DIRECT ANALYSIS OF SCHISTOSOMA MANSONI POPULATION STRUCTURE USING AGGREGATED INDIVIDUALS FROM LABORATORY STRAINS AND TOTAL FECAL EGG SAMPLING

摘要

Many parasite populations are difficult to sample because they are non-uniformly distributed between several host species and are often not easily collected from the living host, limiting sample size and possibly distorting the representation of the population. For the parasite Schistosoma mansoni, we investigated the use of the aggregated eggs found in the stool of infected individuals as a simple and representative sample. Previously, we demonstrated that microsatellite allele frequencies can be accurately estimated from pooled DNA of cloned S. mansoni adults, and we show here that genotyping parasite populations from reproductively isolated laboratory strains can be used to identify these specific populations based on characteristic patterns of allele frequencies, as observed by polyacrylamide gel electrophoresis and automated sequencer analysis of fluorescently labeled PCR products. In addition, microsatellites used to genotype aggregates of eggs collected from stools of infected individuals produced results consistent with the geographic distribution of the samples. Direct analysis of total stool eggs can be an important approach to questions of population genetics for this parasite by increasing the sample size to thousands per individual and reducing bias.