Protozoal encephalitis is a disease that is also relatively common in otters. This disease involves swelling of the brain which has been found to be caused by several genera of protozoa. Coccidioidomycosis is an infection derived from a soil-borne fungus that is common in dry interior valleys. Cases of this type of infection are limited to populations in San Louis Obispo county. The nature of propagation of the disease is not well understood.
Bacterial infection is another significant cause of otter mortality.
The types of bacteria involved vary significant between the individuals examined. In the final stages of some infections, significant interstital fibrosis has been documented. Recent examinations of otters imported to Japan from Alaska have revealed intestinal parasites. Four species of acanthocephalan of the genus Corynosoma have been recovered from these sea otters. Ecology Sea otter predation has a predictable and broadly generalizable influence on the structure of Alaskan kelp forests.