By CHRIS DIXON

Published: June 15, 2004

LOS ANGELES - Sea otters, dead and alive, have been washing up on the California coast in record numbers for two springs, and scientists say they are closer to solving the mystery.

The principal culprits, the scientists say, are toxoplasma gondii and sarcocystis neurona, parasites that can cause fatal diseases in the brains and nervous systems of otters and other animals. Toxoplasma gondii, which can affect humans too, spreads its hardy spores through cat feces, while sarcocystis neurona is spread through opossum feces. [...]

[...] Dr. [Melissa] Miller said she suspected that the otters encountered the parasite by eating shellfish that carried it. The shellfish, she said, could have picked up sarcocystis neurona from the runoffs of heavy rains in February. Runoff has been shown to transport cat feces infected with toxoplasma gondii to the ocean, where the spores are eaten by shellfish, and then by otters, she said. Her theory is that the water might have carried opossum feces in the same way.

Studies to investigate this theory are being conducted, she said.

Opossums are not native to California. According to the California Department of Fish and Game, they were probably imported from Virginia in the early 1900's so that people could hunt them. [...]