Cocirculation of two distinct lineages of equine influenza virus subtype H3N8.
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Direct amplification and sequencing of the hemagglutinin (HA) genes of equine influenza virus subtype H3N8 was undertaken in order to characterize strains of this virus circulating in Sweden. The majority of viruses from outbreaks during 1997 analyzed belonged to the American lineage of H3 equine influenza, and one strain was shown to belong to the European lineage. Furthermore, it was shown that recent American-lineage strains are mutated at amino acid position 190 of the HA during serial passage in embryonated hens' eggs. Host cell adaptation of these viruses thus takes place at antigenic region B of the HA. (+info)
Isolation, sequencing and phylogenetic analysis of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 and H3N8.
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We report here on the isolation and sequencing of the hemagglutinin, neuraminidase and nucleoprotein genes of the Chilean equine influenza virus subtypes H7N7 (A/equi-1/Santiago/77, Sa77) and H3N8 (A/equi-2/Santiago/85, Sa85). The sequences obtained allowed a variability analysis, which indicated significant differences when compared with other isolates. We found that Chilean isolates are more similar to the North American variety than to European isolates. Isolate Sa77 is a good candidate for inclusion in a vaccine as it is the latest isolate of the subtype H7N7 and is probably better-adapted to the equine host. Isolate Sa85, of subtype H3N8, also appears to be a good candidate since it has no significant differences in the main antigenic sites with recent isolates. (+info)
Transmission of equine influenza virus to dogs.
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Molecular and antigenic analyses of three influenza viruses isolated from outbreaks of severe respiratory disease in racing greyhounds revealed that they are closely related to H3N8 equine influenza virus. Phylogenetic analysis indicated that the canine influenza virus genomes form a monophyletic group, consistent with a single interspecies virus transfer. Molecular changes in the hemagglutinin suggested adaptive evolution in the new host. The etiologic role of this virus in respiratory disease was supported by the temporal association of rising antibody titers with disease and by experimental inoculation studies. The geographic expansion of the infection and its persistence for several years indicate efficient transmission of canine influenza virus among greyhounds. Evidence of infection in pet dogs suggests that this infection may also become enzootic in this population. (+info)
Real-time reverse transcription PCR for detection and quantitative analysis of equine influenza virus.
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Equine influenza is a cause of epizootic respiratory disease of the equine. The detection of equine influenza virus using real-time Light Cycler reverse transcription (RT)-PCR technology was evaluated over two influenza seasons with the analysis of 171 samples submitted for viral respiratory disease. Increased sensitivity was found in overall viral detection with this system compared to Directigen Flu A and virus isolation, which were 40% and 23%, respectively, that of the RT-PCR. The assay was also evaluated as a viable replacement for the more traditional methods of quantifying equine influenza virus, 50% egg infectious dose and 50% tissue culture infectious dose. There was a significant positive correlation (P<0.05) between the quantitative RT-PCR and both of these assays. (+info)
Screening of feral pigeon (Colomba livia), mallard (Anas platyrhynchos) and graylag goose (Anser anser) populations for Campylobacter spp., Salmonella spp., avian influenza virus and avian paramyxovirus.
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A total of 119 fresh faecal samples were collected from graylag geese migrating northwards in April. Also, cloacal swabs were taken from 100 carcasses of graylag geese shot during the hunting season in August. In addition, samples were taken from 200 feral pigeons and five mallards. The cultivation of bacteria detected Campylobacter jejuni jejuni in six of the pigeons, and in one of the mallards. Salmonella diarizona 14: k: z53 was detected in one graylag goose, while all pigeons and mallards were negative for salmonellae. No avian paramyxovirus was found in any of the samples tested. One mallard, from an Oslo river, was influenza A virus positive, confirmed by RT-PCR and by inoculation of embryonated eggs. The isolate termed A/Duck/Norway/ 1/03 was found to be of H3N8 type based on sequence analyses of the hemagglutinin and neuraminidase segments, and serological tests. This is the first time an avian influenza virus has been isolated in Norway. The study demonstrates that the wild bird species examined may constitute a reservoir for important bird pathogens and zoonotic agents in Norway. (+info)
Large-scale sequence analysis of avian influenza isolates.
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The spread of H5N1 avian influenza viruses (AIVs) from China to Europe has raised global concern about their potential to infect humans and cause a pandemic. In spite of their substantial threat to human health, remarkably little AIV whole-genome information is available. We report here a preliminary analysis of the first large-scale sequencing of AIVs, including 2196 AIV genes and 169 complete genomes. We combine this new information with public AIV data to identify new gene alleles, persistent genotypes, compensatory mutations, and a potential virulence determinant. (+info)
Insights into the interaction between influenza virus and pneumococcus.
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Bacterial infections following influenza are an important cause of morbidity and mortality worldwide. Based on the historical importance of pneumonia as a cause of death during pandemic influenza, the increasingly likely possibility that highly pathogenic avian influenza viruses will trigger the next worldwide pandemic underscores the need to understand the multiple mechanisms underlying the interaction between influenza virus and bacterial pathogens such as Streptococcus pneumoniae. There is ample evidence to support the historical view that influenza virus alters the lungs in a way that predisposes to adherence, invasion, and induction of disease by pneumococcus. Access to receptors is a key factor and may be facilitated by the virus through epithelial damage, by exposure or up-regulation of receptors, or by provoking the epithelial regeneration response to cytotoxic damage. More recent data indicate that alteration of the immune response by diminishing the ability of the host to clear pneumococcus or by amplification of the inflammatory cascade is another key factor. Identification and exploration of the underlying mechanisms responsible for this synergism will provide targets for prevention and treatment using drugs and vaccines. (+info)
Efficacy of oseltamivir phosphate to horses inoculated with equine influenza A virus.
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We investigated the efficacy of the oral administration of oseltamivir phosphate (OP) in horses experimentally infected with equine influenza A virus (H3N8). Nine horses were divided into three horses each of control, treatment and prophylaxis groups. An administration protocol for the treatment group (2 mg/kg of body weight, twice a day for five days) was started immediately after the onset of pyrexia (above 38.9 degrees C). An administration protocol for the prophylaxis group (2 mg/kg of body weight, once a day for five days) was started on a day before viral inoculation. In the treatment group, periods of virus excretion (mean days +/- standard deviation, 2.3 +/- 0.6) and pyrexia (2.0 +/- 0.0) were apparently shorter than those of the control group (6.0 +/- 0.0 and 8.0 +/- 1.0, respectively). In the prophylaxis group, although virus excretion and pyrexia were not prevented, the periods of virus excretion (5.0 +/- 0.0) and pyrexia (4.7 +/- 1.5) were shorter than those of the control group. Moreover, in the treatment and prophylaxis groups, bacterial counts of Streptococcus equi subsp. zooepidemicus known as the common pathogen of secondary bacterial pneumonia in bronchoalveolar lavage fluids collected seven days after inoculation were significantly fewer than that of the control group. The results indicated that the oral administration of OP to horses affected with equine influenza would contribute to reduce the magnitude of virus excretion, pyrexia and consequent secondary bacterial pneumonia. (+info)