title: Long-term effect of mass chemotherapy, transmission and risk factors for Schistosoma mansoni infection in very low endemic communities of Venezuela.
abstract: The prevalence of Schistosoma mansoni infection in Venezuela has changed from high to low due mostly to successful control activities, including mass chemotherapy and molluscicide applications. This study examined the impact of mass chemotherapy on S. mansoni transmission and risk factors for infection 12 years after administration of praziquantel in Venezuela. Two relatively isolated rural communities were studied, one with snail control (Manuare) and the second without (Los Naranjos). A cross-sectional survey of randomly selected households included 226 (Manuare) and 192 (Los Naranjos) consenting participants. S. mansoni prevalence was determined using a combination of coprological (Kato-Katz) and serological (circumoval precipitin test, alkaline phosphatase immunoassay and Western blot) tests. Data on epidemiological and socioeconomic risk factors were obtained through individual structured interviews. Univariate analysis and multivariate logistic regression models identified independent risk factors for infection. Water sites were examined for the presence of Biomphalaria glabrata snails. Only one participant was positive by coprology. The overall prevalences according to the combined tests were 32.7% in Manuare and 26.6% in Los Naranjos. Lower prevalences (12.7% in Manuare and 13.2% in Los Naranjos) were found in children <12 years of age representing those born after mass chemotherapy. Social demographic variables associated with infection in both communities were older age (>25 years), contact with specific water sites, and being a farmer/non-specialised worker. Mass treatment with praziquantel applied once to endemic communities led to an important and long-lasting sustained reduction of S. mansoni infections independent of the application of snail control. A degree of low active transmission of S. mansoni persisted in the treated areas which was associated with similar factors in both communities.
authors.affiliation: Faculty of Earth, Life Sciences, VU University of Amsterdam, Amsterdam, The Netherlands; Department of Parasitology, Faculty of Health Sciences, Universidad de Carabobo, Valencia, Venezuela.
authors.forename: Stefanie N
authors.initials: SN
authors.lastname: Hofstede
authors.affiliation: Department of Parasitology, Faculty of Health Sciences, Universidad de Carabobo, Valencia, Venezuela; Department of Medical Microbiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
authors.forename: Adriana
authors.initials: A
authors.lastname: Tami
authors.affiliation: Faculty of Earth, Life Sciences, VU University of Amsterdam, Amsterdam, The Netherlands; Department of Parasitology, Faculty of Health Sciences, Universidad de Carabobo, Valencia, Venezuela.
authors.forename: Genevieve A F S
authors.initials: GA
authors.lastname: van Liere
authors.affiliation: Unidad de Trematodiasis, Center for Microbiology and Cellular Biology, Instituto Venezolano de Investigaciones Científicas, Altos de Pipe, Miranda State, Venezuela.
authors.forename: Diana
authors.initials: D
authors.lastname: Ballén
authors.affiliation: Department of Parasitology, Faculty of Health Sciences, Universidad de Carabobo, Valencia, Venezuela. Electronic address: rincani@uc.edu.ve.
authors.forename: Renzo N
authors.initials: RN
authors.lastname: Incani
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D011223:Praziquantel / Q000627:therapeutic use; D015995:Prevalence; D012307:Risk Factors; D012424:Rural Population; D012555:Schistosomiasis mansoni / Q000188:drug therapy / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission; D012908:Snails / Q000469:parasitology; D012959:Socioeconomic Factors; D014687:Venezuela / Q000453:epidemiology; D055815:Young Adult
chemical_list: D011223:Praziquantel
keywords: Mass chemotherapy; Praziquantel; Prevalence; Risk factors; Schistosoma mansoni; Transmission; Venezuela