NEW APPROACHES FOR THE CONTROL AND ERADICATION OF SCHISTOSOMIASIS IN VENEZUELA

Schistosomiasis in America with the exception of Brazil, behaves as a chronic mild disease with few clinical manifestations due to low paras ite burden. These features restrict the clinical and parasitological d iagnosis. The most commonly used stool examination method, Kato-Katz, becomes insensitive when the majority of individuals excrete less than 100 eggs/g of feces. In view that antigen-detecting techniques have h ot been able to reveal light infections, the antibody detecting assays remain as a very valuable diagnostic tool for epidemiological surveil lance. The Venezuelan Schistosomiasis Research Group (CECOICE) has des igned a mass chemotheraphy strategy based on sero-diagnosis. Since blo od sampling is one of the important limitating factors for large seroe pidemiological trials we developed a simple capillary technique that s uccessfully overcomed most of the limitations of blood drawing. In thi s sense, ELISA seems to be the most adecuate test for epidemiological studies. Soluble egg Schistosoma mansoni antigen (SEA) has been largel y used in Venezuela. The sensitivity of ELISA-SEA in our hands is 90%, moreover its specificity reach 92% when populations from non-endemic areas but heavily infected with other intestinal parasites are analyze d. The Schistosomiasis Control Program is currently carrying out the s urveillance of endemic areas using ELISA-SEA as the first screening me thod, followed by the Circumoval Precipitin test for validation assay. The results with these two serological techniques allowed us to defin ed the criteria of chemotherapy in populations of the endemic areas. O n the search of better diagnostic technique, Alkaline Phosphatase Immu noenzyme Assay (APIA) is being evaluated in field surveys.