Population structure of the Jirels: Patterns of mate choice

Proc. Natl. Acad. Sci. U.S.A.

VandeBerg

Subedi

et al. 2002

120

108

Nematode parasites show a characteristic aggregated distribution among hosts. This observation has important implications for pathogenesis, immunology, and control of these infections, but the relative roles of environment and genetics in determining these patterns have remained uncertain. This paper presents the results of the first genome scan for susceptibility to infection with roundworm (Ascaris lumbricoides). Data on 375 genetic markers were generated for each of 444 members of a genetically isolated Nepalese population, the Jirels. Ascaris worm burden as assessed by egg counts was measured in these same individuals by using the Kato Katz thick smear method. The extensive genealogical data available for the population allowed assignment of all 444 individuals to a single pedigree that contained 6,209 pairs of relatives that were informative for genetic analysis. A variance components linkage analysis resulted in the unequivocal localization of two genes (one on chromosome 1 and another on chromosome 13) with clear, significant effects on susceptibility to Ascaris infection. This is the first evidence that individual quantitative trait loci influence variation in Ascaris burden in humans.

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Genes on chromosomes 1 and 13 have significant effects on Ascaris infection

Proc. Natl. Acad. Sci. U.S.A.

VandeBerg

Subedi

et al. 2002

120

108

“…The population has been the subject of extensive population genetic and genetic epidemiologic study for the last 14 years and has this has resulted in detailed knowledge of the pedigree structure of the group. [34][35][36][37][38][39][40][41][42][43][44][45] Family information. Household surveys were performed to obtain demographic, pedigree, and socioeconomic data from each household.…”

Section: Population Materials and Methodsmentioning

confidence: 99%

Genetic analysis of susceptibility to infection with Ascaris lumbricoides.

The American Journal of Tropical Medicine and Hygiene

Subedi

Upadhayay

et al. 1999

107

Abstract. Epidemiologic studies of helminthic infections have shown that susceptibility to these parasites frequently aggregates in families, suggesting the possible involvement of genetic factors. This paper presents a genetic epidemiologic analysis of Ascaris lumbricoides infection in the Jirel population of eastern Nepal. A total of 1,261 individuals belonging to a single pedigree were assessed for intensity of Ascaris infection at two time points. Following an initial assessment in which all individuals were treated with albendazole, a follow-up examination was performed one year later to evaluate reinfection patterns. Three measures of worm burden were analyzed, including eggs per gram of feces, direct worm counts, and worm biomass (weight). For all traits, variance component analysis of the familial data provided unequivocal evidence for a strong genetic component accounting for between 30% and 50% of the variation in worm burden. Shared environmental (i.e., common household) effects account for between 3% and 13% of the total phenotypic variance.

“…In the Jirels, observed population structure effects are probably owing to the residual effects of differential admixture with relatively closely related ancestral populations including Sherpas and Sunwars. Additionally, the relative endogamy of Jirel villages [11,25] and the non-randomness of clan-structured migration [21] lead to a second type of lesser microdifferentiation generating local between-group genetic differences. We appear to have observed some of this between-group genetic variation as relevant for our helminthic infection-related phenotypes.…”

Section: Discussionmentioning

confidence: 99%

“…The study was based in the Jiri region of Dolakha district in the eastern hills of Nepal, and focused on the Jirel ethnic group. Some ethnohistorical accounts and population genetic studies have suggested that this ethnic group is a hybrid population derived from Sunwars and Sherpas [10,11]. Members of the Jirel population were sampled from across seven villages in the Jiri region.…”

Section: Introductionmentioning

confidence: 99%

Host genetics and population structure effects on parasitic disease

Criscione

VandeBerg³

et al. 2012

Phil. Trans. R. Soc. B

Host genetic factors exert significant influences on differential susceptibility to many infectious diseases. In addition, population structure of both host and parasite may influence disease distribution patterns. In this study, we assess the effects of population structure on infectious disease in two populations in which host genetic factors influencing susceptibility to parasitic disease have been extensively studied. The first population is the Jirel population of eastern Nepal that has been the subject of research on the determinants of differential susceptibility to soil-transmitted helminth infections. The second group is a Brazilian population residing in an area endemic for Trypanosoma cruzi infection that has been assessed for genetic influences on differential disease progression in Chagas disease. For measures of Ascaris worm burden, within-population host genetic effects are generally more important than host population structure factors in determining patterns of infectious disease. No significant influences of population structure on measures associated with progression of cardiac disease in individuals who were seropositive for T. cruzi infection were found.