Neoplasia has been occasionally observed in northern (Enhydra lutris kenyoni) and southern sea otters (Enhydra lutris nereis) including two cases of uterine leiomyoma, malignant and incidental seminomas, osteosarcoma, oligodendroma, possible parathyroid carcinoma and three cases of sarcomas in free-living sea otters. Lymphosarcoma and one animal with concurrent cholangiocellular adenocarcinoma, leiomyoma and pheochromocytoma have been reported in captive northern sea otters.
During the past 4 years, complete necropsies were performed as part of a cooperative disease screening program on 124 northern sea otters collected moribund or freshly dead from South-central Alaska. 85% of these animals (n = 84) were found by an active volunteer stranding network operating in Kachemak Bay, AK. Neoplasia was the cause of death in 2 (1.6%) of the total number of sea otters examined. Both of these animals were from Kachemak Bay and had highly metastatic, poorly differentiated neoplasia involving the liver, spleen and lymph nodes. Histopathologic and immunohistochemistry examination of the neoplastic tissues was performed.
The tumor in one otter was identified as a hemangiosarcoma and was associated with bacterial sepsis (Salmonella sp). The second was a poorly differentiated carcinoma of unknown origin. This animal also had an incidental finding of uterine fibroleiomyoma. Future investigation will include PCR for herpesvirus, calicivirus, adenovirus, and papillomavirus and immunohistochemistry for gammaherpesvirus.
We would like to thank the staff of the Alaska SeaLife Center including Carrie Goertz, Millie Gray, Tim Lebling and Carol Stephens. Funding for tissue analysis and additional assistance was provided by our collaborators in the Sea Otter Disease Screening and Biosampling Program including Jim Bodkin and Dan Mulcahy, USGS and Verena Gill and Angela Doroff, USFWS and by grants from the Oiled Wildlife Care Network and the Minnesota Zoo.