for the simultaneous detection of monodon baculovirus (MBV) and hepatopancreatic parvovirus (HPV). Both MBV and HPV are shrimp enteric viruses that infect intestinal and hepatopancreatic epithelial cells. Both viruses can cause significant mortalities and depressed growth in infected larval, postlarval, and early juvenile stages of shrimp, and thus present a risk to commercial aquaculture. In this duplex assay, we combined 2 single real-time PCRs, amplifying MBV and HPV, in a one-tube PCR reaction. The 2 viruses were distinguished by specific fluorescent labels at the 5' end of TaqMan probes: the MBV probe was labeled with dichlorodimethoxyfluorescein (JOE), and the HPV probe was labeled with 6-carboxyfluorescein (FAM). The duplex real-time PCR assay was performed in a multi-channel real-time PCR detection system, and MBV and HPV amplification signals were separately detected by the JOE and FAM channels. This duplex assay was validated to be specific to the target viruses and found to have a detection limit of single copies for each virus. The dynamic range was found to be from 1 to 1 x 10(8) copies per reaction. This assay was further applied to quantify MBV and HPV in samples of infected Penaeus monodon collected from Malaysia, Indonesia, and Thailand. The specificity and sensitivity of this duplex real-time PCR assay offer a valuable tool for routine diagnosis and quantification of MBV and HPV from both wild and farmed shrimp stocks.

Comparative proteomic profiles of the hepatopancreas in Fenneropenaeus chinensis response to white spot syndrome virus

White spot syndrome virus (WSSV) infects all shrimp species and is the greatest detriment to shrimp culture. To better understand the mechanism of molecular responses to WSSV infection in Chinese white shrimp Fenneropenaeus chinensis, two dimensional electrophoresis (2-DE) was used. Differentially expressed proteins in the hepatopancreas of control and WSSV-injected Chinese white shrimp between (6, 12 and 24 h post-injection) were screened. Quantitative intensity analysis and mass spectrometry revealed that 54 spots of 47 proteins were significantly up-regulated, including some immune-related proteins, such as Toll receptor precursor, Leu-rich repeat protein, peroxinectin and serine proteinase-like protein. Fourteen spots of 13 proteins, such as heat shock protein, ATP synthase sub-unit beta and thrombospondin, were down-regulated in WSSV-infected shrimps. Protein expression patterns of the infected shrimp were drastically altered by WSSV infection. Some of the altered proteins were further investigated at the mRNA level using semi-quantitative reverse transcript PCR. These data may provide some information about shrimp proteins that participate in the WSSV infection process.

A thioredoxin response to the WSSV challenge on the Chinese white shrimp, Fenneropenaeus chinensis

Thioredoxin (TRX) is involved in cell redox homeostasis. In addition, it is responsible for maintaining proteins in their reduced state. In our study, a Fenneropenaeus chinensis thioredoxin (FcTRX) gene was identified from the Chinese white shrimp. The full length of FcTRX was 777 bp, including a 60 bp 5' untranslated region (UTR), a 318 bp open reading frame (ORF) encoding a 105 amino acids protein, and a 399 bp 3' UTR. FcTRX contained a TRX domain with a conserved motif of Cys-Gly-Pro-Cys (CGPC). No signal peptide was predicted by SMART analysis. The molecular mass and pI of FcTRX were 12 kDa and 4.62, respectively. FcTRX is a widely distributed gene, and its mRNA is detected in hemocytes, hearts, hepatopancreas, gills, stomach, and intestine from an unchallenged shrimp. The expression level of FcTRX was the highest in hepatopancreas, where it was down-regulated to the lowest level at 12 h white spot syndrome virus (WSSV) challenge. In the gills, it went up to the highest level at 6 h. Western blot showed that FcTRX protein in hepatopancreas challenged with WSSV was down-regulated from 2 h to 12 h and then restored to the level similar to that of unchallenged shrimp at 24 h. In the gills challenged with WSSV, the FcTRX protein was up-regulated from 6 h to 24 h. Our research indicated its possible role in the anti-WSSV innate immunity of shrimps.

Parvo-like virus in the hepatopancreas of freshwater prawns Macrobrachium rosenbergii cultivated in Thailand

A survey of cultivated giant freshwater prawns Macrobrachium rosenbergii from Thailand revealed the presence of unusual spherical to ovoid inclusions in nuclei of hepatopancreas tubule epithelial cells. These began as small eosinophilic inclusions that became more basophilic as they increased in size. They were present in both R-cells and E-cells but were largest and deeply basophilic only in the E-cells. Confocal laser microscopy revealed that stained nucleic acid fluorescence from the inclusions was lost by treatment with DNase I specific for double- and single-stranded DNA and also lost or reduced by treatment with mungbean nuclease specific for single-stranded nucleic acids. Transmission electron microscopy (TEM) revealed that the inclusions contained tightly packed, unenveloped, viral-like particles of approximately 25 to 30 nm diameter, resembling those produced by shrimp parvoviruses. However, PCR, in situ hybridization and immunohistochemical tests for shrimp parvoviruses previously reported from Thailand were all negative. These results suggested that the inclusions contained a parvo-like virus, not previously reported from M. rosenbergii in Thailand.

Molecular isolation and characterization of a novel occlusion body protein gene from Penaeus monodon nucleopolyhedrovirus

The full-length of the occlusion body (OB) protein gene of Penaeus monodon nucleopolyhedrovirus (PemoNPV) was successfully isolated. The OB gene sequence contained an open reading frame (ORF) of 1359 nucleotides encoding a protein of 452 amino acid residues with a predicted molecular mass of 50.6 kDa. A putative late promoter element, TAAG, was identified 72 nt upstream of the translation start site. The amino acid sequences of tryptic digested peptides of PemoNPV OB protein obtained from LC-MS analysis matched quite well with various regions of deduced amino acid sequences. Recombinant PemoNPV OB proteins specifically reacted with monoclonal antibodies to PemoNPV OB protein. After comparison with nucleotide database, the PemoNPV OB ORF demonstrated 67% identity to an uncharacterized ORF of a baculovirus pathogenic for Penaeus vannamei. However, comparison against protein databases revealed no significant homology to other known proteins. To our knowledge, this PemoNPV OB gene is the first isolated and characterized gene of nucleopolyhedrovirus from shrimp.

Nucleotide sequence of a Madagascar hepatopancreatic parvovirus (HPV) and comparison of genetic variation among geographic isolates

A segment of Madagascar hepatopancreatic parvovirus (HPV) genomic sequence (5742 nucleotides) was determined through PCR and direct sequencing. This nucleotide sequence was compared to isolates from Australia, Thailand, Korea, and Tanzania, and the mean distance was determined to be 17%. The Madagascar HPV is closest to the Tanzania isolate (12%), followed by isolates from Korea (15%), Australia (17%) and Thailand (20%). Analysis of the genomic structure revealed that this HPV sequence is comprised of one partial Left open reading frame (ORF) (349 amino acids, aa) and complete Mid (578 aa) and Right (820 aa) ORFs. The amino acid sequences of the 3 ORFs were compared among isolates. The Right ORF was found to have the highest variation with a mean distance of 24%. This was followed by the Left and Mid ORF with distances of 13 and 7%, respectively. A phylogenetic analysis based on the amino acid sequence of the Right ORF divides 7 HPV isolates into 3 well-separated groups: Korea, Thailand, and Australia. The Madagascar HPV clustered with the Korea and Tanzania isolates. In Madagascar, HPV has been detected by histological examination since the 1990s. PCR analysis of a recent (2007) sampling showed a 100% prevalence. HPV was also detected in Mozambique with a 100% prevalence. High (95%) prevalence of HPV was found in wild Penaeus merguinesis collected from New Caledonia. These results indicate that HPV displays a high degree of genetic diversity and is distributed worldwide among populations of penaeid shrimp.

Cancer pagurus bacilliform virus (CpBV) infecting juvenile European edible crabs C. pagurus from UK waters

This study provides the first description of an intranuclear bacilliform virus infecting the hepatopancreatic epithelial cells of juvenile European edible crab Cancer pagurus from the English Channel, UK. This is the first field report of a virus infecting a member of the Cancer genus and follows a report of a different virus infection detected in C. pagurus held under experimental conditions. We have named the virus Cancer pagurus bacilliform virus (CpBV). The morphology and size of the nucleocapsid and the complete virion align the virus most closely with intranuclear bacilliform viruses reported from other decapod species. The virus was only observed in juvenile C. pagurus with carapace widths ranging between 20 and 70 mm. Viral infection was not observed in crabs above the minimum landing size of 140 mm carapace width. Due to the importance of C. pagurus as a fisheries target, the increasing relative reliance on crustacean fisheries in Europe and the relative dearth of information on diseases of this species, it is pertinent to consider the effects that infections such as CpBV may have on mortality of juvenile crabs and on the sustainability of the fishery as a whole.

Presence of Panulirus argus virus 1 (PaV1) in juvenile spiny lobsters Panulirus argus from the Caribbean coast of Mexico

Macroscopic evidence, histological sections, transmission electron microscopy (TEM) evaluation, and PCR analyses of 25 apparently diseased juvenile spiny lobsters Panulirus argus from the reef lagoon of Puerto Morelos, Mexico, showed the presence of Panulirus argus Virus 1 (PaV1). Cowdry Type A intranuclear viral inclusions were observed in histological analyses, icosahedral viral particles were observed by TEM, and PCR using specific primers for PaV1 amplified a fragment of 499 bp. This is the first report of PaV1 infecting P. argus outside the Florida Keys, USA.

A reovirus disease in cultured mud crab, Scylla serrata, in southern China

A reovirus, designated mud crab reovirus (MCRV), associated with large economic losses was recently isolated from marine cultured mud crab, Scylla serrata, in southern China. The complete viral particle is 70 nm in diameter, icosahedral and non-enveloped. The virus infects connective tissue cells of the hepatopancreas, gills and intestine in mud crab and develops in the cytoplasm. Hundred per cent mortality was observed in mud crab experimentally infected by intramuscular injection, bath inoculation and oral inoculation, while cohabitation infection caused 80% mortality. The viral genome consists of 13 linear dsRNA segments, with an electrophoretic pattern 1/5/7. The results of this study suggest that the virus is highly pathogenic and can be transmitted enterically as well as via the body surface of mud crab. Although the genomic organization of this virus is different from that of the other crab reoviruses, CcRV-W2 and DpPV, all three of these reoviruses have similar electrophoresis patterns. Therefore, MCRV may be a new member of the DpPV and CcRV-W2 group.

TaqMan real-time PCR for detection of hepatopancreatic parvovirus from Australia

Hepatopancreatic parvovirus is an emerging disease in crustacean aquaculture. Consequently, methods of detection are needed that enable the sensitive detection and confirmation of the virus better than currently used methods such as histology and conventional polymerase chain reaction (PCR). A TaqMan based real-time PCR assay was developed for the detection of the Australian isolate of hepatopancreatic parvovirus which is only 85% similar to its nearest known relative. The TaqMan assay was developed within the capsid protein region of the genome and is optimised to detect as little as 10 copies of the targeted sequence per PCR vial. The hepatopancreatic parvovirus primers and probe were HPV140F 5'-CTA CTC CAA TGG AAA CTT CTG AGC-3', HPV140R 5'-GTG GCG TTG GAA GGC ACT TC-3' and HPV140probe 5'-FAM TAC CGC CGC ACC GCA GCA GC TAMRA-3', respectively. The assay was specific for the hepatopancreatic parvovirus strain from Australian Penaeus merguiensis as it did not detect related crustacean and canine parvoviruses from Australia. In addition, the very low homology of the target sequence with published sequences from the Thai and Korean strains of hepatopancreatic parvovirus and other prawn viruses such as WSSV, suggested this assay would be specific for the Australian hepatopancreatic parvovirus isolate. Furthermore, it detected hepatopancreatic parvovirus in 22/22 wild-caught P. merguiensis clinical samples and 473/545 (87%) farmed P. merguiensis. This assay has the potential to be used for diagnostic purposes and in robotic applications, particularly for the detection and quantitation of low-grade infections.

Detection of Panulirus argus Virus 1 (PaVI) in the Caribbean spiny lobster using fluorescence in situ hybridization (FISH)

Panulirus argus Virus 1 (PaV1) is the first virus known to be pathogenic to a wild lobster. It infects the Caribbean spiny lobster P. argus from the Florida Keys, and has a predilection for juveniles. The monitoring of the virus in wild populations and study of its behavior in the laboratory require the development of reliable diagnostic tools. A sensitive and specific fluorescence in situ hybridization (FISH) assay was developed for detection of PaV1. The lower detection limit using a 110 bp DNA probe in a dot-blot hygridization for PaV1 DNA was 10 pg of cloned template PaV1 DNA and 10 ng of genomic DNA extracted from the hemolymph of diseased spiny lobster. The fluorescein (FITC)-labeled probe specifically hybridized to PaVl-infected cells in the hepatopancreas, hindgut, gills, heart, foregut, and nerve tissues. FITC staining was observed around the inner periphery of the nuclear membrane, with lighter staining in a more dispersed pattern within the nucleus. The probe did not hybridize with host tissues of uninfected spiny lobsters, nor did it cross-react with 4 other virus samples tested. This assay will facilitate our understanding of the pathogenesis of the viral disease and help in monitoring efforts directed at determining the prevalence of PaV1 in juvenile nurseries for this lobster.

Cloning, expression and identification of ferritin from Chinese shrimp, Fenneropenaeus chinensis

Ferritin, the iron storage protein, plays a key role in iron metabolism. A cDNA encoding ferritin (FcFer) was cloned from hepatopancreas of Chinese shrimp, Fenneropenaeus chinensis. The predicted protein contains 170 amino acid residues with a predicted molecular weight (MW) about 19, 422.89 Da and theoretical isoelectric point (PI) of 4.73. Amino acid alignment of FcFer revealed 97% homology with Litopenaeus vannamei ferritin. Results of the RT-PCR showed that the expression of FcFer mRNA was up-regulated after shrimp was challenged with either white spot syndrome virus (WSSV) or heavy metal ions (Zn2+ and Cu2+) in the laboratory. A fusion protein containing FcFer was produced and the purified recombinant protein exhibited similar function of iron uptake in vitro. The result of in-gel digestion and identification using LC-ESI-MS showed that two peptide fragments (-DDVALPGFAK- and -LLEDEYLEEQVDSIKK-) of the recombinant protein were identical to the corresponding sequence of L. vannamei ferritin. The recombinant FcFer protein will be proved useful for study on the structure and function of ferritin in F. chinensis.

Generation of monoclonal antibodies specific to Hepatopancreatic parvovirus (HPV) from Penaeus monodon

Hepatopancreatic parvovirus (HPV) was isolated from the hepatopancreas (HP) of slow growth Penaeus monodon by urografin gradient centrifugation. The presence of HPV in the fraction was monitored by PCR and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Only 1 major 54 kDa protein band was observed in the strong PCR-positive fractions used to immunize mice for monoclonal antibody production. After cell fusion, the first step in selecting specific antibodies was performed by dot-blot assay with purified HPV viral particles. The second screening step was carried out using Western blots of purified HPV proteins and immunohistochemistry of HPV-infected HP tissue. Four monoclonal antibodies were isolated; these bound to the 54 kDa protein in Western blots and to intranuclear inclusion bodies in tubule epithelial cells of HPV-infected prawn tissue by immunohistochemistry. None of the antibodies showed cross-reactivity either to uninfected shrimp tissue or to other shrimp viruses tested. These reagents have potential for use in developing a highly sensitive immunoassay such as sandwich ELISA or a convenient kit for detection of HPV infection.

OIE white spot syndrome virus PCR gives false-positive results in Cherax quadricarinatus

White spot syndrome virus (WSSV) is an intranuclear bacilliform virus (IBV) that is a serious, notifiable crustacean pathogen. The Office International des Epizooties (OIE) PCR protocol for WSSV uses primer sets initially developed by Lo et al. (1996). It yields a first-step PCR amplicon of 1441 bp and a nested PCR amplicon of 941 bp. An amplicon (941 bp) purported to specifically detect WSSV was obtained when using template DNA extracted from Cherax quadricarinatus in a WSSV PCR detection protocol recommended by the OIE. Sequencing and analysis of the 941 bp amplicon and an occasional 550 bp amplicon from C. quadricarinatus revealed no phylogenetic relationship with WSSV, and suggested a possible lack of sufficient primer specificity for WSSV in the OIE test. This suggestion was supported by the fact that the OIE outer primer sequence (146F1) was present in both the forward and reverse position of the 941 bp and the forward position of the 550 bp nested amplicons from C. quadricarinatus. As WSSV is a notifiable pathogen, the consequences of false-positive results are harsh in WSSV-free zones and can lead to incorrect quarantine and unnecessary destruction of animals. Therefore, urgent attention and revision is necessary for the current OIE PCR protocol for WSSV detection.

Methods to enhance the intensity of intranuclear bacilliform virus infection in Cherax quadricarinatus

Many studies have examined the morphology, pathology and epizootiology of the intranuclear bacilliform virus (IBV) of Cherax quadricarinatus, but little research has been conducted to acquire specific knowledge of the virus. This is partly due to difficulties in detecting the virus and in obtaining sufficient material for viral isolation and purification. As quantified by light microscopy, we significantly (p < 0.01) enhanced IBV intensities from 10.56 to 16.67% in C. quadricarinatus by using salinity stress (12 ppt) and ingestion of infected hepatopancreatic tissue, which increased intensities from 4.33 to 10.77%. It was also found that phosphotungstic acid-eosin stain was superior to standard haematoxylin and eosin stain in visualizing IBV inclusion bodies. It is expected that these new techniques will enhance the detectability of the virus and provide sufficient viral material for viral purification, characterization and development of molecular tools for detection and phylogenetic analysis.

Pathology and ultrastructure of an intranuclear bacilliform virus (IBV) infecting brown shrimp Crangon crangon (Decapoda: Crangonidae)

The brown shrimp Crangon crangon supports an important fishery in Europe (over 25000 t, valued at 80 million euros in 2000). Through the course of histopathological screening of crustaceans from the Clyde estuary, western Scotland, for the biological effect of contaminants, we have discovered a highly prevalent (up to 100%) non-occluded intranuclear bacilliform virus (IBV) infection in the hepatopancreatic tubule epithelia and midgut epithelia of wild C. crangon. This is the first report of an IBV in this family. We have termed this virus Crangon crangon bacilliform virus (CcBV). Histological and ultrastructural observations suggest that this virus is similar to other IBVs previously described from crabs and penaeid shrimps. The nuclei of virus-infected epithelial cells contained an eosinophilic, hypertrophied viroplasm that marginalised the chromatin of the host nucleus. Infected cells were often separated from their neighbouring cells and their nuclei appeared apoptotic. In heavily infected shrimp, apoptotic cells were expelled into the lumen of the hepatopancreatic tubule or the midgut. Following this stage, some hepatopancreatic tubules became degenerate, with remnants of the basement membrane and myoepithelial lining remaining. Transmission electron microscopy of hypertrophic nuclei revealed the presence of rod-shaped and cylindrical, envelope-bound virions. These virions did not form arrays and were not embedded within occlusion bodies, but did appear to be partially occluded in an amorphous matrix that corresponded to a granular viroplasm. The ultrastructure, morphology and size of the nucleocapsid and the complete virion aligns the virus most closely to the IBVs previously reported from other decapod crustaceans. Due to the pathological manifestation of IBV infection in C. crangon, it appears likely that it can act as a population modulator, particularly at sites where infection prevalence is high, such as that observed in the Clyde estuary.

Occurrence, histopathology and experimental transmission of hepatopancreatic parvovirus infection in Penaeus monodon postlarvae

Hepatopancreatic parvovirus (HPV) was detected in samples of Penaeus monodon post-larvae (PL-13, PL-18, PL-19, PL-26) from 2 hatcheries in 2 provinces (Samar and Iloilo) in the Philippines. The percentage of infection was 20 to 100% in postlarvae obtained from the hatchery in Samar in August 2001. Postlarvae from the hatchery in Iloilo, sampled in October and November 2001, had 70 to 99% HPV infection. Wet mounts of squashed hepatopancreatic tissue stained with malachite green (wet-mount technique) and histopathology revealed the presence of large, usually single, basophilic intranuclear inclusion bodies in the distal tubules, which led to displacement of the nucleoli. Light microscopy showed ovoid to spherical inclusion bodies, 5 to 11 mmicrom in diameter. Transmission electron microscopy revealed that the inclusion bodies were composed of electron-dense granular material and virions. The virions appeared roughly spherical and averaged 18 to 22 nm in diameter. An experiment was undertaken to induce HPV infection by feeding P. monodon postlarvae with virus-infected postlarvae. P. monodon postlarvae (PL-16), initially determined as free from HPV, were found HPV-positive 24 h after being fed with infected material. The percentage of infection ranged from 30% at Day 1 post-infection (p.i.) to 100% at Day 7 p.i. determined by the wet-mount technique and by histopathology. This is the first report of a successful horizontal transmission of HPV in P. monodon postlarvae.

Detection by PCR of hepatopancreatic parvovirus (HPV) and other viruses in hatchery-reared Penaeus monodon postlarvae

The prevalence of hepatopancreatic parvovirus (HPV), monodon baculovirus (MBV) and white spot syndrome virus (WSSV) in samples of Penaeus monodon postlarvae (PL10 to PL20, 10 to 20 d old postlarvae) in India was studied by PCR. Samples collected from different hatcheries, and also samples submitted by farmers from different coastal states, were analyzed. HPV was detected in 34%) of the hatchery samples and 31% of the samples submitted by farmers, using a primer set designed for detection of HPV from P. monodon in Thailand. However, none of these samples were positive using primers designed for detection of HPV from P. chinensis in Korea. This indicated that HPV from India was more closely related to HPV from P. monodon in Thailand. MBV was detected in 64% of the samples submitted by the farmers and 71% of the hatchery samples. A total of 84 % of the samples submitted by farmers, and 91% of the hatchery samples, were found positive for WSSV. Prevalence of concurrent infections by HPV, MBV and WSSV was 27% in hatchery samples and 29%, in samples submitted by farmers. Only 8% of the hatchery samples and 16% of the samples submitted by farmers were negative for all 3 viruses. This is the first report on the prevalence of HPV in P. monodon postlarvae from India.