Abstract:
Influenza A viruses cause influenza in multiple species of avian and mammals, including human being. Due to the frequently movement and sharing the same habitat with wild birds and other backyard poultry, free-grazing ducks in Thailand have potential to spread influenza A viruses. In this study, a 4-months longitudinal survey of influenza A viruses was conducted in two of free-grazing duck flocks (flock A and B) raised in Phichit and Phitsanulok. Two subtypes of influenza A viruses, H4N6 (n=1) and H3N8 (n=5), were isolated from flock B at the age of 13 and 15 weeks, respectively. It noted that both virus subtypes were collected from the different location. The signs of depression and ocular discharge were observed in the virus isolated ducks. Phylogenetic analysis and genetic characterization indicated that all virus isolates were clustered in the Eurasian lineage and indicated as low pathogenic avian influenza viruses. It noted that no virus was isolated from flock A. Serological analysis showed that the seropositive ducks were detected at 9 and 13 weeks old in flock A and B, respectively. Interestingly, all virus isolated ducks were seropositive for ELISA, but none was positive in the HI test with homologous viruses. In summary, our results indicated that free-grazing ducks have potential to be the reservoir and transmitting influenza A viruses. The continued survey of influenza A virus in free-grazing ducks can be benefit for the prevention and control strategy of the next influenza outbreak.
