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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.

The 2016–2017 introduction of peste des petits ruminants virus (PPRV) into livestock in Mongolia was followed by mass mortality of the critically endangered Mongolian saiga antelope and other rare wild ungulates. To assess the nature and population effects of this outbreak among wild ungulates, we collected clinical, histopathologic, epidemiologic, and ecological evidence. Molecular characterization confirmed that the causative agent was PPRV lineage IV. The spatiotemporal patterns of cases among wildlife were similar to those among livestock affected by the PPRV outbreak, suggesting spillover of virus from livestock at multiple locations and time points and subsequent spread among wild ungulates. Estimates of saiga abundance suggested a population decline of 80%, raising substantial concerns for the species’ survival. Consideration of the entire ungulate community (wild and domestic) is essential for elucidating the epidemiology of PPRV in Mongolia, addressing the threats to wild ungulate conservation, and achieving global PPRV eradication.

Classical swine fever (CSF), a highly contagious viral disease affecting domestic and wild pigs in many developing countries, is now considered endemic in Mongolia, with 14 recent outbreaks in 2007, 2008, 2011, 2012, 2014, and 2015. For the first time, CSF viruses isolated from these 14 outbreaks were analyzed to assess their molecular epidemiology and pathogenicity in pigs. Based on the nucleotide sequences of their 5'-untranslated region, isolates were phylogenetically classified as either sub-genotypes 2.1b or 2.2, and the 2014 and 2015 isolates, which were classified as 2.1b, were closely related to isolates from China and Korea. In addition, at least three different viruses classified as 2.1b circulated in Mongolia. Experimental infection of the representative isolate in 2014 demonstrated moderate pathogenicity in 4-week-old pigs, with relatively mild clinical signs. Understanding the diversity of circulating CSF viruses gleans insight into disease dynamics and evolution, and may inform the design of effective CSF control strategies in Mongolia.

Migratory water birds are the natural reservoir of influenza A viruses. H5 and H7 influenza viruses are isolated over the world and also circulate among poultry in Asia. In 2010, two H5N1 highly pathogenic avian influenza viruses (HPAIVs) were isolated from fecal samples of water birds on the flyway of migration from Siberia, Russia to the south in Hokkaido, Japan. H7N9 viruses are sporadically isolated from humans and circulate in poultry in China. To monitor whether these viruses have spread in the wild bird population, we conducted virological surveillance of avian influenza in migratory water birds in autumn from 2010 to 2014. A total of 8103 fecal samples from migratory water birds were collected in Japan and Mongolia, and 350 influenza viruses including 13 H5 and 19 H7 influenza viruses were isolated. A phylogenetic analysis revealed that all isolates are genetically closely related to viruses circulating among wild water birds. The results of the antigenic analysis indicated that the antigenicity of viruses in wild water birds is highly stable despite their nucleotide sequence diversity but is distinct from that of HPAIVs recently isolated in Asia. The present results suggest that HPAIVs and Chinese H7N9 viruses were not predominantly circulating in migratory water birds; however, continued monitoring of H5 and H7 influenza viruses both in domestic and wild birds is recommended for the control of avian influenza.

Between August and September 2016 pathological samples were collected from sheep and goats following suspected peste des petits ruminants (PPR) outbreaks in western Mongolia. RT-PCR followed by sequencing and phylogenetic analysis of the samples confirmed the presence of a PPR virus belonging to lineage IV. A full genome analysis of the viral RNA from one of the samples revealed a high similarity (99.0-99.5%) with PPR viruses currently circulating in China (2013-2015) indicating a common origin. This is the first genetic characterization of PPR virus in Mongolia and the data generated will have important implications for control and management of the disease in the region.