Abstract

During a period of six days during July, 1978, a group of over 40 adult California sea lions came ashore on beaches in Ventura County, California. All of the animals were located from the surf wash zone to the high tide line. They displayed identical symptoms including paralysis, excessive lacrimation and salivation, absence of a corneal reflex, and occasional severe tonic convulsions. The animals died from a few hours to three days after they beached. Necropsy of seven seals revealed them to be in good flesh and without gross lesions indicating cause for the observed syndrome. Similar histopathology was observed in all cases, believed to be lesions in varying stages of the same disease. The common changes of most significance were in: a) heart-myocarditis and edema, b) liver-periportal inflammation and congestion, c) brain-changes including satellitosis and neuronophagia and d) lung and kidney-congestion. Selected viral and bacterial cultures were negative. Tissues were not exceptionally high in metals, organochlorine or organophosphate residues. Pathology and symptoms are consistent with a viral hepatoencephalopathy.

Notes

Abnormal behavior included lack of vocalizing, circling, paralysis with no response to stimuli and severe terminal tonic convulsions.

Pseudocholinesterase levels were normal. There were no viral inclusion bodies found in the liver.

Brain histology revealed microglial cells accumulated around neurons (satellitosis) which is indicative of toxicity.

They are testing now for heavy metals.

Observers related that many shearwaters were found dead on the beaches at the same time as the sea lions. The condition was likely very acute since observers on a nearby island saw no sick sea lions. The animals likely had no time to get back to their usual haunts but came directly on to the beach.