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Influenza A prevalence and subtype diversity in migrating teal sampled along the United States Gulf Coast

March 4, 2019

Wild birds in the order Anseriformes are important reservoirs for influenza A viruses (IAV); however, IAV prevalence and subtype diversity may vary by season, even at the same location. To better understand the ecology of IAV during waterfowl migration through the Gulf Coast of the United States (Louisiana and Texas), surveillance of blue-winged (Spatula discors) and American green-winged (Anas carolinensis) teal was conducted annually during the spring (live-capture; 2012-2017) and fall (hunter-harvested; 2007-2017) at times inferred to coincide with northward and southward movements, respectively, for these waterfowl species. During spring migration, 266 low pathogenicity (LP) IAV positive samples were recovered from 7,547 paired cloacal/oropharyngeal (COP) samples (prevalence: 3.5%; annual range: 1.3%-8.4%). During fall migration, 650 LP IAV positive samples were recovered from 9,493 COP samples (prevalence: 6.8%; annual range: 0.4%-23.5%). Overall, 34 and 20 different IAV subtypes were recovered during fall and spring sampling, respectively. Consistent with previous results for fall migrating ducks, H3 and H4 HA subtypes were most common; however, H4 subtype viruses predominated every year. This is in contrast to the predominance of LP H7 and H10 HA subtype viruses in both species during spring. The N6 and N8 NA subtypes, which were usually associated with H4, were most common during fall; the N6 subtype was not recovered in the spring. These consistent seasonal trends in IAV subtype detection in both species are currently not understood and highlight the need for further research regarding potential drivers of spatiotemporal patterns of infection such as population immunity.

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