Characterization of low pathogenicity avian influenza viruses isolated from wild birds in Mongolia from 2009 to 2018

Abstract

Background: Since 2005, highly pathogenic avian influenza A H5N1 viruses (Goose/Guangdong/1/96-H5 lineage) have spread from Asia to Africa and Europe, infecting poultry, humans and wild birds. Subsequently, avian influenza surveillance has increased worldwide. Mongolia is a good location to study influenza viruses in wild birds within Asia because the country has very low densities of domestic poultry and supports large concentrations of migratory water birds. We conducted avian influenza surveillance in Mongolia over two time periods from 2009 to 2018, utilizing environmental fecal sampling.Methods: Fresh fecal samples were collected in areas where wild water birds, including orders Anseriformes and Charadriiformes, congregated. Hemagglutinin (HA) and neuraminidase (NA) subtypes of positive samples were identified through viral isolation or molecular assays, with pathogenicity determined by HA subtype or sequencing the HA cleavage site.Results: A total of 10,222 samples were collected and tested for avian influenza virus. Of these, 7,025 fecal samples were collected from 2009-2013, and 3,197 fecal samples were collected from 2016-2018 period. Testing revealed 175 (1.7%) positive samples for low pathogenicity influenza A, including 118 samples from 2009-2013 (1.7%) and 57 samples from 2016-2018 (1.8%). Over the period and locations of surveillance no influenza A viruses were detected in association with a wild bird mortality event. HA and NA subtyping of all positives identified eleven subtypes of HA (H1-H8; H10-H12) and nine subtypes of NA (N1-N9) in 29 different combinations. Within periods, viruses were detected more frequently during the fall season (August to October, 2.5%; 95% CI 2.1-2.9%; 146/5,750) than the early summer (April to July, 0.6%; 95% CI 0.4-0.9%; 29/4,472).Conclusion: Mongolia is an important location for wild birds and is positioned as a crossroad of multiple migratory bird flyways. Breeding birds from Mongolia and further north pass through the country to wintering areas as widespread as southern Africa, the Indian Subcontinent, Southeast Asia and Australasia. Our work demonstrates the feasibility of using an affordable environmental fecal sampling approach for avian influenza surveillance and contributes to understanding the prevalence and ecology of low pathogenicity avian influenza viruses in this important location, where birds from multiple flyways mix.