Genetic and Household Determinants of Predisposition to Human Hookworm Infection in a Brazilian Community

Institute of Integrative and Comparative Biology, University of Leeds, Leeds, United Kingdom.
The Journal of Infectious Diseases (Impact Factor: 6). 09/2010; 202(6):954-61. DOI: 10.1086/655813
Source: PubMed


Predisposition to heavy or light human hookworm infection is consistently reported in treatment-reinfection studies. A significant role for host genetics in determining hookworm infection intensity has also been shown, but the relationship between host genetics and predisposition has not been investigated.
A treatment-reinfection study was conducted among 1302 individuals in Brazil. Bivariate variance components analysis was used to estimate heritability for pretreatment and reinfection intensity and to estimate the contribution of genetic and household correlations between phenotypes to the overall phenotypic correlation (ie, predisposition).
Heritability for hookworm egg count was 17% before treatment and 25% after reinfection. Predisposition to heavy or light hookworm infection was observed, with a phenotypic correlation of 0.34 between pretreatment and reinfection intensity. This correlation was reduced to 0.23 after including household and environmental covariates. Genetic and household correlations were 0.41 and 1, respectively, and explained 88% of the adjusted phenotypic correlation.
Predisposition to human hookworm infection in this area results from a combination of host genetics and consistent differences in exposure, with the latter explained by household and environmental factors. Unmeasured individual-specific differences in exposure did not contribute to predisposition.

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    • "A multi-factorial study of the intensity of hookworm infection in Brazil also found effects of an individual's household (0.16 and 0.095 for primary and re-infection intensity), as well as similar sized genetic effects (0.16 and 0.24 for primary and reinfection intensity) (Quinnell et al., 2010) (Section 4.1). There was a strong pre-disposition to re-infection among the individuals, which was most convincingly explained by shared household effects, which included availability of sanitation, living density and socio-economic status (Quinnell et al., 2010). Analysis of the risk factors for hookworm and S. mansoni co-infection in Brazil likewise found that household factors (socio-economic status, living density), as well as larger-scale geographical effects, were associated with co-infection (Pullan et al., 2008). "
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