Genetic characterization of influenza a viruses recovered from wild birds and quails in Thailand

Abstract

This dissertation contains 3 parts of study. Part 1, a 15-month monitoring program of influenza A virus (IAVs) was conducted in wild birds in central Thailand; Ayutthaya and Suphanburi from February 2009 to April 2010. The result showed that the occurrence of IAVs in wild birds was 2.07% (62/2,994). Four IAVs subtype H12N1 were isolated from watercock (n=1) and lesser whistling-duck (n=3). Interestingly, this study is the first to report the circulation of IAV subtype H12N1 in Thailand and to describe the genetic characteristics of H12N1 in Eurasia. Part 2, a 12-month monitoring program of IAVs in quails was conducted in two quail farms in Ayutthaya and Suphanburi from May 2009 to April 2010. The result showed that the occurrence of IAVs in quails was 1.18% (24/2,040). Three IAVs subtype H7N1 were isolated from a quail farm in Ayutthaya. It should be noted that IAV subtype H7N1 had never been reported in the country. Genetic characteristics of one H7N1 virus revealed that the virus was classified to be low pathogenic, however neuraminidase (NA) gene was closely related to highly pathogenic avian influenza subtype H5N1 (HPAI-H5N1) in Eurasian lineage of Vietnam and Thailand. Part 3, DNA aptamers against swine influenza virus (SIV) H3N2 were developed through systematic evolution of ligands by exponential enrichment (SELEX). Four candidate aptamers (HA68, HA7, HA2a and HA2b) were identified and characterized. The results showed that DNA aptamers from this study can be used to detect and differentiate influenza subtypes. In conclusion, this dissertation reported the novel subtypes of IAVs circulating in Thailand; H12N1 in wild bird species and H7N1 in quails. Monitoring and genetic characterization of IAVs in wild bird and quail populations should be continuously conducted to promote an awareness of IAVs infection in animals and humans in the future. Subtype specific aptamers against SIVs developed from this study can also be used in rapid detection and typing protocols for field applications.