Disease Survey and Health Assessment of Free-Ranging British Columbia Sea Otters (Enhydra lutris)
Sea otters (Enhydra lutris) play an important role in structuring the kelp ecosystem in temperate coastal regions of the North Pacific Ocean by shaping the abundance, diversity and dispersal of those invertebrate grazers that control kelp growth.7 Sea otters serve as indicators of the overall health of the coastal marine ecosystem.
Current estimates put the North Pacific sea otter population at less than 100,000. As a consequence of the heavy demand for sea otter pelts in the 19th and early 20th centuries, the Canadian population of sea otters was extirpated by 1929. Translocation efforts were carried out between 1969 and 19721-5, which resulted in a current population of approximately 3,100 animals.6 Sea otters in Canada are protected under the Species at Risk Act (SARA) and currently listed as threatened under schedule I, by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC).
Because of their threatened status, baseline information is needed on the health of individuals and the threats facing the population. Living in a relatively pristine environment away from major human activity, we hypothesized that the BC sea otters would have little evidence of disease from the hematologic and serum biochemical values and little to no evidence of pathogen exposure and antimicrobial resistance. We conducted an evaluation of hematology and serum chemistry, pathogen exposure and antimicrobial resistance in 42 free-ranging BC sea otters that were live-captured in September of 2003 and 2004. The sea otters were captured under the terms of scientific and animal care permits issued by the Canadian Department of Fisheries and Oceans.
Hematological data generally fell within reference ranges from other studies. High levels of creatinine phosphokinase and aspartate aminotransferase were detected and may have been the result of transient muscle damage during the capture and handling of these animals. There were differences noted in the alkaline phosphatase and the phosphorus between adults and pups/juveniles, consistent with age-related changes seen in other species. We found no evidence of exposure in sea otters to Brucella, herpes virus nor West Nile Virus, the latter of which has not yet been detected in British Columbia. All of the otters had negative titers (IFAT) to Sarcocystis neurona and Neospora caninum, while two of the otters (2004) had IFAT titers suggesting exposure to Toxoplasma gondii. Eight of the 24 otters (2004) tested positive for canine distemper virus using virus neutralization assays. Exposure to Toxoplasma gondii and morbillivirus has significant implications regarding potential sources of exposure. Fecal isolates of Escherichia coli did not demonstrate detectable patterns of antimicrobial resistance.
This study provides baseline data for free-ranging BC sea otters, which should prove useful as a tool for; rehabilitation and treatment in captive facilities, determining the potential impact of diseases and providing a foundation for long-term monitoring of the population.
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