| Abstract | In September 1991, an abnormal number of brown pelicans (Pelecanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus) died in Santa Cruz, California, from acute poisoning attributed to the marine neurotoxin domoic acid (DA). Repeated attempts to isolate viruses or bacteria were unsuccessful, and levels of pesticides (organochlorines and organophosphates) and heavy metals in the seabirds were within normal limits. The only consistent gross and histopathologic lesions observed were hemorrhages and necrosis of the skeletal muscle. Serum blood urea nitrogen and creatinine phosphokinase were elevated in affected birds relative to normal captive birds. The case fatality rate for DA-poisoned pelicans was 69% with more males affected than females. Domoic acid was detected in stomach contents of sick and dead pelicans and cormorants, as well as in the flesh and viscera of northern anchovies (Engraulis mordax) and in plankton samples dominated by Pseudonitzschia australis. Large numbers of P. australis cells were found in the stomachs of both pelicans and anchovies. It appears that the anchovies obtained the toxin through grazing of P. australis, whereupon seabirds became poisoned through the consumption of the anchovies. This is the first documentation of DA poisoning outside of Atlantic Canada, of its presence in herbivorous finfish, and of the diatom P. australis as a suspected producer of DA. |
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