Canine distemper virus in the Washington State sea otter population

Authors: THOMAS, NANCY - Us Geological Survey (USGS); WHITE, LEANN - Us Geological Survey (USGS); SALIKI, JEREMIAH - University Of Georgia; SCHULER, KRYSTEN - Cornell University; LYNCH, DEANNA - Department Of Fish And Wildlife; NIELSEN, OLE - Department Of Fisheries And Oceans Canada; Dubey, Jitender; KNOWLES, SUSAN - Us Geological Survey (USGS)

Submitted to: Journal of Wildlife Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2020
Publication Date: 10/1/2020
Citation: Thomas, N., White, L.C., Saliki, J., Schuler, K., Lynch, D., Nielsen, O., Dubey, J.P., Knowles, S. 2020. Canine distemper virus in the Washington State sea otter population. Journal of Wildlife Diseases. 56(4):873-883. https://doi.org/10.7589/JWD-D-19-00008.
DOI: https://doi.org/10.7589/JWD-D-19-00008

Interpretive Summary: Coccidia are a group of single celled parasites. This group of protozoa include important genera: Eimeria, Cystoisospora, Cyclospora, Sarcocystis, Toxoplasma, Isospora that can cause serious illness in livestock, poultry, and humans and some species are zoonotic (parasites transmitted from animals to humans). The disease can be serious in animals and humans co-infected with immunosuppressive agents such as Human Immunodeficiency Virus (HIV). Morbillivirus is an immunosppressive virus related to HIV. Sarcocystosis is a common cause of mortality in sea otters and several other species of marine mammals in USA. Most serious cases of toxoplasmosis and sarcocystosis in sea otters were associated with the morbillivirus infection. Here, the authors discuss the role of morvillivirus and protozoan infections in marine mammals. This information will be of interests to wildlife biologists, parasitologists and veterinarians.

Technical Abstract: Morbillivirus epidemics in marine mammals first gained prominence in 1988 when an outbreak of phocine distemper virus occurred in European harbor seals (Phoca vitulina vitulina). Prior to 2001, all serosurveys for morbilliviruses in sea otters (Enhydra lutris) in California, Washington and Alaska documented a 0% seroprevalence. The first published serodetections of morbillivirus in sea otters occurred in 2001–2002 in live-captured Washington sea otters with a documented 80% seroprevalence. We conducted a retrospective study of sea otter cases from 1989–2010 compiled at the U.S. Geological Survey’s National Wildlife Health Center to identify cases of morbilliviral disease in Washington sea otters, and to further characterize the disease using immunohistochemistry, RT-PCR, genetic sequencing and virus isolation. We identified six cases of morbilliviral disease and 12 of morbilliviral infection in this population of sea otters during 2000–2010. Significant histologic findings included inflammation in the white and gray matter of the brain characterized by lymphoplasmacytic perivascular cuffing, neuronal necrosis and satellitosis in gray matter and spongiosis, myelin degeneration, spheroids, and gemistocytes in white matter. Intranuclear and intracytoplasmic viral inclusion bodies were found in neurons, Purkinje cells and glia. Immunohistochemistry for canine distemper virus showed positive staining in neurons, glial cells and cell processes. A pan-morbillivirus RT-PCR with subsequent restriction endonuclease digestion or sequencing identified canine distemper virus. Virus isolation was not successful. Histologic changes were confined to the central nervous system and resembled neurologic canine distemper virus in domestic dogs. Cases of otters with morbilliviral infection without histologic changes could represent early infections or incompletely cleared sublethal infections. Our findings indicate that morbillivirus was present in the Washington sea otter population as early as 2000 and provides a description of the pathology of canine distemper virus in sea otters.