A Possible Genetic Factor Influencing Protection from Infection with Ascaris lumbricoides in Nigerian Children

Abstract

An epidemiological study of Ascaris lumbricoides infections was carried out in primary school children aged 5-16 yr from Ile-Ife, Nigeria. Intensity of infection was assessed directly by means of counting worms passed during a 48-hr period after chemotherapy. Reinfection patterns of A. lumbricoides were assessed at 2 6-mo intervals and statistical evidence of predisposition to infection status was obtained. An investigation of 3 groups of children who were judged to be predisposed not to be infected, to be lightly infected, and to be heavily infected was undertaken. Assignment to the groups was based upon the mean worm burden plus 1 SD above the mean, measured at 2 6-mo intervals. The distribution of class I human leucocyte antigens among the 3 groups of children was described. None of the children who were predisposed to remain uninfected was found to possess the A30/31 antigens in contrast to those children who remained infected.

Localization of Multiple Quantitative Trait Loci Influencing Susceptibility to Infection withAscaris lumbricoides

“…The possibility that this commonly observed overdispersion is due to host genetic factors has been explored in a number of studies. For example, a study of Nigerian children aged 5-16 years found evidence for a role of the major histocompatibility complex in determining patterns of Ascaris infection [5].Most previous genetic studies of soil-transmitted helminthic infections [6 -12] have focused on relatively small sample sizes and simple pedigree structures, as shown in table 1. The majority of these studies were quantitative genetic assessments of the heritabilities of helminth infections as assessed by eggs per gram of feces, with between 0% and 39% of the variation being attributable to genetic factors.…”

Genetic analysis of susceptibility to infection with Ascaris lumbricoides.

“…An analysis of A. lumbricoides worm loads in Nigerian children suggested the involvement of the major histocompatibility complex (MHC) in determining resistance to infection. 28 Similarly, the MHC has been associated with severity of outcome in schistosomiasis. 29 Although compelling, such association studies of candidate genes have potentially major statistical problems that can lead to false-positive results.…”

Investigating the underlying mechanism of resistance to Ascaris infection

“…While the generative mechanisms of predisposition are currently unknown, it is believed that host genetics may play a major role [56][57][58][59][60][61]. Familial patterning to Ascaris infection has been M A N U S C R I P T indicates that the genetic factors influencing the host's capacity to respond protectively to infection are polygenic, specified by many minor susceptibility genes rather than primarily by a few major loci [62].…”