2 research outputs found
Genetic epidemiology of fecal egg excretion during Schistosoma mansoni infection in an endemic area in Minas Gerais, Brazil
Genetic Epidemiology of Fecal Egg Excretion During Schistosoma mansoni Infection in an Endemic Area in Minas Gerais, Brazil
There is considerable variation in the level of fecal egg excretion
during Schistosoma mansoni  infections. Within a single endemic
area, the distribution of egg counts is typically overdispersed, with
the majority of eggs excreted coming from a minority of residents. The
purpose of this study was to quantify the influence of genetic factors
on patterns of fecal egg excretion in a rural study sample in Brazil.
Individual fecal egg excretions, expressed in eggs per gram of feces,
were determined by the Kato-Katz method on stool samples collected on
three different days. Detailed genealogic information was gathered at
the time of sampling, which allowed assignment of 461 individuals to 14
pedigrees containing between 3 and 422 individuals. Using a maximum
likelihood variance decomposition approach, we performed quantitative
genetic analyses to determine if genetic factors could partially
account for the observed pattern of fecal egg excretion. The
quantitative genetic analysis indicated that between 21-37% of the
variation in S. mansoni egg counts was attributable to additive genetic
factors and that shared environment, as assessed by common household,
accounted for a further 12-21% of the observed variation. A maximum
likelihood heritability (h2) estimate of 0.44 ± 0.14 (mean ±
SE) was found for the 9,604 second- and higher-degree pairwise
relationships in the study sample, which is consistent with the upper
limit (37%) of the genetic factor determined in the variance
decomposition analysis. These analyses point to the significant
influence of additive host genes on the pattern of S. mansoni fecal egg
excretion in this endemic area