Abstract

Influenza A virus (IAV) has been associated with multiple unusual mortality events (UMEs) in North Atlantic pinnipeds, frequently attributed to spillover of virus from wild bird reservoirs. To determine if endemic infection persists outside of UMEs, we undertook a multiyear investigation of IAV in healthy, live-captured Northwest Atlantic gray seals (Halichoerus grypus). From 2013–2015, we sampled 345 pups and 57 adults from Cape Cod, MA, United States and Nova Scotia, Canada consistently detecting IAV infection across all groups. There was an overall viral prevalence of 9.0% (95% confidence interval (CI): 6.4–12.5%) in weaned pups and 5.3% (CI: 1.2–14.6%) in adults, with seroprevalences of 19.3% (CI: 15.0–24.5%) and 50% (CI: 33.7–66.4%), respectively. Positive sera showed a broad reactivity to diverse influenza subtypes. IAV status did not correlate with measures of animal health or impact animal movement or foraging. This study demonstrated that Northwest Atlantic gray seals are both permissive to and tolerant of diverse IAV, possibly representing an endemically infected wild reservoir population.

Acknowledgements

This work was supported in part by NIAID CEIRS HHSN272201400008C, NMFS #17670-01, and FWS #3-1383-R. We thank Hon Ip for graciously providing the IAV isolate A/harbor seal/New Hampshire/179629/2011/H3N8, and the influenza research database for providing reference sera. We are grateful to Holly Bayley and the National Park Service for boat support, Monomoy National Wildlife Refuge for use of the Monomoy lighthouse, Terri Rowles and the NOAA Marine Mammal Health and Stranding Response Program for field supplies, Crocker Snow for use of his cabin and access to private lands on Muskeget Island, Sarah Oktay for assistance with the University of Massachusetts field station on Nantucket, and Kathryn Ono for facilitating initial work on Muskeget Island. This work is not possible without numerous dedicated and skilled volunteers from the University of New England, University of Rhode Island, Riverhead Foundation for Marine Research and Preservation, Marine Mammals of Maine, National Marine Life Center, International Fund for Animal Welfare, New England Aquarium, Mystic Aquarium, Northeast Fisheries and Science Center Woods Hole, North Atlantic Seal Research Consortium, and Woods Hole Oceanographic Institution.

* Presenting author