Small Variations Between Species/Subtypes Attributed to Reassortment Evidenced from Polymerase Basic Protein 1 with Other Seven Proteins from Influenza A Virus

This is a continuation of our studies previously published in this journal to use data analysis to explore why the reassortment of genetic segments from different host species and from different subtypes of influenza A viruses occurred frequently, which was considered the main reason for the generation of new strains. Of eleven proteins from influenza A virus, we have studied seven proteins in our previous studies. To get a full picture, 2352 polymerase basic proteins 1 from influenza A viruses were analysed. The results showed that the variations between host species/subtypes are smaller than those within host species/subtype. In combination with the results obtained from hemagglutinin, neuraminidase, nucleoprotein, matrix proteins 1 and 2, polymerase acidic protein and polymerase basic proteins 1 and 2, the results suggested that the predisposition to reassortment of genetic segments of influenza A virus from different host species and subtypes was mainly because of the small variations between the virus isolates.     

Molecular and Antigenic Characterization of Triple‐Reassortant H3N2 Swine Influenza Viruses Isolated from Pigs,Turkey and Quail in Canada

In 2005, triple‐reassortant H3N2 (trH3N2) influenza A viruses were isolated from swine and turkeys in Canada. Subsequently, these viruses were isolated from humans and mink in 2006 and 2007, respectively. Following full genome sequencing, H3N2 viruses isolated from turkeys (2005), quail (2008) and swine (2009) in Canada, were characterized as trH3N2. The 2005 turkey isolate was found to be almost identical to other viruses isolated in that year, with quail and pig isolates related very closely to the 2005 trH3N2. Minimal antigenic evolution of the swine isolates relative to the reference 2005 virus was observed. These results suggest the establishment of a stable lineage of trH3N2 in Canadian pigs, with evidence for interspecies transmission to turkeys and quails.     

Surveillance and investigative diagnosis of a poultry flock in Great Britain co‐infected with an influenza A virus and an avirulent avian avulavirus type 1

A detailed veterinary and laboratory investigation revealed an unusual case of concurrent avian avulavirus type 1 (AAvV‐1, formerly called avian paramyxovirus type 1) and low pathogenicity avian influenza (LPAI) virus infections of chickens during March 2010 in a mixed poultry and livestock farm in Great Britain. Respiratory signs and daily mortality of 5–6 birds in a broiler flock 8‐weeks of age prompted submission of two carcasses to an Animal and Plant Health Agency (APHA) regional laboratory. Infectious bronchitis virus infection was suspected initially and virus isolation in SPF embryonated fowls’ eggs was attempted at APHA‐Weybridge. Avirulent AAvV‐1 was detected in the first sampling. Both in vitro nucleotide sequencing of the fusion gene and in vivo pathotyping by intracerebral pathogenicity index revealed an avirulent AAvV‐1 not definitively ascribed to licensed vaccine. Upon initial detection of the AAvV‐1 virus, statutory restrictions were placed on the farm, an official veterinary visit was performed and further samples were submitted to APHA‐Weybridge for official statutory disease investigation. An H2N3 LPAI virus was subsequently isolated from tissue samples and swabs submitted from the follow‐up statutory investigation. The subtype was confirmed by haemagglutination inhibition test (HAIT) and neuraminidase inhibition (NI) tests on egg‐amplified virus. As neither virus was notifiable according to the internationally recognized EU and OIE standards, and/or definitions of disease, statutory farm restrictions were lifted. Veterinary investigations identified the broiler flock to be free‐range, next to a river and duck pen, reinforcing the suspicion of wild bird origin for both viruses which may have been co‐circulating in ducks. It could not, however, be established as to whether there were separate introductions of the two viruses or whether there had been a single co‐introduction of the viruses. The described case highlights the value of integrated surveillance and laboratory approaches, including veterinary field investigations, international standards and definitions of notifiable avian disease, validated RRT‐PCR assays, and virus isolation in achieving rapid and accurate diagnostic results.