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Two-year longitudinal survey reveals high genetic diversity of Schistosoma mansoni with adult worms surviving praziquantel treatment at the start of mass drug administration in Uganda.

ABSTRACT: BACKGROUND:A key component of schistosomiasis control is mass drug administration with praziquantel. While control interventions have been successful in several endemic regions, mass drug administration has been less effective in others. Here we focus on the impact of repeated praziquantel treatment on the population structure and genetic diversity of Schistosoma mansoni. METHODS:We examined S. mansoni epidemiology, population genetics, and variation in praziquantel susceptibility in parasites isolated from children across three primary schools in a high endemicity region at the onset of the Ugandan National Control Programme. Children were sampled at 11 timepoints over two years, including one week and four weeks post-praziquantel treatment to evaluate short-term impacts on clearance and evidence of natural variation in susceptibility to praziquantel. RESULTS:Prevalence of S. mansoni was 85% at baseline. A total of 3576 miracidia larval parasites, isolated from 203 individual children, were genotyped at seven loci. Overall, genetic diversity was high and there was low genetic differentiation, indicating high rates of parasite gene flow. Schistosome siblings were found both pre-treatment and four weeks post-treatment, demonstrating adult worms surviving treatment and natural praziquantel susceptibility variation in these populations at the beginning of mass drug administration. However, we did not find evidence for selection on these parasites. While genetic diversity decreased in the short-term (four weeks post-treatment), diversity did not decrease over the entire period despite four rounds of mass treatment. Furthermore, within-host genetic diversity was affected by host age, host sex, infection intensity and recent praziquantel treatment. CONCLUSIONS:Our findings suggest that praziquantel treatments have short-term impacts on these parasite populations but impacts were transient and no long-term reduction in genetic diversity was observed. High gene flow reduces the likelihood of local adaptation, so even though parasites surviving treatment were observed, these were likely to be diluted at the beginning of the Ugandan National Control Programme. Together, these results suggest that MDA in isolation may be insufficient to reduce schistosome populations in regions with high genetic diversity and gene flow.

SUBMITTER: Faust CL

PROVIDER: S-EPMC6935072 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Two-year longitudinal survey reveals high genetic diversity of Schistosoma mansoni with adult worms surviving praziquantel treatment at the start of mass drug administration in Uganda.

Faust Christina L CL Crotti Marco M Moses Arinaitwe A Oguttu David D Wamboko Aidah A Adriko Moses M Adekanle Elizabeth K EK Kabatereine Narcis N Tukahebwa Edridah M EM Norton Alice J AJ Gower Charlotte M CM Webster Joanne P JP Lamberton Poppy H L PHL

Parasites & vectors 20191227 1

<h4>Background</h4>A key component of schistosomiasis control is mass drug administration with praziquantel. While control interventions have been successful in several endemic regions, mass drug administration has been less effective in others. Here we focus on the impact of repeated praziquantel treatment on the population structure and genetic diversity of Schistosoma mansoni.<h4>Methods</h4>We examined S. mansoni epidemiology, population genetics, and variation in praziquantel susceptibility ...[more]

PMID: 31881923

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Project description:Background: Treatment and morbidity control of schistosomiasis relies on a single drug, praziquantel. Therefore, there is a pressing need to explore the effects of PZQ on the parasites at the molecular level and to pursue alternative and/or or synergistic drugs against schistosomiasis. Methodology: We used a custom-designed Schistosoma mansoni oligo-microarray to explore the effects of a sublethal dose of praziquantel on S. mansoni adult worms’ gene expression. We used functional analysis of gene interaction networks to identify differentially expressed genes that are known targets of other drugs already tested in humans for diverse disease conditions. Omeprazole, a proton pump inhibitor drug that is widely prescribed, was tested in combination with praziquantel. We comparatively assessed the efficacy of praziquantel or omeprazole alone and in combination against S. mansoni adult worms in vitro over a period of 120 hours. Principal Findings: We identified sets of genes that were affected by praziquantel on both paired and unpaired females, however with opposite gene expression patterns (up-regulated in paired and down-regulated in unpaired females), indicating that the transcriptomics changes induced by praziquantel are heavily influenced by the mating status. We also identified genes that were similarly affected by praziquantel in males and females. The use of sublethal doses of praziquantel together with omeprazole showed a significantly enhanced worm mortality in vitro compared to praziquantel alone, thus evidencing a synergic effect. Conclusions: Functional analysis of gene interaction networks is an important approach to identify genes whose expression is affected by one drug and that are at the same time known targets of other drugs already tested in humans for diverse disease conditions, thus pointing the latter as possible synergic drugs. Combined treatment with omeprazol increases the efficacy of praziquantel against S. mansoni adult worms in vitro, and additional in vivo studies are warranted.

Project description:Mass drug administration of praziquantel is the World Health Organization's endorsed control strategy for schistosomiasis. A decade of annual treatments across sub-Saharan Africa has resulted in significant reductions of infection prevalence and intensity levels, although 'hotspots' remain. Repeated drug treatments place strong selective pressures on parasites, which may affect life-history traits that impact transmission dynamics. Understanding drug treatment responses and the evolution of such traits can help inform on how to minimise the risk of drug resistance developing, maximise sustainable control programme success, and improve diagnostic protocols.We performed a four-generation Schistosoma mansoni praziquantel selection experiment in mice and snails. We used three S. mansoni lines: a praziquantel-resistant isolate (R), a praziquantel-susceptible isolate (S), and a co-infected line (RS), under three treatment regimens: untreated, 25 mg/kg praziquantel, or 50 mg/kg praziquantel. Life-history traits, including parasite adult-worm establishment, survival, reproduction (fecundity), and associated morbidity, were recorded in mice across all four generations. Predictor variables were tested in a series of generalized linear mixed effects models to determine which factors had a significant influence on parasite life-history traits in definitive hosts under different selection regimes.Praziquantel pressure significantly reduced adult-worm burdens across all generations and isolates, including within R-lines. However, previous drug treatment resulted in an increase in adult-worm establishment with increasing generation from P1 to F3. The highest worm numbers were in the co-infected RS line. Praziquantel treatment decreased adult-worm burden, but had a larger negative impact on the mean daily number of miracidia, a proxy for fecundity, across all three parasite isolates.Our predicted cost of resistance was not supported by the traits we measured within the murine host. We did not find evidence for negative adult worm density-dependent effects on fecundity. In contrast, of the adult worms that survived treatment, even low doses of praziquantel significantly reduced adult-worm fecundity. Such reductions in worm fecundity post treatment suggest that egg - based measures of drug efficacy, such as Kato-Katz, may overestimate the short-term effect of praziquantel on adult - worm burdens. These findings have important implications for S. mansoni transmission control, diagnostic protocols, and the potential for undetected selection toward drug resistance.

Dataset Information

Two-year longitudinal survey reveals high genetic diversity of Schistosoma mansoni with adult worms surviving praziquantel treatment at the start of mass drug administration in Uganda.

Publications

Two-year longitudinal survey reveals high genetic diversity of Schistosoma mansoni with adult worms surviving praziquantel treatment at the start of mass drug administration in Uganda.

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