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Low-pathogenic avian influenza viruses in wild migratory waterfowl in a region of high poultry production, Delmarva, Maryland

December 7, 2016

Migratory waterfowl are natural reservoirs for low pathogenic avian influenza viruses (LPAIV) and may contribute to the long-distance dispersal of these diseases as well as spillover into domestic bird populations. Surveillance for AIVs is critical to assessing risks for potential spread of these diseases among wild and domestic bird populations. The Delmarva Peninsula on the east coast of the U.S. is both a key convergence point for migratory Atlantic waterfowl populations and a region with high poultry production (greater than 4,700 poultry meat facilities). Sampling of key migratory waterfowl species occurred at 22 locations in the Maryland portion of the Delmarva Peninsula in fall/winter of 2013-2014. Samples were collected from 400 hunter-harvested or live caught birds via cloacal and oropharyngeal swabs. Fourteen of the 400 (3.5%) birds sampled tested positive for the AIV matrix gene, with all positives isolated from five dabbling duck species. Further characterization of the 14 viral isolates identified two hemagglutinin (H3 and H4) and four neuraminidase (N2, N6, N8, and N9) subtypes, two of which have not previously been reported from the Delmarva (H4, N9). Three of 14 isolates contained multiple HA or NA subtypes. This study provides a baseline for the monitoring of AIVs in migratory waterfowl populations in the Delmarva Peninsula, particularly prior to the highly pathogenic AIV outbreaks A(H5N8) and A(H5N2) introduced to the U.S. in late 2014.