domoic-acid and Poisoning

The periodic trend to cetacean mass stranding events in the Australian island state of Tasmania remains unexplained. This article introduces the hypothesis that domoic acid poisoning may be a causative agent in these events. The hypothesis arises from the previously evidenced role of aeolian dust as a vector of iron input to the Southern Ocean; the role of iron enrichment in Pseudo-nitzschia bloom proliferation and domoic acid production; and importantly, the characteristic toxicosis of domoic acid poisoning in mammalian subjects leading to spatial navigation deficits. As a pre-requisite for quantitative evaluation, the plausibility of this hypothesis was considered through correlation analyses between historical monthly stranding event numbers, mean monthly chlorophyll concentration and average monthly atmospheric dust loading. Correlation of these variables, which under the domoic acid stranding scenario would be linked, revealed strong agreement (r = 0.80-0.87). We therefore advocate implementation of strategic quantitative investigation of the role of domoic acid in Tasmanian cetacean mass stranding events.

Topics: Animals; Cetacea; Diatoms; Iron; Kainic Acid; Marine Toxins; Poisoning; Seasons; Tasmania

During 2002, 2,239 marine mammals stranded in southern California. This unusual marine mammal stranding event was clustered from April to June and consisted primarily of California sea lions (Zalophus californianus) and long-beaked common dolphins (Delphinus capensis) with severe neurologic signs. Intoxication with domoic acid (DA), a marine neurotoxin produced during seasonal blooms of Pseudo-nitzschia spp., was suspected. Definitively linking harmful algal blooms to large-scale marine mammal mortalities presents a substantial challenge, as does determining the geographic extent, species composition, and potential population impacts of marine mammal die-offs. For this reason, time series cross-correlation analysis was performed to test the temporal correlations of Pseudo-nitzschia blooms with strandings occurring along the southern California coastline. Temporal correlations were identified between strandings and blooms for California sea lions, long-beaked common dolphins, and short-beaked common dolphins (Delphinus delphis). Similar correlations were identified for bottlenose dolphins (Tursiops truncatus) and gray whales (Eschrichtius robustus), but small sample sizes for these species made associations more speculative. The timing of the blooms and strandings of marine mammals suggested that both inshore and offshore foraging species were affected and that marine biotoxin programs should include offshore monitoring sites. In addition, California sea lion-strandings appear to be a very sensitive indicator of DA in the marine environment, and their monitoring should be included in public health surveillance plans.

Topics: Animals; Brain Diseases; California; Environmental Monitoring; Epidemiological Monitoring; Eutrophication; Female; Food Chain; Kainic Acid; Male; Marine Toxins; Mortality; Neurotoxins; Poisoning; Sea Lions; Seasons

Harmful algal blooms are increasing worldwide, including those of Pseudo-nitzschia spp. producing domoic acid off the California coast. This neurotoxin was first shown to cause mortality of marine mammals in 1998. A decade of monitoring California sea lion (Zalophus californianus) health since then has indicated that changes in the symptomatology and epidemiology of domoic acid toxicosis in this species are associated with the increase in toxigenic blooms. Two separate clinical syndromes now exist: acute domoic acid toxicosis as has been previously documented, and a second novel neurological syndrome characterized by epilepsy described here associated with chronic consequences of previous sub-lethal exposure to the toxin. This study indicates that domoic acid causes chronic damage to California sea lions and that these health effects are increasing.

Topics: Animals; California; Diatoms; Female; Hippocampus; Kainic Acid; Male; Marine Toxins; Neurotoxins; Parahippocampal Gyrus; Poisoning; Sea Lions; Seizures; Time Factors

Eighty-one Californian sea lions (Zalophus californianus) with signs of domoic acid toxicity stranded along the coast of California in 1998 when there were blooms of the domoic acid-producing alga Pseudonitzschia australis off-shore. In 2000, a further 184 sea lions stranded with similar clinical signs, but the strandings occurred both during detectable algal blooms and after the blooms had subsided. The clinical signs in these 265 Californian sea lions included seizures, ataxia, head weaving, decreased responsiveness to stimuli and scratching behaviour. Affected animals had high haematocrits, and eosinophil counts, and high activities of serum creatine kinase. They were treated supportively by using fluid therapy, diazepam, lorazepam and phenobarbitone. Fifty-five of the 81 sea lions (68 per cent) affected in 1998 and 81 of the 184 (44 per cent) affected in 2000 died despite the treatment. Three of the 23 sea lions which survived in 1998 were tracked with satellite and radiotransmitters; they travelled as far south as San Miguel Island, California, and survived for at least three months. Eleven of the 129 animals which were released stranded within four months of being released.

Topics: Animals; California; Diatoms; Eutrophication; Female; Kainic Acid; Male; Marine Toxins; Neurotoxins; Poisoning; Prognosis; Sea Lions; Survival Analysis

Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans.

Topics: Animals; Bivalvia; Brain Diseases; California; Chromatography, Liquid; Diatoms; Eutrophication; Fishes; Food Chain; Humans; Kainic Acid; Marine Toxins; Mass Spectrometry; Mortality; Neurotoxins; Poisoning; Sea Lions

Domoic acid was found to be responsible for an isolated event involving the massive death of brown pelicans (Pelecanus occidentalis) in January 1996, at the tip of the Baja California peninsula. The death of these sea birds was the result of feeding on mackerel (Scomber japonicus) contaminated by domoic acid-producing diatoms (Pseudonitzschia sp.). The number of dead birds (150 animals) found during a period of 5 days caused alarm and called for a governmental task force that would help to implement emergency measurements to protect other species of bird. Also, local canneries were inspected to verify the safety of their recent production and prevent the toxin entering the human market. Fortunately, the timing, response and coordination of this task force enabled identification of the origin and nature of the toxin that provoked such a phenomenon. Future monitoring is recommended to avoid a larger impact of domoic acid spreading and the occurrence of similar toxic events.

Topics: Animals; Bird Diseases; Birds; Chromatography, High Pressure Liquid; Diatoms; Fishes; Kainic Acid; Marine Toxins; Mexico; Mice; Neuromuscular Depolarizing Agents; Poisoning