Aspects of the epizootiology of pancreas disease in farmed Atlantic salmon Salmo salar in Ireland.
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A computerised database containing information on over 17.8 million salmon contained within 49 separate marine populations was used to study the epidemiology of pancreas disease (PD) in Ireland. Of the 43 recorded PD outbreaks, 57% occurred in the 3 mo period August to October inclusive (17 to 32 wk post-transfer). Analysis of variance of mortality rates during PD outbreaks occurring on 6 marine sites over a 5 yr period showed that mortality rates vary significantly between sites (p < 0.001) but not between years over this time period. The mortality rate during PD outbreaks ranged from 0.1 to 63%. Mortality rates were significantly higher when PD outbreaks occurred earlier in the year (y = -1.28x + 59, SE of b 0.33). The mean length of a PD outbreak was 112 d (SE = 7.7, n = 37). There was no correlation between PD mortality rate and smolt input weight, initial stocking density and transfer mortality. (+info)
Epidemic O'Nyong-Nyong fever in southcentral Uganda, 1996-1997: entomologic studies in Bbaale village, Rakai District.
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Entomologic studies were conducted between January 27 and February 2, 1997, in Bbaale village in southcentral Uganda during an o'nyong-nyong (ONN) virus epidemic, which began in mid 1996 and continued into 1997. The objectives were to confirm the role of anophelines in ONN virus transmission and to examine other mosquito species as epidemic vectors of ONN virus. Of 10,050 mosquitoes collected using light traps and pyrethrum knockdown sprays, Anopheles (Cellia) funestus Giles was presumed to be the principal vector because it was the most abundant mosquito species from which a strain of ONN virus was isolated. This virus was isolated for the first time from a culicine species, Mansonia (Mansonioides) uniformis Theobald. Bwamba virus and Nyando virus were also isolated from An. funestus. (+info)
Determination of natural versus laboratory human infection with Mayaro virus by molecular analysis.
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A laboratory worker developed clinical signs of infection with Mayaro virus (Togaviridae), an arbovirus of South and Central America, 6 days after preparation of Mayaro viral antigen and 10 days after a trip to a rain forest. There was no evidence of skin lesions during the antigen preparation, and level 3 containment safety measures were followed. Therefore, molecular characterization of the virus was undertaken to identify the source of infection. RT-PCR and DNA sequence comparisons proved the infection was with the laboratory strain. Airborne Mayaro virus contamination is thus a hazard to laboratory personnel. (+info)
Standardization of immunoglobulin M capture enzyme-linked immunosorbent assays for routine diagnosis of arboviral infections.
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Immunoglobulin M antibody-capture enzyme-linked immunosorbent assay (MAC-ELISA) is a rapid and versatile diagnostic method that readily permits the combination of multiple assays. Test consolidation is especially important for arthropod-borne viruses (arboviruses) which belong to at least three virus families: the Togaviridae, Flaviviridae, and Bunyaviridae. Using prototype viruses from each of these families and a panel of well-characterized human sera, we have evaluated and standardized a combined MAC-ELISA capable of identifying virus infections caused by members of each virus family. Furthermore, by grouping antigens geographically and utilizing known serological cross-reactivities, we have reduced the number of antigens necessary for testing, while maintaining adequate detection sensitivity. We have determined that a 1:400 serum dilution is most appropriate for screening antiviral antibody, using a positive-to-negative ratio of >/=2.0 as a positive cutoff value. With a blind-coded human serum panel, this combined MAC-ELISA was shown to have test sensitivity and specificity that correlated well with those of other serological techniques. (+info)
A dual infection of infectious salmon anaemia (ISA) virus and a togavirus-like virus in ISA of Atlantic salmon Salmo salar in New Brunswick, Canada.
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Two viruses, infectious salmon anaemia (ISA) virus and a novel togavirus-like virus, were isolated from ISA disease outbreaks that were first reported as a new syndrome, haemorrhagic kidney syndrome (HKS) affecting farmed Atlantic salmon Salmo salar L. on the East coast of Canada. Laboratory confirmation of ISA diagnosis was initially complicated by isolation of only the togavirus-like agent using the CHSE-214 cell line. Here we demonstrate that a clinical sample from a disease outbreak of ISA contained a mixture of ISA virus and togavirus-like virus. Reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed the presence of both viruses during serial passage of cultures in SHK-1 and CHSE-214 cells. Virus harvested at passage level 3 in both cell lines caused high mortalities and severe gross pathology consistent with ISA virus infection in experimentally inoculated Atlantic salmon parr (approximately 35 g) in freshwater, beginning 12 d post inoculation. ISA virus was detected by virus isolation from kidney and liver tissues of all dead or moribund fish tested. A comparison of virus isolation, 1-step procedure RT-PCR and RNA dot-blot hybridization for detection of ISA virus (ISAV) in fish tissues showed virus isolation to have 100% sensitivity, followed by RT-PCR (66 and 28% sensitivity in kidney and liver, respectively), with RNA dot-blot hybridization as the least sensitive method (20 and 10% sensitivity in kidney and liver, respectively). No togavirus-like virus was detected in these samples by virus isolation. Moreover, another togavirus-like virus isolate grown in CHSE-214 cells in the absence of any other detectable pathogen was non-pathogenic in experimentally inoculated fish. This study confirms that the original ISA outbreaks in New Brunswick, Canada, were caused solely by ISAV. (+info)
UNA virus: first report of human infection in Argentina.
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Una virus (UNAV), Togaviridae family, is widely distributed in South America, where infections have been detected in mosquitoes and vertebrate hosts (humans, birds and horses). We analyzed human sera from Cordoba inhabitants aged 44 to 89 years and using a neutralization test, we found a prevalence of UNAV antibodies of 3.8% (3/79). The low titers detected suggest past infections probably acquired in rural areas of the Province of Cordoba (central Argentina). None sera were found positive for MAYV neutralizing antibodies. This is the first report of human infections by UNAV in Argentina. (+info)
A delayed-type hypersensitivity-inducing T-cell epitope of Semliki Forest virus mediates effective T-helper activity for antibody production.
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The rational development of peptide vaccines requires the identification of both B- and T-cell epitopes. In this study, potential T-helper cell epitopes of Semliki Forest virus (SFV) were identified on the basis of their ability to induce delayed-type hypersensitivity (DTH) in mice using recombinant SFV fragments produced as hybrid proteins with beta-galactosidase in Escherichia coli and synthetic peptides coupled to beta-galactosidase. Although the tested fragments spanned almost the entire amino acid sequence of the structural proteins of SFV, only one DTH-inducing region (located between amino acid 137 and 151 of the SFV E2 membrane protein) was identified. Peptides containing this E2 region stimulated lymph node cells from SFV-primed mice in vitro. The ability of the identified T-cell epitope to induce a specific T-helper response in mice was evaluated using synthetic peptides that contained combinations of the DTH-inducing region and different previously identified linear B-cell epitopes of E2. These peptides proved able to induce an antipeptide IgG response in mice in an H-2d-restricted fashion. One of the peptides was also able to induce high titres of IgG reactive with SFV-infected cells and protected 70-100% of the peptide-immunized mice after challenge with virulent SFV. Our findings suggest that DTH and T-helper activity are mediated by different doses of the same T-cell epitope. (+info)
Misfolding and aggregation of newly synthesized proteins in the endoplasmic reticulum.
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As a part of our studies on the folding of glycoproteins in the ER, we analyzed the fate of viral glycoproteins that have misfolded either spontaneously or through inhibition of N-linked glycosylation. Newly synthesized Semliki Forest virus spike glycoproteins E1 and p62 and influenza hemagglutinin were studied in infected and transfected tissue culture cells. Misfolded proteins aggregated in less than 1 min after release from polysomes and aberrant interchain disulfide bonds were formed immediately. When more than one protein was misfolded, mixed aggregates were generated. This indicated that the formation of complexes was nonspecific, random, and not restricted to products from single polysomes. The size of the aggregates varied from small oligomers to complexes of several million daltons. BiP was associated noncovalently with the aggregates and with some of the nonaggregated products. We conclude that aggregation reflects the poor solubility of incompletely folded polypeptide chains. (+info)