title: The relative influence of polyparasitism, environment, and host factors on schistosome infection.
abstract: Where prevalence of geohelminths and schistosomes is high, co-infections with multiple parasite species are common. Previous studies have shown that the presence of geohelminths either promotes or is a marker for greater prevalence and intensity of Schistosoma mansoni infections. Some of this apparent synergy may simply represent shared conditions for exposure, such as poor sanitation, and may not suggest a direct biologic interaction. We explored this question in a study of 13,279 school children in Jequié, Bahia, Brazil, with a survey of demographic characteristics and stool examinations. Cross-sectional analysis revealed a statistically significant increase in the prevalence and intensity of S. mansoni infection with increasing numbers of geohelminth species (OR 2.5, 95% CI 1.38-3.64). Less than 20% of the strength of this association was contributed by socioeconomic status or environmental conditions. Thus, polyparasitism itself, as well as intrinsic host factors, appears to produce greater susceptibility to additional helminth infections.
authors.affiliation: School of Nutrition, Federal University of Bahia, Salvador, Bahia, Brazil.
authors.forename: Rita
authors.initials: R
authors.lastname: de Cássia Ribeiro Silva
authors.forename: Maurício Lima
authors.initials: ML
authors.lastname: Barreto
authors.forename: Ana Marlúcia Oliveira
authors.initials: AM
authors.lastname: Assis
authors.forename: Mônica Leila Portela
authors.initials: ML
authors.lastname: de Santana
authors.forename: Isabel M
authors.initials: IM
authors.lastname: Parraga
authors.forename: Mitermayer Galvão
authors.initials: MG
authors.lastname: Reis
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Blanton
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000723:Ancylostomatoidea; D000818:Animals; D001196:Ascariasis / Q000453:epidemiology / Q000469:parasitology; D017164:Ascaris lumbricoides / Q000254:growth & development; D001938:Brazil / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D005243:Feces / Q000469:parasitology; D005260:Female; D006725:Hookworm Infections / Q000453:epidemiology / Q000469:parasitology; D006801:Humans; D008297:Male; D009349:Nematode Infections / Q000453:epidemiology* / Q000469:parasitology*; D010270:Parasite Egg Count; D012552:Schistosomiasis / Q000453:epidemiology* / Q000469:parasitology*; D012737:Sex Factors; D012959:Socioeconomic Factors; D014257:Trichuriasis / Q000453:epidemiology / Q000469:parasitology; D014258:Trichuris / Q000254:growth & development