Biomedical subjects

Donald V Lightner

Publications and source records attributed to Donald V Lightner.

At least 19 recordsLinked to original sources

PubMed2006

Viral interference between infectious hypodermal and hematopoietic necrosis virus and white spot syndrome virus in Litopenaeus vannamei.

White spot syndrome virus (WSSV) is highly virulent and has caused significant production losses to the shrimp culture industry over the last decade. Infectious hypodermal and hematopoietic necrosis virus (IHHNV) also infects penaeid shrimp and, while being less important than WSSV, remains a major cause of significant production losses in Litopenaeus vannamei (also called Penaeus vannamei) and L. stylirostris (also called Penaeus stylirostris). These 2 viruses and their interactions were previously investigated in L. stylirostris. We report here laboratory challenge studies carried out to determine if viral interference between IHHNV and WSSV also occurs in L. vannamei, and it was found that experimental infection with IHHNV induced a significant delay in mortality following WSSV challenge. L. vannamei infected per os with IHHNV were challenged with WSSV at 0, 10, 20, 30, 40 and 50 d post-infection. Groups of naïve shrimp infected with WSSV alone died in 3 d whereas shrimp pre-infected with IHHNV for 30, 40 or 50 d died in 5 d. Real-time PCR analysis showed that the delay correlated to the IHHNV load and that WSSV challenge induced a decrease in IHHNV load, indicating some form of competition between the 2 viruses.

Animals↗

PubMed2006

Comparison of four Taura syndrome virus (TSV) isolates in oral challenge studies with Litopenaeus vannamei unselected or selected for resistance to TSV.

Taura syndrome virus (TSV) infection in TSV-resistant (TSR) and TSV-susceptible (Kona) Litopenaeus vannamei (also called Penaeus vannamei) was investigated using histology, in situ hybridization (ISH), conventional reverse transcription polymerase chain reaction (RT-PCR) assays, and SYBR-Green real-time RT-PCR analysis. The shrimp were challenged by feeding with minced tissues of L. vannamei infected with 4 genotypic variants of TSV (Bz01, Th04, UsHi94, and Ve05). Survival probabilities of TSR shrimp were higher than those for Kona shrimp with all 4 variants. Th04, UsHi94, and Ve05 gave no Taura syndrome lesions with TSR shrimp. In contrast, TSR shrimp challenged with Bz01 and Kona shrimp with all 4 TSV variants exhibited severe necrosis of cuticular epithelial cells and lymphoid organ spheroids, indicative of acute and chronic phases of TSV infection, respectively. TSV was not detected by RT-PCR in TSR shrimp infected with Th04, UsHi94, and Ve05, or in Kona shrimp infected with Ve05 but was detected in TSR shrimp infected with Bz01 and in Kona shrimp infected with Bz01, Th04, and UsHi94. Real-time RT-PCR revealed that mean TSV copy numbers in TSR shrimp infected with Bz01, Th04, and UsHi94 were significantly (p < 0.0005) lower than those in Kona shrimp. In contrast, mean TSV copy numbers in TSR and Kona shrimp infected with Ve05 were not significantly different (p > 0.4). The results show that TSR L. vannamei are susceptible to infection but give high survival rates following challenge by all 4 variants of TSV.

Analysis of Variance↗

PubMed2006

Infectious hypodermal and hematopoietic necrosis virus (IHHNV)-related sequences in the genome of the black tiger prawn Penaeus monodon from Africa and Australia.

We found an infectious hypodermal and hematopoietic necrosis virus (IHHNV)-related sequence within the shrimp genome in populations of Penaeus monodon from Africa and Australia. IHHNV is a single-stranded DNA virus that has caused severe mortality and stunted growth in penaeid shrimp. Recently, IHHNV-related sequences were found in samples of P. monodon from Madagascar and Tanzania. These sequences vary considerably (14 and 8%, respectively) from that of IHHNV found in association with viral epidemics. Laboratory bioassays were carried out with P. monodon and Litopenaeus vannamei to determine if either of these IHHNV-related sequences is infectious. We used juvenile and adult P. monodon containing the virus-related sequences from four geographic regions to generate inocula and tissues for feeding. Specific pathogen free P. monodon and L. vannamei were used as indicator shrimp. During the 2-4 week bioassays, none of the indicator shrimp showed signs of infection or disease. Results of both PCR assays and histological examination of the indicator shrimp were negative for IHHNV infection, indicating that the Africa type IHHNV-related sequences are not infectious. With the shrimp containing the Madagascar type IHHNV-related sequence (designated as type A), we performed genome walking at the 3' end of the virus-related sequence and found that this virus-related sequence is part of the P. monodon genome. A fragment of 1.9 kb flanking sequence was cloned and sequenced. Sequence analysis showed that this flanking sequence contains shrimp microsatellite DNA. Also, its translated amino acid sequence was highly similar to a retrotransposon. This result provides molecular evidence that the type A IHHNV-related sequence is shrimp DNA. This sequence was found in the P. monodon collected from Africa and Australia.

Africa↗

PubMed2006

Purification and characterization of infectious myonecrosis virus of penaeid shrimp.

The causative agent of myonecrosis affecting cultured Penaeus vannamei in Brazil was demonstrated to be a virus after purification of the agent from infected shrimp tissues. Purified viral particles were injected into specific pathogen-free P. vannamei, resulting in a disease that displayed the same characteristics as those found in the original shrimp used for purification. The virus was named infectious myonecrosis virus (IMNV). The viral particles were icosahedral in shape and 40 nm in diameter, with a buoyant density of 1.366 g ml(-1) in caesium chloride. The genome consisted of a single, double-stranded (dsRNA) molecule of 7560 bp. Sequencing of the viral genome revealed two non-overlapping open reading frames (ORFs). The 5' ORF (ORF 1, nt 136-4953) encoded a putative RNA-binding protein and a capsid protein. The coding region of the RNA-binding protein was located in the first half of ORF 1 and contained a dsRNA-binding motif in the first 60 aa. The second half of ORF 1 encoded a capsid protein, as determined by amino acid sequencing, with a molecular mass of 106 kDa. The 3' ORF (ORF 2, nt 5241-7451) encoded a putative RNA-dependent RNA polymerase (RdRp) with motifs characteristic of totiviruses. Phylogenetic analysis based on the RdRp clustered IMNV with Giardia lamblia virus, a member of the family Totiviridae. Based on these findings, IMNV may be a unique member of the Totiviridae or may represent a new dsRNA virus family that infects invertebrate hosts.

Amino Acid Sequence↗

PubMed2005

Different responses to infectious hypodermal and hematopoietic necrosis virus (IHHNV) in Penaeus monodon and P. vannamei.

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is widespread in cultured Penaeus monodon and P. vannamei in Thailand. It causes runt-deformity syndrome that is characterized by physical abnormalities and stunted growth in P. vannamei, but causes no apparent disease in P. monodon. In both species, the virus may produce Cowdry Type A inclusions in tissues of ectodermal and mesodermal origin, but these are common in P. vannamei and rare in P. monodon. The virus can be more easily detected in both species by IHHNV-specific PCR primers. By in situ hybridization (ISH) using specific IHHNV probes, fixed phagocytes associated with myocardial cells tended to show strong positive reactions in both shrimp species. Ovarian and neural tissue (neurons in the nerve ganglia and glial cells in the nerve cord) were ISH positive for IHHNV only in P. vannamei. By transmission electron microscopy, necrotic cells were found in the gills of IHHNV-infected P. vannamei, while paracrystalline arrays of virions and apoptotic cells rather than necrotic cells were found in the lymphoid organ of IHHNV-infected P. monodon. Thus, it is possible that apoptosis in P. monodon contributes to the absence of clinical disease from IHHNV. These findings reveal different responses to IHHNV infection by the 2 shrimp species. A curious feature of IHHNV infection in P. monodon was inconsistency in the comparative viral load amongst tissues of different specimens, as detected by both ISH and real-time PCR. This inconsistency in apparent tissue preference and the reasons for different cellular responses between the 2 shrimp species remain unexplained.

Animals↗

PubMed2005

Experimental infection of Penaeus monodon with Taura syndrome virus (TSV).

Clinical signs and lesions of Taura syndrome virus (TSV) infection in Penaeus monodon have not been documented although the virus has been detected in this shrimp species by reverse transcription polymerase chain reaction (RT-PCR). This study provides the first evidence of TSV infection in P. monodon by histological and in situ hybridization (ISH) analyses. We performed experimental bioassays with groups of P. monodon using inocula of P. monodon and Litopenaeus vannamei (Th04PmTSV and Th04LvTSV, respectively), which were collected from Thailand in 2004 and found to be positive for TSV by RT-PCR. Samples of shrimp for histological and ISH analyses were collected on Days 2, 14, and 28 post-inoculation. Mortality among TSV-inoculated P. monodon appeared on Day 3, with 2 out of 10 shrimp dying. Severe necrosis of cuticular epithelial cells and lymphoid organ spheroids, indicative of acute and chronic phase lesions of TSV infection, respectively, were detected in the samples. Sequence analyses of the capsid protein 2 (CP2) gene showed that Th04PmTSV and Th04LvTSV isolates were different; however, both belonged to a phylogenetic family of Asian TSV isolates. The results of this study demonstrated that both mortality and histological lesions are associated with TSV infection in P. monodon.

Amino Acid Sequence↗

PubMed2005

Phylogenetic analysis of Taura syndrome virus isolates collected between 1993 and 2004 and virulence comparison between two isolates representing different genetic variants.

Taura syndrome virus (TSV) is highly pathogenic to Litopenaeus vannamei (Pacific white shrimp) and has caused significant economic loss in the shrimp culture industry. It was first reported from Ecuador in 1992 and has since become widely distributed throughout the Americas and southeast Asia (SE Asia). To determine the genetic relationship among various geographic isolates, we amplified and sequenced a 1.3 kb fragment of the TSV capsid protein gene 2 (CP2) from each of 34 isolates collected from cultured penaeid shrimp stocks in Ecuador, Colombia, Honduras, USA, Mexico, Belize, Thailand, China, and Indonesia. An additional six CP2 sequences obtained from GenBank were included in the analysis. The results indicated low genetic variation (0--5.6% for nucleotide sequence and 0--7.0% for deduced amino acid sequence) among these 40 isolates. A phylogenetic analysis based on the deduced CP2 amino acid sequence revealed three distinct groups: Americas, Belize, and SE Asia. The Belize and SE Asia groups were separated from each other by a 4.7% difference in amino acid sequence. The Belize and Americas groups differed by 4.4%. The Americas and SE Asia groups were the closest, separated by a difference of only 3.3%. Comparison between Belize and Hawaii TSV (reference strain for Americas group) indicated that Belize TSV was more virulent than Hawaii TSV. In bioassays, the Belize isolate caused 50% mortality by 3 days, while the Hawaii isolate caused 50% mortality over 4--6 days. Based on the phylogenetic analysis and virulence comparison, the Belize TSV isolate should be considered as a new variant.

Amino Acid Sequence↗

PubMed2005

Taura syndrome virus from Belize represents a unique variant.

A Taura syndrome virus (TSV) isolate from cultured Penaeus vannamei grown in Belize, Central America was characterized and shown to be a unique isolate. Mortality rates in laboratory infections of specific pathogen-free (SPF) P. vannamei, reactivity of the virus with monoclonal antibody (MAb) 1A1 and phylogenetic analysis demonstrated that the Belize isolate (BLZ02TSV) is a new valiant of TSV. The Hawaiian 1994 TSV isolate (HI94TSV, GenBank AF277675) was used as the reference isolate for these studies. Laboratory infections of SPF P. vannamei with BLZ02TSV demonstrated higher mortalities and earlier onset of mortalities compared to infections with HI94TSV. Shrimp tissues infected with BLZ02TSV reacted with a TSV-specific gene probe by in situ hybridization and were positive by RT-PCR using TSV diagnostic primers, thus indicating that the isolate was TSV. However, Western blot analysis and immunohistochemistry using MAb 1A1 demonstrated that BLZ02TSV did not react with the antibody, suggestive of changes in the VP1 region of the genome that codes for the polypeptide to which MAb 1A1 binds. Phylogenetic analysis of a 1.3 kbp fragment of the TSV VP1 capsid region revealed that BLZ02TSV represents a distinct group among more than 29 isolates of TSV studied thus far. This research demonstrates that BLZ02TSV is a unique isolate of TSV and reiterates a problem related to the use of MAb 1A1 for detection of TSV in clinical specimens.

Amino Acid Sequence↗

PubMed2005

Spiroplasma penaei sp. nov., associated with mortalities in Penaeus vannamei, Pacific white shrimp.

A new bacterial strain, designated SHRIMP(T), isolated from the haemolymph of the Pacific white shrimp, Penaeus vannamei, was serologically distinct from other spiroplasmas. Cells of this strain were helical in form and variable in length. Examination by electron microscopy revealed wall-less cells delineated by a single cytoplasmic membrane. The organisms grew well in M1D media supplemented with 2 % NaCl. Strain SHRIMP(T) grew at temperatures of 20-37 degrees C, with optimum growth occurring at 28 degrees C. The strain catabolized glucose and hydrolysed arginine, but did not hydrolyse urea. The G+C content of the DNA was 29 +/-1 mol%. Strain SHRIMP(T) (=ATCC BAA-1082T=CAIM 1252T) is designated the type strain of a novel species, Spiroplasma penaei sp. nov., which represents a new subgroup (I-9) of the group I spiroplasmas.

Animals↗

PubMed2004

Characterization and molecular methods for detection of a novel spiroplasma pathogenic to Penaeus vannamei.

Traditionally, Spiroplasma spp. have only been isolated from the surfaces of flowers and other plant parts, from the guts and hemolymph of various insects, and from vascular plant fluids (phloem sap) and insects that feed on these fluids. In this article, we report the first pathogenic spiroplasma to be discovered in shrimp and the results of its characterization through histological evaluation, in situ hybridization assays, transmission electron microscopy, 16S rRNA sequence homology, and injection infectivity studies. In addition, molecular methods are described that were developed for the detection of this microorganism, which was determined to be the causative disease agent in Colombian farm-raised Penaeus vannamei suffering from high mortalities. Using standard histological methods and in situ hybridization assays, it was confirmed that P. vannamei was infected with this pathogenic spiroplasma. Histological analysis revealed systemic inflammatory reactions in affected organs/tissues. In an attempt to identify the bacteria, frozen infected P. vannamei samples, from the initial epizootic, were used to sequence the 16S rRNA gene and develop molecular detection methods. The 16S rRNA gene was amplified by PCR and then sequenced. The sequence data were analyzed using the GenBank BLAST search and the results revealed a 98% homology with Spiroplasma citri, a pathogen of citrus trees. The 16S rRNA sequence data were evaluated for development of unique PCR primers to the putative spiroplasma. Using PCR primers developed for the spiralin gene of Spiroplasma spp., a digoxigenin-labeled probe was developed and tested. This probe was species-specific, with no positive reactions or cross-reactivity occurring with other bacterial samples tested in this format.

Animals↗

PubMed2004

Development of monoclonal antibodies for detection of necrotizing hepatopancreatitis in penaeid shrimp.

Monoclonal antibodies (MAbs) were produced against necrotizing hepatopancreatitis bacteria (NHP-B) of penaeid shrimp. The MAbs tested in dot-immunoblot (D-IB) assays were capable of detecting the NHP-B in hepatopancreas samples collected from moribund juvenile Litopenaeus vannamei during an experimentally induced NHP-B infection. The MAbs were also screened by immunohistochemistry (IHC) using case submissions that were determined to be infected not only by histology, but also polymerase chain reaction (PCR) and in situ hybridization (ISH) assays using specific digoxigenin (DIG)-labeled probes on histological sections prepared from naturally infected shrimp. Two of the MAbs were chosen for development of detection methods for NHP. The MAbs were tested using IHC methods on Davidson's alcohol-formalin-acetic acid (AFA) fixed tissue sections and identified NHP-B infected cells and tissues in a pattern similar to that seen with DIG-labeled NHP-specific gene probes. None of the MAbs reacted with tissue from specific pathogen-free (SPF) shrimp or with shrimp tissues infected with a rickettsia-like bacteria, Vibrio sp., Campylobacter sp., and Spiroplasma sp. The MAbs were found to be negative against these other organisms, demonstrating that they are species specific and useful for rapid diagnostic detection of NHP-B.

Animals↗

PubMed2004

Quantitation of Taura syndrome virus by real-time RT-PCR with a TaqMan assay.

A real-time RT-PCR assay was developed using a TaqMan probe to detect and quantify Taura syndrome virus (TSV) in penaeid shrimp. A pair of RT-PCR primers, which amplify a 72 bp DNA fragment, and a TaqMan probe were selected from open reading frame 1 (ORF1) of the TSV genome. The primers and TaqMan probe used in this assay reacted with TSV isolates from Hawaii, Texas, Colombia, Mexico, Belize, Indonesia, and Thailand, but neither with RNA of healthy shrimp nor with an isolate of yellow head virus. A plasmid (pTSV-1) that contains the target TSV sequence was constructed and used to generate positive control RNA through in vitro transcription. The positive control RNA was used to demonstrate that the real-time RT-PCR assay has a detection limit of 100 copies and a log-linear range up to 10(8) copies of TSV RNA. This quantitative method was found to be highly reproducible, with low intra- and inter-assay variation. Coefficient of variation (CVs) values were 0.04-8.9 and 0.05-3.7%, respectively, for replicates within and among assays. This assay was used to quantify TSV in both acutely and chronically infected shrimp in a laboratory experiment. The quantities of TSV in the tissues of pleopods and gills were not significantly different, and there was no difference in TSV levels between the acutely and chronically infected groups. However, in the chronically infected shrimp, the quantities of TSV were one to two orders of magnitude higher in the lymphoid organ than in either gills or pleopods. This assay proved to be specific with high sensitivity, and it can be used to detect and quantify TSV in shrimp samples.

Animals↗

PubMed2004

Nonsusceptibility of primate cells to Taura syndrome virus.

Taura syndrome virus (TSV), a pathogen of penaeid shrimp and member of the family Dicistroviridae, was recently reported to have the ability to infect primate cells. We independently retested this hypothesis. Three lines of primate cells FRhK-4, MA-104, and BGMK, which are highly susceptible to infection by human picornaviruses, were challenged with TSV. Viral replication was assayed by real-time reverse transcription-polymerase chain reaction using cell media samples collected on days 0, 4, and 7 postchallenge. By day 7, genome copy numbers had decreased 25%-99%. No cytopathic effect was observed after 7 days. An in situ hybridization assay, with gene probes specific for detection of TSV, was negative for TSV in challenged cells. The infectivity of residual virus in the cell culture media at day 7 was confirmed by bioassay using TSV-free indicator shrimp (Litopenaeus vannamei). TSV did not infect the primate cells tested, and no evidence of zoonotic potential was found.

Animals↗

PubMed2003

Experimental infection of Penaeus vannamei by a rickettsia-like bacterium (RLB) originating from P. monodon.

A rickettsia-like bacterium (RLB), which caused severe mortalities of commercially farmed Penaeus monodon in the southwest region of Madagascar, was investigated to determine whether the organism would produce the same disease in P. vannamei. Two series of bioassays were performed to determine whether this RLB could be transmitted to P. vannamei through injection and per os exposure. The first series of challenge bioassays used frozen, RLB-infected P. monodon tissue from Madagascar as the inoculum and feed for the injection, and per os bioassays with specific pathogen free (SPF) P. vannamei. In the second series of bioassays, frozen RLB-infected P. vannamei tissue derived from the first series of injection bioassays was used as the inoculum to challenge by injection and per os SPF P. vannamei. Disease status was determined through standard histological techniques and by in situ hybridization assays with a digoxigenin-labeled probe specific for this RLB. The results indicated that P. vannamei did develop the RLB infection when injected with either RLB infected P. monodon or P. vannamei tissue homogenates. This contrasts with results from the per os exposure to the RLB in which the disease could not be reproduced.

Animals↗

PubMed2003

Geographic variations among infectious hypodermal and hematopoietic necrosis virus (IHHNV) isolates and characteristics of their infection.

Nucleotide sequence variations of a 2.9 kb fragment of infectious hypodermal and hematopoietic necrosis virus (IHHNV) isolated from samples of Penaeus monodon were determined and compared with an isolate from Hawaii. The infection characteristics of these isolates were examined by histology, in situ hybridization, and laboratory challenge studies with P. vannamei. Isolates of IHHNV were obtained from samples collected from the SE Asia region (the Philippines, Thailand, and Taiwan). Isolates of putative IHHNV were obtained from African samples (Tanzania, Madagascar, and Mauritius). The Philippine isolate had a very high nucleotide sequence identity (99.8%) to Hawaii IHHNV. The Thailand isolate showed a slightly lower identity (96.2%). The putative IHHNV sequences collected from Tanzania and Madagascar showed greater divergence from Hawaii IHHNV, 8.2% difference for Tanzania and 14.1% difference for Madagascar. A phylogenetic analysis showed that the Philippine IHHNV clustered with IHHNV found in the western hemisphere. This supports the theory that the Philippines was the origin of IHHNV that was first detected in Hawaii. In the laboratory infection study, both the Philippine and Thailand IHHNV were passed into P. vannamei, and the infected shrimp did not suffer any mortalities. In another laboratory infection, P. vannamei injected with a tissue homogenate of P. monodon from Madagascar, which tested positive for IHHNV by PCR, did not demonstrate IHHNV infection, suggesting that this putative IHHNV is not infectious to P. vannamei.

Amino Acid Sequence↗

PubMed2003

Molecular detection methods developed for a systemic rickettsia-like bacterium (RLB) in Penaeus monodon (Decapoda: Crustacea).

Molecular detection methods were developed to aid in the diagnosis of a rickettsia-like bacterium (RLB) which caused severe mortalities of farm-raised Penaeus monodon in Madagascar. Using primers derived from the 16S rRNA gene of bacteria, a PCR assay was optimized to amplify this region of the genome of the RLB, using extracted DNA from infected P. monodon tissue as the template. The resulting amplified PCR product was sequenced and 2 novel primers were selected from the variable region of the gene. These primers amplified a 532 bp fragment of DNA originating from the rickettsia-infected samples. The PCR assay was optimized and tested on DNA extracted from specific pathogen-free (SPF) P. vannamei tissue and several other strains of bacteria. The PCR assay with the rickettsia-specific primers was specific for this RLB and did not amplify the other DNA samples tested. The 532 bp PCR-amplified fragment was labeled with digoxigenin (DIG) for in situ hybridization assays. This probe was tested on SPF, RLB and bacteria-infected shrimp specimens preserved in Davidson's fixative. The probe was specific for both natural and experimental rickettsial infections. Hybridization with this probe required a stringent temperature of 65 degrees C, otherwise cross-reactivity was observed with other types of bacteria.

Animals↗

PubMed2002

Detection of Taura syndrome virus (TSV) strain differences using selected diagnostic methods: diagnostic implications in penaeid shrimp.

Anecdotal industry reports of Taura syndrome (TS) epizootics in a Taura syndrome virus (TSV) tolerant strain of Penaeus stylirostris and collected evidence of field TS epizootics in P. stylirostris suggested that a distinct new TSV strain might have emerged since 1994. The Ecuadorian 1992 TSV genome published in GenBank is virtually identical to the Hawaiian 1994 TSV isolate (HI94TSV) used as reference throughout this investigation. Three other geographic and year isolates of TSV from naturally occurring TS epizootics of cultured penaeid shrimp were obtained from Mexico (SIN98TSV and MX99TSV from P. vannamei and SON2KTSV from P. stylirostris). Selected TSV diagnostic methods set forth by the Office International des Epizooties were utilized as the basis for isolate analysis. By Southern blot, TSV probes P15 and Q1 reacted specifically with all the diagnostic reverse transcription polymerase chain reaction (RT-PCR) fragments. Additionally, labeled RT-PCR amplicons from the TSV isolates amplified by routine diagnostic RT-PCR primers gave positive in situ hybridizations with TSV, indicating that all 4 isolates shared homology. By Western blot, immuno-dot blot, and immunohistochemistry, all TSV-purified isolates reacted with TSV polyclonal antibody (PAb). However, with TSV monoclonal antibody (MAb) 1A1 all isolates, except SIN98TSV, reacted, indicating that the difference in isolate SIN98TSV is within VP1, the target for MAb 1A1. The amino acid (AA) sequence of SIN98TSV VP1, MX99TSV VP1 and SON2KTSV VP1 has a 98% homology with the reference HI94TSV VP1. A span of 12 AAs are identified in SIN98TSV VP1 containing significant AA substitutions which may account for a conformational change of the antigenic epitope sufficient to prevent MAb 1A1 from binding. The implications of these results with respect to the antibody-based diagnosis of TSV are discussed.

Amino Acid Sequence↗

PubMed2002

Low sequence variation among isolates of infectious hypodermal and hematopoietic necrosis virus (IHHNV) originating from Hawaii and the Americas.

A 2.9 kb fragment of the infectious hypodermal and hematopoietic necrosis virus (IHHNV) genome, which contains the coding sequence of putative non-structural and capsid proteins, was amplified and sequenced from each of 14 IHHNV isolates collected from cultured penaeid shrimp stocks in Hawaii and various sites in the Americas between 1982 and 1997. The sequence comparison indicates that the IHHNV genome is very stable, with 99.6 to 100% similarity among these 14 isolates. Only nucleotide substitutions were found. The percentage of substitution was higher in the putative capsid proteins region (1.3%) than in the putative non-structural proteins region (0.6%). Out of 25 substitutions found, 14 resulted in amino acid changes. There is no apparent association between clinical outcomes and particular amino acid substitutions. Based on genetic distances, the isolates were clustered into 3 groups that generally correspond with their geographic origins.

Animals↗