title: The relative contribution of immigration or local increase for persistence of urban schistosomiasis in Salvador, Bahia, Brazil.
abstract: Urbanization is increasing across the globe, and diseases once considered rural can now be found in urban areas due to the migration of populations from rural endemic areas, local transmission within the city, or a combination of factors. We investigated the epidemiologic characteristics of urban immigrants and natives living in a neighborhood of Salvador, Brazil where there is a focus of transmission of Schistosoma mansoni. In a cross-sectional study, all inhabitants from 3 sections of the community were interviewed and examined. In order to determine the degree of parasite differentiation between immigrants and the native born, S. mansoni eggs from stools were genotyped for 15 microsatellite markers. The area received migrants from all over the state, but most infected children had never been outside of the city, and infected snails were present at water contact sites. Other epidemiologic features suggested immigration contributed little to the presence of infection. The intensity and prevalence of infection were the same for immigrants and natives when adjusted for age, and length of immigrant residence in the community was positively associated with prevalence of infection. The population structure of the parasites also supported that the contribution from immigration was small, since the host-to-host differentiation was no greater in the urban parasite population than a rural population with little distant immigration, and there had been little differentiation in the urban population over the past 7 years. Public health efforts should focus on eliminating local transmission, and once eliminated, reintroduction from distant migration is unlikely.
authors.affiliation: Case Western Reserve University, Centre for Global Health and Diseases, Cleveland, Ohio, United States of America.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Blanton
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil; Bahiana School of Medicine and Public Health, Salvador, Bahia, Brazil.
authors.forename: Lúcio M
authors.initials: LM
authors.lastname: Barbosa
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil.
authors.forename: Eliana A
authors.initials: EA
authors.lastname: Reis
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil.
authors.forename: Theomira M
authors.initials: TM
authors.lastname: Carmo
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil.
authors.forename: Cláudio R A
authors.initials: CR
authors.lastname: Dos Santos
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil.
authors.forename: Jackson M
authors.initials: JM
authors.lastname: Costa
authors.affiliation: Case Western Reserve University, Centre for Global Health and Diseases, Cleveland, Ohio, United States of America.
authors.forename: Peace T
authors.initials: PT
authors.lastname: Aminu
authors.affiliation: Case Western Reserve University, Centre for Global Health and Diseases, Cleveland, Ohio, United States of America.
authors.forename: Walter A
authors.initials: WA
authors.lastname: Blank
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil; Post-graduate Program in Regional and Urban Development, UNIFACS (Universidade Salvador), Imbuí, Salvador, Bahia, Brazil.
authors.forename: Renato Barbosa
authors.initials: RB
authors.lastname: Reis
authors.affiliation: Center for Control of Zoonoses, Municipal Secretariat of Health, Salvador, Bahia, Brazil.
authors.forename: Isabel C
authors.initials: IC
authors.lastname: Guimarães
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil.
authors.forename: Luciano K
authors.initials: LK
authors.lastname: Silva
authors.affiliation: Gonçalo Moniz Research Center, Oswaldo Cruz Foundation, Salvador, Bahia, Brazil; Bahiana School of Medicine and Public Health, Salvador, Bahia, Brazil; Federal University of Bahia Faculty of Medicine, Sede Mater Praça XV de novembro, s/n-Largo do Terreiro de Jesus, Salvador, Bahia, Brazil.
authors.forename: Mitermayer G
authors.initials: MG
authors.lastname: Reis
mesh_terms: D000328:Adult; D000818:Animals; D001938:Brazil / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004641:Emigration and Immigration; D005243:Feces / Q000469:parasitology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012550:Schistosoma mansoni / Q000235:genetics; D012552:Schistosomiasis / Q000453:epidemiology* / Q000209:etiology; D014505:Urban Population