Parasitic Infections Causing Sea Otter Deaths

by Amanda Katz

A study recently conducted by University of California (UC) researchers to determine why an unusually large number of sea otters are dying off the coast of California has revealed that parasitic infections are responsible for many of the deaths.

The sea otter population of California has been dwindling since 1995 and is now only about 2,000. Since January, the bodies of more than 100 dead sea otters have been found along the coastline of the state. Many of the animals died at a time when they would have been most likely to reproduce - between the ages of 4 and 9.

"We are very concerned that the otters are dying so frequently of diseases," said UC-Davis Wildlife Health Center Director Jonna Mazet, DVM. "This indicates that the ecosystem is very unhealthy."

"The numbers are high enough that (this is) a major concern for the population," California Department of Fish and Game veterinarian Dr. David Jessup stated.
Protozoa called Toxoplasma gondii and Sarcocystis neurona were among the parasites found to be causing the deaths.

"(Toxoplasma gondii) invades the otter’s brain and can cause neurological problems such as seizures," said UC-Davis Wildlife Health Center veterinarian Dr. Christine Kreuder. "That could make the otters confused and disabled. They would be less able to evade sharks, more likely to swim to unprotected offshore waters and more likely to shake and twitch (and thus) attract sharks."

The researchers do not know what is causing the protozoa, which naturally can be found only in cat and opossum feces, to be present in waters used by sea otters. However, the scientists suspect storm drain runoff.

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