Characterization of a genetic and antigenic variant of avian paramyxovirus 6 isolated from a migratory wild bird, the red-necked stint (Calidris ruficollis).

A hemagglutinating virus (8KS0813) was isolated from a red-necked stint. Hemagglutination inhibition and neutralization tests indicated that 8KS0813 was antigenically related to a prototype strain, APMV-6/duck/Hong Kong/18/199/77, but with an 8- and 16-fold difference, respectively, in their titers. The full genome sequence of 8KS0813 showed 98.6 % nucleotide sequence identity to that of APMV-6/duck/Italy/4524-2/07, which has been reported to belong to an APMV-6 subgroup, and showed less similarity to that of the prototype strain (70.6 % similarity). The growth of 8KS0813 and the prototype strain in four different cell cultures was greatly enhanced by adding trypsin. Interestingly, this virus induced syncytia only in Vero cells. 8KS0813 was identified as APMV-6/red-necked stint/Japan/8KS0813/08, but it is antigenically and genetically distinguishable from the prototype strain, suggesting that variant APMV-6 is circulating in migratory birds.

H4N8 subtype avian influenza virus isolated from shorebirds contains a unique PB1 gene and causes severe respiratory disease in mice.

H4N8 subtype avian influenza viruses were isolated from shorebirds in eastern Hokkaido. All the isolates shared >99.7% nucleotide homology, and all the viral genes except for PB1 were highly related to those of A/red-necked stint/Australia/1/04. Thus, the isolates were regarded as PB1 reassortants. The most similar PB1 gene was identified in A/mallard/New Zealand/1615-17/04 (H4N6) with nucleotide homology of 90.9%. BALB/c mice intranasally inoculated with the H4N8 isolates developed severe respiratory disease, which eventually led to death in some mice. The virus was isolated from the lungs, and viral antigen was detected in the lungs with pneumonia. Other H4 subtype viruses tested did not cause any symptoms in mice, although these viruses were also isolated from the lungs. The PB2 gene of the H4N8 isolates contains K482R, but not the E627K or D701N substitutions. The PB1-F2 gene of the isolates consists of a 101-amino acid unique sequence, but lacks the N66S mutation.

Surveillance of avian influenza virus in migratory water birds in eastern Hokkaido, Japan.

The epidemiological information has obtained on avian influenza virus (AIV) in eastern Hokkaido, Japan, where AIV surveillance has not been performed. Cloacal or fecal samples obtained from migratory water birds were screened for AIV both by real-time reverse transcriptase polymerase chain reaction to detect the influenza A virus matrix (M) gene and by egg inoculation. Between 2007 and 2009, a total of 2,488 samples were collected from various avian species in Abashiri, Kushiro, Nemuro and Tokachi districts of eastern Hokkaido. AIVs were isolated from 18 of those samples (0.7%). No AIV was isolated from the 1,449 samples collected in Abashiri, Kushiro and Nemuro districts, although 6 were positive for the M gene by RRT-PCR. In contrast, 52 (5.0%) of the 1,039 samples collected from ducks in Tokachi district were M gene positive; AIVs were isolated from 18 of those samples (1.7%). The isolates included H3N5 (1 isolate), H3N6 (1), H3N8 (9), H4N2 (1), H4N6 (2), H6N5 (1), H6N8 (1), and H11N3 (2) subtypes. H3N5 and H11N3 subtypes have not been frequently isolated, and our study is the first to report H3N5 and the second to report H11N3 in Japan. Phylogenetic analysis revealed that the M genes of all isolates belonged to the Eurasian lineage.