Evidence of high genetic diversity among parasite populations in a schistosomiasis hotspot

TL;DR

This study finds high genetic diversity in Schistosoma mansoni parasites, which could affect drug resistance and control efforts in schistosomiasis-endemic areas.

Contribution

The study provides new insights into the genetic structure and diversity of S. mansoni populations under treatment using microsatellite markers.

Findings

High genetic diversity was observed with significant gene flow among parasite populations.

Private alleles and high heterozygosity suggest potential for drug resistance spread.

Low population structuring indicates that geographic barriers do not significantly influence genetic patterns.

Abstract

Genetic diversity in Schistosoma mansoni populations can impact the prevalence of resistance-conferring alleles, affecting treatment outcomes and control measures. Understanding how parasites are structured across and within populations is important to monitor and manage treatment impacts and the spread of drug resistance. This study assessed the genetic diversity and structure of S. mansoni populations under treatment using multi-locus microsatellite markers. Egg-positive stool samples from school-aged children in schistosomiasis-endemic communities were analyzed to obtain a binary matrix for GenAlEx 6.502 analysis. The markers were 78.57% polymorphic, with a mean allele number ranging from 2.50 to 4.75. Average population metrics were as follows: different alleles (Na) = 3.179, effective alleles (Ne) = 2.282, expected heterozygosity (He) = 0.442, and genetic identity (I) = 0.800, indicating high diversity. Diversity indices were particularly high in Tomefa (I = 0.931, He = 0.499), Manheam (I = 1.074, He = 0.557), and Adakope (I = 0.778, He = 0.448). Analysis of molecular variance revealed low differentiation among populations (4% of total variance, P = 0.001) and high differentiation among individuals (88% of total variance, P = 0.001), with FST = 0.04 and high gene flow (Nm = 5.959). A neighbor-joining tree and principal coordinate analysis indicated low population structuring. The Mantel test showed no significant correlation between genetic and geographic distances (r = 0.006, P = 0.148). The findings suggest high genetic diversity and gene flow, supporting the potential spread of alleles that may confer traits like drug resistance. An integrated approach is needed to achieve sustainable control of schistosomiasis.

This study is crucial as it provides a detailed analysis of Schistosoma mansoni genetic diversity and population structure in schistosomiasis-endemic communities under treatment. By employing multi-locus microsatellite markers, the research highlights significant genetic variation within and among populations, revealing high levels of genetic diversity and gene flow, as well as the presence of private alleles. These findings emphasize the potential for the emergence and spread of drug resistance and virulence traits, which can impact treatment efficacy and control measures. The absence of significant geographic isolation in population structure further emphasizes the need for a comprehensive approach to schistosomiasis control, as genetic factors rather than geographic barriers may drive resistance dynamics. This study informs strategies for sustainable control by integrating genetic insights into disease management efforts.

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