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BIOTOXIN-INDUCED NEUROTOXICITY: AN EMERGING RISK FOR HUMAN HEALTH AND ECOLOGY.
Citation:
Hudnell, K. BIOTOXIN-INDUCED NEUROTOXICITY: AN EMERGING RISK FOR HUMAN HEALTH AND ECOLOGY. Presented at International Neurotoxicology Association, Estoril, Portugal, 6/17-22, 2001.
Description:
The increasing incidence of human illness associated with exposure to biotoxins from harmful algal blooms (HABs) in aquatic environments, and fungi and bacteria on land, may indicate an emerging human-health risk. HABs are reported to be increasing worldwide in frequency, duration and spatial extent in association with increasing aquatic pollution. New HAB species, such as members of the toxic Pfiesteria complex, p. piscicida and p. shumwayae, are being discovered on a regular basis. The US Centers for Disease Control identified a syndrome in humans following estuarine contact around the time of Pfiesteria-associated fish kills, and developed a symptom-based case definition for the condition, Possible Estuary Associated Syndrome (PEAS). Initial research focused on identifying objective indicators of PEAS for use in diagnoses, and on potential treatments.
Prior to the CDC identification of PEAS, EPA assisted the State of North Carolina in a clinical study of watermen working in estuaries with past, but not recent, exposure to fish kills associated with Pfiesteria by adding tests of visual function, including visual contrast sensitivity (VCS). Of the many clinical and laboratory endpoints, only VCS showed a significant deficit in the exposed cohort relative to a matched-control cohort of unexposed watermen. In spite of normal visual acuity, VCS was reduced by about 30% in the watermen working in Pfiesteria-inhabited estuaries, a result independently replicated in Virginia watermen. Shoemaker subsequently studied patients seeking health care at a clinic near Chesapeake Bay, Maryland, estuaries where large Pfiesteria-related fish kills had occurred. Visual function was examined in 77 patients with residential and/or recreational exposure to the estuaries and in 87 patients without estuarine exposure. VCS was significantly reduced in the estuarine-exposed patients, and 37 of those patients met the CDC case definition for PEAS. The 60% VCS loss in the PEAS patients was reversed, and symptoms abated, following 2 weeks of treatment with the toxin-binding polymer, cholestyramine (CSM), a compound known to increase the elimination rate of a variety of toxins. Preliminary results from other populations suggested that the VCS and treatment effects may generalize to many toxins produced by a variety dinoflagellates, cyanobacteria and fungi in marine, fresh water and land environments. Additional data relating biotoxin exposure to adverse human-health effects are needed to assess and prioritize this potential risk in order to formulate scientifically-sound, risk-management strategies. This abstract does not necessarily reflect the views of the Agency.