Estuary-associated syndrome in North Carolina: an occupational prevalence study.

Abstract

Atlantic coast estuaries recently have experienced fish kills and fish with lesions attributed to Pfiesteria piscicida and related dinoflagellates. Human health effects have been reported from laboratory exposure and from a 1997 Maryland fish kill. North Carolina has recorded Pfiesteria-related fish kill events over the past decade, but human health effects from environmental exposure have not been systematically investigated or documented here. At the request of the state health agency, comprehensive examinations were conducted in a cross-sectional prevalence study of watermen working where Pfiesteria exposure may occur: waters where diseased or stressed fish were reported from June to September 1997, and where Pfiesteria had been identified in the past. Controls worked on unaffected waterways. The study was conducted 3 months after the last documented Pfiesteria-related fish kill. The goal was to document any persistent health effects from recent or remote contact with fish kills, fish with lesions, or affected waterways, using the 1997 U.S. Centers for Disease Control and Prevention case description for estuary-associated syndrome (EAS). Examinations included comprehensive medical, occupational, and environmental history, general medical, dermatologic, and neurologic examinations, vision testing, and neuropsychologic evaluations. Seventeen of 22 watermen working in affected waters and 11 of 21 in unaffected waters reported exposure to a fish kill or to fish with lesions. We found no pattern of abnormalities on medical, neurologic, neuropsychologic, or NES-2 evaluation. By history, one subject in each group met the EAS criteria, neither of whom had significant neuropsychological impairment when examined. Watermen from affected waterways had a significant reduction in visual contrast sensitivity (VCS) at the midspatial frequencies, but we did not identify a specific factor or exposure associated with this reduction. The cohorts did not differ in reported occupational exposure to solvents (qualitative) or to other neurotoxicants; however, exposure history was not sufficiently detailed to measure or control for solvent exposure. This small prevalence study in watermen, conducted 3 months after the last documented fish kill related to Pfiesteria, did not identify an increased risk of estuary-associated syndrome in those working on affected waterways. A significant difference between the estuary and ocean watermen was found on VCS, which could not be attributed to any specific factor or exposure. VCS may be affected by chemicals, drugs, alcohol, and several developmental and degenerative conditions; it has not been validated as being affected by known exposure to dinoflagellate secretions. VCS should be considered for inclusion in further studies, together with documentation or quantification of its potential confounders, to assess whether it has utility in relationship to dinoflagellate exposure.

Visual contrast sensitivity as a diagnostic tool.

“…We agree that previous publications only associated a VCS deficit with Pfiesteria-inhabited estuary contact, not with active PEAS. The North Carolina study, which associated the VCS deficit with estuarine contact (3,4), was designed to investigate the potential for persistent, estuary-associated health effects (5). Unlike the Maryland study, which involved recent exposure to fish kills and active PEAS (2), members of the North Carolina estuary cohort had no recent fish-kill exposure and were not selected because of complaints of current health effects (5).…”

“…The North Carolina study, which associated the VCS deficit with estuarine contact (3,4), was designed to investigate the potential for persistent, estuary-associated health effects (5). Unlike the Maryland study, which involved recent exposure to fish kills and active PEAS (2), members of the North Carolina estuary cohort had no recent fish-kill exposure and were not selected because of complaints of current health effects (5). The North Carolina study (5) attempted to use the Centers for Disease Control and Prevention (CDC) symptom-based case definition (6) to assess PEAS at remote times of fish kill or lesioned fish contact, times at which VCS data were unavailable (5).…”

“…Unlike the Maryland study, which involved recent exposure to fish kills and active PEAS (2), members of the North Carolina estuary cohort had no recent fish-kill exposure and were not selected because of complaints of current health effects (5). The North Carolina study (5) attempted to use the Centers for Disease Control and Prevention (CDC) symptom-based case definition (6) to assess PEAS at remote times of fish kill or lesioned fish contact, times at which VCS data were unavailable (5). The Virginia study (7) verified the VCS deficit in people contacting estuaries inhabited by "Pfiesteria-like organisms," but reported no active PEAS cases.…”

“…In a study in Virginia, Turf et al (5) did not identify any cases of EAS in the first year of their ongoing prospective cohort study. They observed VCS deficits, which correlated with age, exposure time to estuary waters where Pfiesteria organisms may be found more than 50% of the time, and smoking.…”

“…However, these deficits were not correlated with active (P)EAS, "as no cases were identified during the study. No toxic Pfiesteria events nor changes in neurocognivive function were observed" (5). Data are accumulating that Pfiesteria is enzootic in Atlantic coastal waters, even where ichthyotoxic effects have never been observed.…”