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INVESTIGATION OF SERUM MICROCYSTIN CONCENTRATIONS AMONG DIALYSIS PATIENTS, BRAZIL, 1996
Citation:
Hilborn, E D. INVESTIGATION OF SERUM MICROCYSTIN CONCENTRATIONS AMONG DIALYSIS PATIENTS, BRAZIL, 1996. Presented at Water Quality & Public Health in Latin America, Rio de Janeiro, Brazil, November 5-7, 2001.
Description:
Investigation of Serum Microcystin Concentrations Among Dialysis Patients, Brazil, 1996
Elizabeth D. Hilborn 1, Wayne W. Carmichael 2, Sandra M.F.O. Azevedo 3
1- USEPA/ORD/NHEERL, Research Triangle Park, NC
2- Wright State University, Dayton, OH
3- Federal University, Rio de Janeiro, Brazil
Background: Beginning in February 1996, an outbreak of fatal cyanobacterial toxin intoxications occurred among dialysis patients in Caruaru, Brazil. Previous reports have discussed the circumstances of exposure and the health consequences of microcystin intoxication. The term ?Caruaru syndrome' (CS) was created during this outbreak to describe the typical clinical presentation of acute hepatic injury due to cyanotoxins, including microcystin. Animal exposure studies indicate that free microcystin concentrations diminish rapidly in the blood. This report will provide: 1) preliminary results, 2) outline the work in progress to examine a larger cohort than originally reported, and 3) to analyze more serum samples for microcystin concentrations as a proposed biomarker of exposure to this toxin.
Methods: Serum samples were gathered by Brazilian Health authorities and the U.S. Centers for Disease Control and Prevention during and after the outbreak of intoxications. Serum from 91 exposed and 34 unexposed controls are archived at Wright State University. To date 47 serum samples have been analyzed for the presence of microcystin using enzyme-linked immunosorbant assay (ELISA), high performance liquid chromatography (HPLC), or liquid chromatography/mass spectrometry (LC/MS). Descriptive and statistical analysis of existing data from the exposed patient cohort was performed.
Results: Of 186 total exposed patients, 174 had age data available; mean age was 43 years (range 14-83 years). There were 107 males (58%) of the 183 patients for whom gender was known. Of 146 patients with symptom data, 117 (80%) experienced symptoms of illness after exposure. Of 186 patients, 76 (41%) were recorded as deceased by July 30, 1997. In 50 (83%) of 60 patients with a recorded cause of death, death was attributed to CS; their date of death ranged from February 20, 1996 to September 15, 1996 (median 3/24/96). Of 47 total serum samples, concentrations of microcystin ranged from 0.0 - 8.1 ng/mL (mean=2.2 ng/mL, median=1.2 ng/mL). No significant differences were found (by t-test) in mean serum microcystin levels among those with or without symptoms of illness, nor among those with cause of death listed as CS vs. those with other causes of death. Elevated serum microcystin concentrations persist above the mean through mid-April in the larger exposed patient cohort. No microcystin was detected in control serum or liver samples. Serum and liver microcystin concentrations were poorly correlated in those 13 patients with both specimens collected.
Conclusions:
Serum microcystin concentrations may reflect short term exposure only; these results suggest ongoing patient exposure through mid-April, 1996. Serum and liver microcystin concentrations were poorly correlated; this may be due to differing collection dates, and/or ongoing exposure. Unknown host factors may mediate clinical response to intoxication.
Future work will involve 1) analysis of 44 more patient serum samples; 2) the development of an analytic method that will measure both bound and unbound microcystin; 3) the application of a commercial ELISA designed to detect microcystins in water for use with human serum and liver samples; and 4) reassessment of potential associations of serum microcystin concentrations with clinical outcomes in this larger cohort.
The views expressed in this abstract are those of the individual authors and do not necessarily reflect the views and policies of the U.S. Environmental Protection Agency.