Serologic Detection of Subtype-specific Antibodies to Influenza A Viruses in Southern Sea Otters (Enhydra lutris nereis)

Abstract

There are approximately 3,000 southern sea otters (Enhydra lutris nereis) in the nearshore environment along the California coast, US, and the species is classified as Threatened under the Endangered Species Act. We tested sera from 661 necropsied southern sea otters sampled from 1997 to 2015 to determine overall exposure to influenza A viruses (IAVs) and to identify subtype-specific antibody responses. Using an enzyme-linked immunosorbent assay (ELISA), antibodies to IAV nucleoproteins were detected in 160 (24.2%) otters, with seropositive animals found in every year except 2008. When the ELISA-positive samples were tested by virus microneutralization, antibody responses were detected to avian-origin hemagglutinin subtypes H1, H3, H4, H5, H6, H7, H9, and H11. Strong antibody responses to pandemic H1N1 (pdmH1N1) were also detected, indicating that epizootic transmission of pdmH1N1 occurred among the southern sea otter population after the emergence of this human-origin virus in 2009. We conclude that southern sea otters are susceptible to infection with avian and human-origin IAV and that exposure to a wide array of subtypes likely occurs during a given otter's 10- to 15-yr life span. Important unanswered questions include what effect, if any, IAV infection has on sea otter health, and how these animals become infected in their nearshore environment.

A Global Perspective on H9N2 Avian Influenza Virus

“…Furthermore, several serosurveys have been performed on mink to look for the prevalence of anti-H9N2 antibodies, all three studies have shown a high seropositivity in farmed minks in China of between 20% and 45% [192,196,197]. Sea otters are also members of the family Mustelidae, a single serosurvey has found antibodies against H9 HA, however, this is perhaps unsurprising considering the presence of H9 viruses in seabirds and the relatively long lifespans of the otters [198].…”

A Global Perspective on H9N2 Avian Influenza Virus

“…Furthermore, several serosurveys have been performed on mink to look for the prevalence of anti-H9N2 antibodies, all three studies have shown a high seropositivity in farmed minks in China of between 20% and 45% [167,171,172]. Sea otters are also members of the family Mustelidae, a single serosurvey has found antibodies against H9 HA, however this is perhaps unsurprising considering the presence of H9 viruses in seabirds and the relatively long lifespans of the otters [173].…”

H9 Influenza Viruses: An Emerging Challenge

“…BJ94like H9N2 viruses have been reported from minks in China, some of which carry the E627K mutation in PB2 associated with mammalian adaptation (Subbarao et al 1993;Hatta et al 2001;Peng et al 2015). Serological studies in sea otters (also in the Mustelidae family) revealed antibodies to H9 viruses, perhaps resulting from exposure to H9 IAVs carried by sea birds (Capuano et al 2017).…”