The last fifteen years of schistosomiasis in Venezuela: Features and evolution

Control of schistosomiasis in Venezuela has been a topic of major interest and controversy among the metaxenic parasitosis. a small area of transmissi on of approximately 15,000 km(2) was thought to be eradicated some years ag o. However, some epidemiological characteristics of our transmission area h ave limited the success on the way toward eradication. Since 1945, when the Schistosomiasis Control Program started, the prevalence in the endemic are a has decreased from 14% in 1943 to 1.4% in 1996. Until 1982, the surveilla nce of active cases was based on massive stool examination. Since then, the Schistosomiasis Research Group (SRG) recommended the additional use of ser ologic tests in the Control Program and the selective or massive chemothera py depending on serological and parasitological prevalence of each communit y. At present, the real prevalence is underestimated due to the fact that a pproximately 80% of the individuals eliminate less than 100 eggs/g of feces . Those persons could be responsible for the maintenance of the foci going on and therefore limiting the impact of the control measures. Efforts of the SRG are being oriented toward improvement of immunodiagnosti c tests by using defined antigens (enzymes) and chemically synthesized pept ides, derived from relevant molecules of the parasite, either for antibodie s or antigens search. On the other hand, introduction of snail competitors has been a biological weapon in the control of the intermediate host in cer tain areas. However, the recent reinfestation of water courses by Biomphala ria glabrata, the increased prevalence in some areas, together with importa nt administrative changes at the Control Program of the Minister of Health, have arisen new questions and doubts, challenging the eradication strategy proposed during the last decade.