Search

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.

The southern sea otter (Enhydra lutris nereis) is a threatened marine sentinel. During postmortem investigations of stranded sea otters from 2004 to 2013 in California, US, papillomas were detected in the oral cavity of at least seven otters via necropsy and histopathology. Next-generation sequencing of viral particles purified from a single papilloma revealed a novel papillomavirus, Enhydra lutris papillomavirus 1 (ElPV-1). The genome of ElPV-1 was obtained, representing the first fully sequenced viral genome from southern sea otters. Phylogenetic analysis of the entire L1 gene, as well as a concatenated protein identities plot of all papillomaviral genes revealed that ElPV-1 is a λ-papillomavirus, related to a raccoon papillomavirus (Procyon lotor papillomavirus type 1) and a canine oral papillomavirus. Immunohistochemical staining, using a cross-reactive bovine papillomavirus antibody, suggested that ElPV-1 is present in intranuclear inclusions and intracytoplasmic keratin granules. Virus-infected cells were scattered throughout the stratum granulosum and stratum spinosum of the gingival and buccal papillomas. Using ElPV-1-specific PCR, we confirmed viral DNA in oral papillomas from all seven stranded sea otters, with identical L1 sequences. This virus is associated with the development of oral papillomatosis in southern sea otters.