Clinical Pathology and Assessment of Pathogen Exposure in Southern and Alaskan Sea Otters

Abstract

The southern sea otter (Enhydra lutris nereis) population in California (USA) and the Alaskan sea otter (E. lutris kenyoni) population in the Aleutian Islands (USA) chain have recently declined. In order to evaluate disease as a contributing factor to the declines, health assessments of these two sea otter populations were conducted by evaluating hematologic and/or serum biochemical values and exposure to six marine and terrestrial pathogens using blood collected during ongoing studies from 1995 through 2000. Samples from 72 free-ranging Alaskan, 78 free-ranging southern, and (for pathogen exposure only) 41 debilitated southern sea otters in rehabilitation facilities were evaluated and compared to investigate regional differences. Serum chemistry and hematology values did not indicate a specific disease process as a cause for the declines. Statistically significant differences were found between free-ranging adult southern and Alaskan population mean serum levels of creatinine kinase, alkaline phosphatase, alanine aminotransferase, aspartate aminotransferase, calcium, cholesterol, creatinine, glucose, phosphorous, total bilirubin, blood urea nitrogen, and sodium. These were likely due to varying parasite loads, contaminant exposures, and physiologic or nutrition statuses. No free-ranging sea otters had signs of disease at capture, and prevalences of exposure to calicivirus, Brucella spp., and Leptospira spp. were low. The high prevalence (35%) of antibodies to Toxoplasma gondii in free-ranging southern sea otters, lack of antibodies to this parasite in Alaskan sea otters, and the pathogen's propensity to cause mortality in southern sea otters suggests that this parasite may be important to sea otter population dynamics in California but not in Alaska. The evidence for exposure to pathogens of public health importance (e.g., Leptospira spp., T. gondii) in the southern sea otter population, and the naïveté of both populations to other pathogens (e.g., morbillivirus and Coccidiodes immitis) may have important implications for their management and recovery.

Assessment of Clinical Pathology and Pathogen Exposure in Sea Otters (Enhydra Lutris) Bordering the Threatened Population in Alaska

“…The negative results for San Miguel sea lion virus were consistent with findings by Hanni et al (2003). Although caliciviruses are common marine mammal pathogens and evidence of exposure has been reported in Steller sea lions (Eumetopias jubatus) in the region (Burek et al, 2005), this pathogen does not appear to be of concern in these sea otters.…”

“…Although variations in some parameters were found, the means did not fall outside published ranges for sea otters (Bossart et al, 2001;Hanni et al, 2003), and the differences were not significant physiologically. However, a few individuals had increased values for a small number of analytes compared with published values.…”

“…Because age-related differences in condition and clinical pathology values have been noted among sea otters (Hanni et al, 2003) and were confirmed in this study, comparisons are not presented between age classes and regions but, instead, within each age class for the two regions. The mean, standard deviation, and range for each hematologic and serum chemistry value were calculated for each age class for both study regions.…”

“…Health assessments in Prince William Sound from 1992 to 1993 were follow-up to the Exxon Valdez oil spill in 1989 (Ballachey et al, 2003). A survey was also performed to compare health and pathogen exposure in the southern sea otters off California, USA, to northern sea otters captured in the western Aleutians and southeast Alaska, USA, in 1997 (Hanni et al, 2003). Neither of the previous studies identified biologically significant differences in clinical pathology values associated with specific disease processes or decreased survival.…”

Leptospirosis in Free-Ranging Endangered European Mink (Mustela Lutreola) and Other Small Carnivores (Mustelidae, Viverridae) From Southwestern France

“…No clinical signs of the disease or abortions have been described in these species, but there is evidence of renal carriage, long-lasting leptospiruria, and associated renal lesions (Roth et al, 1963;Crowell et al, 1977;Schowalter et al, 1981). Leptospiral infection has also been reported in sea otters (Enhydra lutris) and North American river otters (Lontra canadensis; Hanni et al, 2003;Gaydos et al, 2007), small Indian mongoose (Herpestes javanicus auropunctatus; Everard et al, 1983), Asian palm civets (Paradoxurus hermaphroditus ;Gordon Smith et al, 1961), and genets (Genetta spp. ; Sebek et al, 1989).…”