Domoic Acid Toxicity in California Sea Lions (Zalophus californianus) Stranded Along the Central California Coast, May-October 1998

Between May 15 and June 19, 1998, 70 California sea lions (Zalophus californianus) and one northern fur seal (Callorhinus ursinus) stranded along the central California coast from San Luis Obispo to San Mateo County. Of these 70 animals, 54 were adult females, with 27 (50 %) pregnant; three were subadult females; two were juvenile females; one was a yearling female; six were subadult males and four were juvenile males (Appendix 1). All animals were in good nutritional condition and displayed similar clinical signs that were predominantly neurological. The animals had severe seizures that either became increasingly frequent, resulting in opisthotonus, then death, or became less frequent with the animals showing ataxia and decreased responsiveness to stimuli between seizures and eventually becoming clinically normal. Forty-eight of the 70 animals (69 %) died despite treatment.