Analytical validation of a real-time reverse transcription polymerase chain reaction test for Pan-American lineage H7 subtype Avian influenza viruses.
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A real-time reverse transcription polymerase chain reaction test for the identification of the H7 subtype in North American avian influenza viruses AIV was first reported in 2002; however, recent (AIVs) surveillance efforts in wild birds and H7 outbreaks in poultry demonstrated that the 2002 test did not detect all H7 AIVs present in North and South America. Therefore, a new test, the 2008 Pan-American H7 test, was developed by using recently available H7 nucleotide sequences. The analytical specificity of the new assay was characterized with an RNA panel composed of 19 H7 viruses from around the world and RNA from all hemagglutinin subtypes except H16. Specificity for North and South American lineage H7 viruses was observed. Assay limits of detection were determined to be between 10(3) and 10(4) gene copies per reaction with in vitro transcribed RNA, and 10(0.0) and 10(0.8) 50% egg infectious doses per reaction. The 2008 Pan-American H7 test also was shown to perform similarly to the 2002 test with specimens from chickens experimentally exposed to A/Chicken/BritishColumbia/314514-2/04 H7N3 highly pathogenic AIV. Furthermore, the 2008 test was able to detect 100% (n = 27) of the H7 AI, V isolates recovered from North American wild birds in a 2006-2007 sample set, (none of which were detected by the 2002 H7 test). (+info)
Compatibility among polymerase subunit proteins is a restricting factor in reassortment between equine H7N7 and human H3N2 influenza viruses.
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Genetic Analyses of an H3N8 Influenza Virus Isolate, Causative Strain of the Outbreak of Equine Influenza at the Kanazawa Racecourse in Japan in 2007.
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In August 2007, an outbreak of equine influenza occurred among vaccinated racehorses with Japanese commercial equine influenza vaccine at Kanazawa Racecourse in Ishikawa prefecture in Japan. Apparent symptoms were pyrexia (38.2-41.0 degrees C) and nasal discharge with or without coughing, although approximately half of the infected horses were subclinical. All horses had been shot with a vaccine that contained two inactivated H3N8 influenza virus strains [A/equine/La Plata/93 (La Plata/93) of American lineage and A/equine/Avesta/93 (Avesta/93) of European lineage] and an H7N7 strain (A/equine/Newmarket/1/77). Influenza virus, A/equine/Kanazawa/1/2007 (H3N8) (Kanazawa/07), was isolated from one of the nasal swab samples of diseased horses. Phylogenetic analysis indicated that Kanazawa/07 was classified into the American sublineage Florida. In addition, four amino acid substitutions were found in the antigenic sites B and E in the HA1 subunit protein of Kanazawa/07 in comparison with that of La Plata/93. Hemagglutination-inhibition (HI) test using 16 serum samples from recovering horses revealed that 1.4- to 8-fold difference in titers between Kanazawa/07 and either of the vaccine strains. The present findings suggest that Japanese commercial inactivated vaccine contributed to reducing the morbidity rate and manifestation of the clinical signs of horses infected with Kanazawa/07 that may be antigenically different from the vaccine strains. (+info)
Homologous recombination as an evolutionary force in the avian influenza A virus.
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Acquisition of a polybasic hemagglutinin cleavage site by a low-pathogenic avian influenza virus is not sufficient for immediate transformation into a highly pathogenic strain.
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Pathology and virus distribution in chickens naturally infected with highly pathogenic avian influenza A virus (H7N7) During the 2003 outbreak in The Netherlands.
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