Characterization of beta-cell function of pancreatic islets isolated from bank voles developing glucose intolerance/diabetes: an animal model showing features of both type 1 and type 2 diabetes mellitus, and a possible role of the Ljungan virus

Bank voles (Clethrionomys glareolus) kept in captivity develop diabetes mellitus to a significant extent. Also in wild bank voles, elevated blood glucose has been observed. A newly isolated picornavirus named Ljungan virus (LV) has been found in the pancreas of these bank voles. Moreover, LV infection in combination with environmental factors may cause glucose intolerance/diabetes (GINT/D) in normal mice. The aim of the present study was to investigate the functional characteristics of pancreatic islets, isolated from bank voles, bred in the laboratory but considered LV infected. About 20% of all males and females were classified as GINT/D following a glucose tolerance test. Of these animals the majority had become diabetic by 20 weeks of age, with a tendency towards an earlier onset in the males. GINT/D animals had increased serum insulin levels. Islets were tested on the day of isolation (day 0) and after 1 week of culture for their insulin content and their capacity to synthesize (pro)insulin, secrete insulin and metabolize glucose. Functional differences could be observed between normal and GINT/D animals as well as between genders. An elevated basal insulin secretion was observed on day 0 indicating beta-cell dysfunction among islets isolated from diabetic males. In vitro culture could reverse some functional changes. The increased serum insulin level and the increased basal islet insulin secretion may suggest that the animals had developed a type 2 diabetes-like condition. It is likely that the putative stress imposed in the laboratory, maybe in combination with LV infection, can lead to an increased functional demand on the beta-cells.

Phenology, distribution, and host specificity of Solenopsis invicta virus-1

Studies were conducted to examine the phenology, geographic distribution, and host specificity of the Solenopsis invicta virus-1 (SINV-1). Two genotypes examined, SINV-1 and -1A, exhibited similar seasonal prevalence patterns. Infection rates among colonies of S. invicta in Gainesville, Florida, were lowest from early winter (December) to early spring (April) increasing rapidly in late spring (May) and remaining high through August before declining again in the fall (September/October). Correlation analysis revealed a significant relationship between mean monthly temperature and SINV-1 (p<0.0005, r=0.82) and SINV-1A (p<0.0001, r=0.86) infection rates in S. invicta colonies. SINV-1 was widely distributed among S. invicta populations. The virus was detected in S. invicta from Argentina and from all U.S. states examined, with the exception of New Mexico. SINV-1 and -1A were also detected in other Solenopsis species. SINV-1 was detected in Solenopsis richteri and the S. invicta/richteri hybrid collected from northern Alabama and Solenopsis geminata from Florida. SINV-1A was detected in S. geminata and Solenopsis carolinensis in Florida and the S. invicta/richteri hybrid in Alabama. Of the 1989 arthropods collected from 6 pitfall trap experiments from Gainesville and Williston, Florida, none except S. invicta tested positive for SINV-1 or SINV-1A. SINV-1 did not appear to infect or replicate within Sf9 or Dm-2 cells in vitro. The number of SINV-1 genome copies did not significantly increase over the course of the experiment, nor were any cytopathic effects observed. Phylogenetic analyses of SINV-1/-1A nucleotide sequences indicated significant divergence between viruses collected from Argentina and the U.S.

Recent Korean isolates of duck hepatitis virus reveal the presence of a new geno- and serotype when compared to duck hepatitis virus type 1 type strains

Duck hepatitis was first reported in 1985 in Korea. The complete nucleotide sequence of two past Korean isolates, DHV-HS and DHV-HSS, isolated in 1994 and 1995, and four recent Korean isolates, AP-03337, AP-04009, AP-04114 and AP-04203 isolated in 2003 and 2004, were determined. Phylogenetic analysis using the 3D protein sequence confirmed that the previously characterized duck hepatitis virus type 1 strains and the six Korean isolates described here constitute a monophyletic group and form two clades/genotypes in which all except the four recent Korean isolates form one group (A) and the recent Korean isolates of 2003 and 2004 constitute a second group (B). Phylogenetic analysis of the VP1 protein supported the division into two different groups. Antisera raised against viruses of group A showed significant neutralizing cross-reaction against a member of the same genotype but not to a strain of group B and vice versa. These results demonstrated that the two genotypes also could be regarded as two different serotypes.

Detection of viruses in nasal swab samples from horses with acute, febrile, respiratory disease using virus isolation, polymerase chain reaction and serology

OBJECTIVE

To examine the association of viruses with acute febrile respiratory disease in horses. Design Nasal swab and serum samples were collected from 20 horses with acute febrile upper respiratory disease that was clinically assessed to have a viral origin.

METHODS

Each of the samples was inoculated onto equine fetal kidney, RK13 and Vero cell cultures, and viral nucleic acid was extracted for polymerase chain reaction (PCR) or reverse transcription PCR. PCR primers were designed to amplify nucleic acid from viruses known to cause or be associated with acute febrile respiratory disease in horses in Australia. A type specific ELISA was used to measure equine herpesvirus (EHV1 and EHV4) antibody, and serum neutralisation assays were used to measure equine rhinitis A virus (ERAV) and equine rhinitis B virus 1 and 2 (ERBV1 and ERBV2) antibody titres in serum samples.

RESULTS

Virus was isolated from 4 of 20 nasal swab samples. There were three isolations of EHV4 and one of ERBV2. By PCR, virus was identified in the nasal swab samples of 12 of the 20 horses. Of the 12 horses [corrected] that were positive, 17 viruses were detected as follows: there was [corrected] one triple positive (EHV4, EHV2, and EHV5), three double positives (EHV4, ERBV and EHV5, ERBV (2 horses)) and 8 [corrected] single positives (EHV4 (2 horses), EHV5 (3 horses) and ERBV (3 [corrected] horses).

CONCLUSION

By virus isolation and PCR, 17 viruses were identified in nasal swab samples from 12 of 20 horses that had acute febrile respiratory disease consistent with a diagnosis of virus infection. Initial PCR identification and subsequent virus isolation led to the isolation of ERBV2 for the first time in Australia and the second time anywhere of ERBV2.

Molecular characterization of a new serotype of duck hepatitis virus

Duck hepatitis strains 90D and 04G were determined to be antigenically unrelated to type 1 duck hepatitis virus (DHV-1) by in vitro cross-neutralization assay. The genome sequences of 90D and 04G revealed that both strains of the new serotype DHV (N-DHV) possessed a typical picornavirus genome organization apart from the unique possession of three in-tandem 2A genes present in DHV-1. The 2A1, 2A2, and 2A3 proteins represented an aphthovirus-like 2A protein, AIG1-like protein, and human parechovirus-like 2A protein, respectively. The N-DHV genome displayed unique features, compared to the DHV-1 genome. The 366 nt 3'UTR of N-DHV, the largest determined thus far among picornaviruses, was 52 nt longer than DHV-1. The pairwise percent identity of the nucleic acid and amino acid sequences at 1D region of N-DHV and DHV-1 were only 69.1-69.7 and 70.1-70.5%, respectively. Finally, phylogenetic and evolutionary analysis of N-DHV revealed that the N-DHV and DHV-1 belong to two different clusters of a novel genus in the Picornaviridae family.

Prevalence of serum neutralising antibody to equine rhinitis A virus (ERAV), equine rhinitis B virus 1 (ERBV1) and ERBV2

The objective of this study was to determine the incidence of serum neutralising (SN) antibody to ERAV, ERBV1 and ERBV2 in a population of horses from birth to 22 years of age. The prevalences of ERAV, ERBV1 and ERBV2 SN antibodies in 381 sera obtained from 291 horses were 37%, 83% and 66%, respectively. ERAV, ERBV1 and ERBV2 maternal antibody was present in foals 12 h postsuckling but by 10-12 months, ERAV SN antibody was not detected in any of the horses, while ERBV1 and ERBV2 SN antibodies were common (83% and 100%, respectively). Sera were obtained from 44 Thoroughbred horses when they were newly introduced into a training centre when their average age was 23 months and a second sample was obtained approximately 7 months later. ERAV SN antibody was present in 8 (18%) when first bled and in 27 (61%) when tested 7 months later. Accordingly 19 of the 44 horses (43%) seroconverted to ERAV within 7 months of entering the training stable. Among all the horses the average ERAV SN antibody titre was relatively high (3796) and in contrast, ERBV1 and ERBV2 titres were relatively low (average 84 and 45, respectively) and often fell to below detectable levels over time and at a rate comparable to new seroconversions in the same group of horses.

Reverse transcriptase-polymerase chain reaction for the detection equine rhinitis B viruses and cell culture isolation of the virus

Equine rhinitis B virus (ERBV), genus Erbovirus, family Picornaviridae occurs as two serotypes, ERBV1 and ERBV2. An ERBV-specific nested reverse transcriptase-polymerase chain reaction (RT-PCR) that amplified a product within the 3D(pol) and 3' non-translated region of the viral genome was developed. The RT-PCR detected all 24 available ERBV1 isolates and one available ERBV2 isolate. The limit of detection for the prototype strain ERBV1.1436/71 was 0.1 50% tissue culture infectious doses. The RT-PCR was used to detect viral RNA in six of 17 nasopharyngeal swab samples from horses that had clinical signs of acute febrile respiratory disease but from which ERBV was not initially isolated in cell culture. The sequences of these six ERBV RT-PCR positive samples had 93-96% nucleotide identity with six other partially sequenced ERBV1 isolates and one ERBV2. ERBV was isolated from one of the six samples at fourth cell culture passage when it was shown that the addition of 20 mg/mL MgCl(2) to the cell culture medium enhanced the growth of the virus. This isolated virus was antigenically similar to ERBV2.313/75. Determination of the nucleotide sequence of the P1 region of the genome also indicated that the isolate was ERBV2, and it was therefore designated ERBV2.1576/99. This is the first reported isolation of ERBV in Australia. The study highlights the utility of PCR for the identification of viruses in clinical samples that may initially be considered negative by conventional cell culture isolation.

Isolation and molecular characterization of a porcine teschovirus 1 isolate from China

Porcine teschovirus 1 (PTV-1) (Swine/CH/IMH/03) was isolated from piglets in a farm in Inner Mongolia Province, P.R. China. It was confirmed by electron microscopy, RT-PCR, and sequencing. Comparison of the sequences of the amino acid and nucleotides and phylogenetic analysis of the polyprotein showed that PTV Swine/CH/IMH/03 strain is PTV-1. The isolated virus has closest relationship with Talfan strain, they shared 98.9% and 99.5% homology of amino acids and nucleotides, respectively, in the ORF of polyprotein. To our knowledge, this is the first report about isolation and identification of a PTV in China.

Validation of RT-PCR Assays for Molecular Characterization of Porcine Teschoviruses and Enteroviruses

Porcine enteroviruses (PEVs) and teschoviruses (PTVs) are described as causative agents of neurological disorders, fertility disorders and dermal lesions of swine. Difficulties in the serological detection of these viruses may lead to a significant underestimation of infections with clinical symptoms. With the recent availability of genome sequence data for all the serotypes, molecular diagnosis is a possibility. The present study describes a new approach to molecular 'serotyping' of PTVs and PEV-B viruses, involving the amplification and sequencing of a genomic fragment of the VP1 coding region. A molecular characterization of Italian entero-teschovirus isolates was performed using a set of previously published and newly designed polymerase chain reaction primers. A total of 33 porcine isolates and 10 reference strains were analysed. Porcine enterovirus-B samples were first diagnosed as positive for enterovirus by amplification of the 5'-non-translated region. Samples were then typed by amplification and sequencing of a portion of the VP1 coding region. Porcine enterovirus-A and PTVs were detected by a published assay in the 5'-NC region that allows them to be differentiated according to the size of amplification product, using the same set of primers. For serotype characterization of PTV, we evaluated four different regions: the N terminus of the capsid protein VP2, the region encoding for RNA-dependent RNA polymerase, and the capsid VP1 and VP4 regions. The newly designed primers in the VP1 region was proved to be broad in range and suitable for serotype assessment and therefore constitute a useful diagnostic tool for molecular diagnosis of porcine teschovirus/enterovirus strains and for the study of molecular epidemiology and evolution of these viruses.

Diabetes and myocarditis in voles and lemmings at cyclic peak densities--induced by Ljungan virus?

Although it is well-documented from theoretical studies that pathogens have the capacity to generate cycles, the occurrence and role of pathogens and disease have been poorly empirically studied in cyclic voles and lemmings. In screening for the occurrence of disease in cyclic vole and lemming populations, we found that a high proportion of live-trapped Clethrionomys glareolus, C. rufocanus, Microtus agrestis and Lemmus lemmus at high collective peak density, shortly before the decline, suffered from diabetes or myocarditis in northern Scandinavia. A high frequency of animals had abnormal blood glucose (BG) levels at the time of trapping (5-33%). In contrast, C. rufocanus individuals tested at a much lower overall density, and at an earlier stage relative to the decline in the following cycle, showed normal BG concentrations. However, a high proportion (43%) of a sample of these individuals kept in captivity developed clinical diabetes within five weeks, as determined by BG levels and a glucose tolerance test performed at that later time. A new picornavirus isolated from the rodents, Ljungan virus (LV), was assumed to cause the diseases, as LV-induced diabetes and myocarditis, as well as encephalitis and fetal deaths, were observed in laboratory mice. We hypothesize that LV infection significantly affects morbidity and mortality rates in the wild, either directly or indirectly, by predisposing the rodents to predation, and is at least involved in causing the regular, rapid population declines of these cyclic voles and lemmings. Increased stress at peak densities is thought to be an important trigger for the development of disease, as the occurrence of disease in laboratory mice has been found to be triggered by introducing stress to LV-infected animals.

Evaluation of the efficacy of a live fowlpox-vectored infectious laryngotracheitis/avian encephalomyelitis vaccine against ILT viral challenge

Infectious laryngotracheitis (ILT) is caused by an alphaherpesvirus, and latency can be produced by previous exposure to vaccine virus. The main sites of latency for the ILT virus have been shown to be the trigeminal ganglion and the trachea. Reactivation of latent virus is one factor related to the production of clinical signs. The development of a genetically engineered ILT vaccine has been suggested for many years as a tool to eliminate viral latency. Several approaches have been suggested. Included among them is the development of a thymidine kinase-deficient mutant or the insertion of ILT viral glycoproteins into a viral vector such as a poxvirus. A commercially available, live, fowlpox-vectored infectious laryngotracheitis + avian encephalomyelitis (FP-LT+AE) vaccine was used in field trials in leghorn pullet flocks and evaluated by tracheal challenge in a laboratory setting with the use of the National Veterinary Services Laboratory (Ames, IA) ILT challenge virus. Interference of the pigeon pox vaccine, which is often administered concurrently with fowlpox vaccine, was also evaluated when given in conjunction with the FP-LT+AE vaccine. Overall, the results indicate that the FP-LT+AE vaccine provides adequate protection against ILT viral challenge. Proper administration is essential. In one flock, inadequate protection was most likely a result of either poor vaccine administration or previous exposure to pox virus. In addition, the simultaneous administration of pigeon pox vaccine did not appear to interfere with protection against ILT viral challenge.

Several recombinant capsid proteins of equine rhinitis a virus show potential as diagnostic antigens

Equine rhinitis A virus (ERAV) is a significant pathogen of horses and is also closely related to Foot-and-mouth disease virus (FMDV). Despite these facts, knowledge of the prevalence and importance of ERAV infections remains limited, largely due to the absence of a simple, robust diagnostic assay. In this study, we compared the antigenicities of recombinant full-length and fragmented ERAV capsid proteins expressed in Escherichia coli by using sera from experimentally infected and naturally exposed horses. We found that, from the range of antigens tested, recombinant proteins encompassing the C-terminal region of VP1, full-length VP2, and the N-terminal region of VP2 reacted specifically with antibodies present in sera from each of the five experimentally infected horses examined. Antibodies to epitopes on VP2 (both native and recombinant forms) persisted longer postinfection (>105 days) than antibodies specific for epitopes on other fragments. Our data also suggest that B-cell epitopes within the C terminus of VP1 and N terminus of VP2 contribute to a large proportion of the total reactivity of recombinant VP1 and VP2, respectively. Importantly, the reactivity of these VP1 and VP2 recombinant proteins in enzyme-linked immunosorbent assays (ELISAs) correlated well with the results from a range of native antigen-based serological assays using sera from 12 field horses. This study provides promising candidates for development of a diagnostic ERAV ELISA.

Prevalence of neutralizing antibodies to Equine rhinitis A and B virus in horses and man

Equine rhinitis viruses (ERVs) are the causative agents of mild to severe upper respiratory infections in horses worldwide. Immunologically, four serotypes of ERVs have been identified. Equine rhinitis A virus (ERAV) and Equine rhinitis B virus 1 (ERBV1) are the most frequent serotypes in Europe. Both viruses have a broad host range in cultured cells with ERAV being able to infect humans. Since there is neither information on the seroprevalence of ERAV and ERBV1 in Austria nor on the zoonotic potential of ERBV1, we investigated 200 horse and 137 veterinary sera for the presence of neutralizing antibodies relating to ERAV and ERBV1. One hundred and eighty (90%) and 173 (86%) horse sera neutralized ERAV and ERBV1, respectively. In contrast, only four (2.7%) and five (3.6%) human sera showed weak neutralizing activity to ERAV and ERBV1, respectively. These results indicate that ERAV and ERBV1 are widespread in the Austrian horse population; however, the risk of acquiring zoonotic infection among veterinarians appears low.

Avian encephalomyelitis in naturally infected pigeons in Turkey

The pathological and immunohistochemical findings of avian encephalomyelitis (AE) were described in various tissues of naturally infected pigeons of a flock from a outbreak in Turkey. Clinically, paresis, paralysis, circling movement and torticollis of the head associated with nervous signs were marked symptoms among the diseased pigeons. At necropsy, small or large white-greyish foci were detected in the pancreas, and erosive-ulcerative foci along with petechial hemorrhages in ingluves. Histopathologically, lesions in central nervous system, particularly in the cerebellum molecular layer, consisted of non-suppurative encephalomyelitis. Lesions in the pancreas revealed non-suppurative pancreatitis along with acinar degeneration and necrosis and/or lymphoid aggregations. Immunohistochemical staining of formalin-fixed, paraffin-embedded tissues was performed using a direct-fluorescein antibody technique with chicken anti-AE virus serum fluorescein isothiocyanate conjugate. Viral antigen was strongly stained in cytoplasm of epithelial cells of the exocrine glands, and neurons of the cerebral hemispheres and midbrain. In addition, viral antigen was also marked in the kidneys and tissues of the digestive system. Consequently, this article is, to our knowledge, the first report of natural AE in pigeons.

Identification of a neutralizing epitope in the βE–βF loop of VP1 of equine rhinitis A virus, defined by a neutralization-resistant variant

Equine rhinitis A virus strain 393/76 (ERAV.393/76) was passaged in the presence of post-infection ERAV.393/76 equine polyclonal antiserum (EPA). Viruses with increased resistance to neutralization by EPA were obtained after 15 passages. Compared with the parent virus, five plaque-purified, neutralization-resistant mutant viruses, in addition to the non-plaque-purified viruses that were examined, had a Glu→Lys change at position 658, which is located in the predicted βE–βF (EF) loop of VP1. Rabbit antiserum was prepared against the isolated EF loop of ERAV.393/76 VP1 expressed as a fusion protein with glutathione S-transferase. This antiserum bound to purified ERAV.393/76 in Western blots, but not to the neutralization-resistant mutant virus or to ERAV.PERV/62, a naturally occurring ERAV strain that has a Lys residue at position 658. These results suggest that the EF loop of VP1 is involved in a neutralization epitope of ERAV.

Teschoviruses as indicators of porcine fecal contamination of surface water

Teschoviruses specifically infect pigs and are shed in pig feces. Hence, their presence in water should indicate contamination with pig fecal residues. To assess this hypothesis, we have developed a real-time reverse transcriptase PCR (RT-PCR) method that allows the quantitative detection of pig teschovirus (PTV) RNA. The method is able to detect 92 fg of PTV RNA per ml of sample. Using this method, we have detected the presence of PTV RNA in water and fecal samples from all pig farms examined (n = 5). Feces from other animal species (cattle, sheep, and goats) were negative in this test. To compare the PTV RNA detection method with conventional chemical determinations currently in use for evaluation of water contamination, we analyzed water samples collected downstream from a pig slurry spillage site. We have found a positive correlation within both types of determinations. The sensitivity of the PTV detection assay was similar to that achieved by unspecific organic matter determination and superior to all other conventional chemical analyses performed. Furthermore, the new method is highly specific, revealing the porcine origin of the contamination, a feature that is lacking in currently available methods for the assessment of water contamination.

Detection of porcine teschoviruses and enteroviruses by LightCycler real-time PCR

Porcine picornaviruses comprising at least 23 serotypes grouped into six species were described as causative agents of neurological disorders, reproductive failure, and aphthae-like dermal lesions of swine. Other viruses such as classical swine fever virus (CSFV), African swine fever virus, pseudorabies virus (PRV), vesicular stomatitis virus, vesicular exanthema virus, porcine respiratory and reproductive syndrome virus, and porcine parvovirus (PPV) may cause diseases with similar clinical symptoms. Therefore, rapid and reliable PCR detection of the most frequent porcine picornaviruses is of interest. A real-time RT-PCR protocol employing LightCycler technology to detect all known serotypes of the three porcine enterovirus (PEV) cytopathic effect (CPE) groups was established. It uses three sets of primer pairs and group-specific hybridisation probes. The primer pairs were designed to amplify highly conserved sequences of the 5'-non-translated region (5'-NTR) of the relevant virus species. The one-step real-time PCR based on the LightCycler technology is more rapid and less contamination-prone than the nested RT-PCR and allows the precise quantitation of the virus load in the tested specimens. All acknowledged serotypes of the three PEV CPE groups and all tested field strains isolated from clinical specimens were detectable. Viruses of the PEV CPE group III can be distinguished from the closely related swine vesicular disease virus (SVDV).

A case control study of factors and infections associated with clinically apparent respiratory disease in UK Thoroughbred racehorses

A matched case control study was used to determine infections and other factors associated with clinically apparent respiratory disease in young racehorses in training in the UK. A total of 170 cases, defined as horses with sudden onset coughing, nasal discharge or pyrexia, were identified and matched to 632 non-affected controls by trainer and time period. Factors examined included age, sex, time since entry into the training yard, time since last race and different infections including tracheal and nasopharyngeal (NP) bacteria and viruses. Multivariable conditional logistic regression (CLR) modelling was used to evaluate the risk of being a case for variables after adjustment for other factors. Three analyses were conducted using clinical cases as outcomes, which were compared with: (i) controls without evidence of subclinical inflammatory airway disease (IAD) (ii) controls with evidence of subclinical IAD and (iii) all controls irrespective of IAD status. A fourth analysis was conducted comparing the two groups of controls, i.e. those with and without IAD. Younger horses and those that had entered training more recently were at increased risk of suffering episodes of clinically apparent respiratory disease. Among the infections, increasing numbers of Pasteurella/Actinobacillus spp. in tracheal washes were associated with increasing risk of clinical disease. Tracheal infection with Streptococcus zooepidemicus was associated with both clinical respiratory disease and subclinical IAD when compared with controls with no evidence of IAD. This explained the lack of association between clinical cases and S. zooepidemicus when all controls were used. Tracheal isolation of Mycoplasma felis was also associated with clinical disease after controlling for other factors. An inverse association was identified between risk of clinically apparent disease and isolation from tracheal washes of the transient, non-pathogenic bacteria Staphylococcus and Acinetobacter spp. There was no significant association identified between clinical disease and infection with equine herpesviruses-1 and -4, rhinoviruses-1 and -2 or adenovirus. Equine influenza was significantly associated with clinical respiratory disease but it was a very rare infection in this well-vaccinated population, only occurring in three cases.

Mapping epitopes in equine rhinitis A virus VP1 recognized by antibodies elicited in response to infection of the natural host

Equine rhinitis A virus (ERAV) is an important respiratory pathogen of horses and is of additional interest because of its close relationship and common classification with foot-and-mouth disease virus (FMDV). As is the case with FMDV, the VP1 capsid protein of ERAV has been shown to be a target of neutralizing antibodies. In FMDV VP1, such antibodies commonly recognize linear epitopes present in the betaG-betaH loop region. To map linear B cell epitopes in ERAV VP1, overlapping fragments spanning its length were expressed in Escherichia coli as glutathione S-transferase (GST) fusion proteins. These fusion proteins were tested for reactivity with sera from ERAV-infected horses and with polyclonal sera from ERAV-immunized rabbits and mice. Regions at the N- and C-termini as well as the betaE-betaF and the betaG-betaH loop regions contained B cell epitopes that elicited antibodies in the natural host. GST fusion proteins of these regions also elicited antibodies following immunization of rabbits and mice, which, in general, strongly recognized native ERAV VP1 but which were non-neutralizing. It is concluded that the N-terminal region of ERAV VP1, in particular, contains strong B cell epitopes.

A model of Taura syndrome virus (TSV) epidemics in Litopenaeus vannamei

Taura syndrome virus (TSV) is a highly virulent pathogen of Litopenaeus vannamei, has affected shrimp aquaculture throughout the world, and threatens wild populations. Despite its importance, little work has been done on the pathogen's formal epidemiology. Therefore we developed a compartment model for epidemics of TSV in closed populations of L. vannamei. The model includes five compartments, uninfected susceptible, prepatently infected, acutely infected, chronically infected, and dead infected shrimp. The transmission coefficients, patency coefficient, virulence coefficients, and removal coefficient (disappearance of dead infected shrimp) control the dynamics of the model. We estimated the coefficients in laboratory studies and inserted the estimates in the model to characterize TSV epidemics and to estimate the basic reproduction ratio R(0) and threshold density for TSV epidemics in L. vannamei. Further we examined through computer simulation the effect of varying the coefficients on R(0). Decreases in transmission decrease R(0), decreases in virulence increase R(0), increases in patency do not affect R(0), and increases in recovery most likely increase R(0) but under some conditions might decrease it.

Haemolymph parameters of Pacific white shrimp (Litopenaeus vannamei) infected with Taura syndrome virus

Pacific white shrimp (Litopenaeus vannamei) were injected with Taura syndrome virus (TSV) to assess shrimp immune responses and survival. TSV-infected shrimp suffered high mortality, but mock-infected and untreated shrimp experienced no mortality. Moribund shrimp were a pale, reddish colour and were lethargic and soft-shelled. Their haemolymph was clear red and coagulated poorly. In TSV-infected shrimp, the total haemocyte count (THC), hyalinocyte and granulocyte counts, and total plasma protein decreased significantly to 21%, 24%, 17% and 56% of untreated control values, respectively. Haemocyanin decreased to 67%, and clottable proteins to 80% of control values (P< 0.01). Copper and calcium ions, haemocytic transglutaminase (TGase) activity and plasma growth inhibitory activity against Vibrio harveyi also decreased significantly. Generation of intrahaemocytic superoxide anion, O(-2), in TSV-infected shrimp was significantly greater (P< 0.05) than in both control groups, no matter whether glucan stimulated or unstimulated. But the relative increase of intrahaemocytic O(-2) generation in TSV-infected shrimp response to glucan stimulation was lower in both controls. Plasma phenoloxidase (PO) activity increased significantly in TSV-infected shrimp. The plasma bacterial agglutinin titre against E. coli and V. harveyi, growth inhibition of E. coli and the concentration of magnesium ions in TSV-infected shrimp did not change significantly. In conclusion, ten of thirteen haemolymph parameters changed significantly during the host-TSV interaction. These parameters might be valuable references of shrimp health status.

Serologic survey of selected viral, bacterial, and protozoal agents in captive and free-ranging ungulates from central Kenya

Serologic evidence of exposure to various disease agents in free-ranging and captive ungulates at a private game ranch in Kenya is presented, and seroprevalence values inside a fenced-in area are compared with those found on the adjacent open savanna. Zebras outside the fence had a higher prevalence of equine rhinovirus-1 than zebras inside (Fisher's exact test, P = 0.007); for all other species and all other agents, there was no such difference (P > 0.10). Results highlight possible transmission of these agents from domestic species into wildlife or vice versa at our study site.

Equine rhinitis B virus: a new serotype

Equine rhinovirus serotype 3 isolate P313/75 was assigned, with an unclassified genus status, to the family PICORNAVIRIDAE: The sequence from the 5' poly(C) tract to the 3' poly(A) tract of P313/75 was determined. The sequence is 8821 bases in length and contains a potential open reading frame for a polyprotein of 2583 amino acids. Sequence comparison and phylogenic analysis suggest that P313/75 is most closely related to the prototype equine rhinitis B virus (ERBV) strain P1436/71, formerly named equine rhinovirus type 2. A high degree of sequence similarity was found in the P2 and P3 regions of the two genomes. However, the deduced amino acid sequences of the P1 region of P313/75 and ERBV strain P1436/71 contained significant differences, which presumably account for the serological segregation of the two viruses. It is suggested that P313/75 can be classified as a new serotype of the genus Erbovirus, tentatively named ERBV2. Seroepidemiological data indicate that ERBV2 infection of horses may be common (24%) in Australia.

Nucleotide sequence of 3'-end of the genome of Taura syndrome virus of shrimp suggests that it is related to insect picornaviruses

Taura syndrome disease, caused by Taura syndrome virus (TSV), is one of the most important viral diseases of penaeid shrimp in the Western Hemisphere resulting in catastrophic disease epidemics in farmed shrimp. We have cloned and sequenced a 3278 bp cDNA representing the 3' end of the TSV genome. Sequence analyses revealed that frame + 2 had the longest open reading (ORF) frame. This frame contained a 5'-terminal 19 non-coding bases followed by an ORF from nucleotides 20 to 3053 (encoding 1011 amino acids, aa) and a 3' untranslated region of 225 nts. The deduced aa sequence of TSV showed significant similarities with those of the coat proteins of insect picornaviruses, Rhopalosiphum padi virus, Plautia stali intestine virus, Drosophila C virus, Triatoma virus of Triatoma infestans and Himetobi P virus of brown plant hopper. A single transcript of approximately 10 kb was detected by Northern blot hybridization suggesting that the TSV coat protein gene is not expressed as a subgenomic RNA. We concluded that the genome organization of TSV is similar to insect picornaviruses. This is the first molecular evidence of occurrence of a picornavirus in the class Decapoda.