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Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study.

ABSTRACT: 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.

SUBMITTER: Lamberton PHL

PROVIDER: S-EPMC5472905 | biostudies-literature | 2017 Jun

REPOSITORIES: biostudies-literature

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Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study.

Lamberton Poppy H L PHL Faust Christina L CL Webster Joanne P JP

Infectious diseases of poverty 20170616 1

<h4>Background</h4>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 th ...[more]

PMID: 28622767

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Project description:Natural selection acts on all organisms, including parasites, to maximize reproductive fitness. Drug resistance traits are often associated with life-history costs in the absence of treatment. Schistosomiasis control programmes rely on mass drug administration to reduce human morbidity and mortality. Although hotspots of reduced drug efficacy have been reported, resistance is not widespread. Using Bayesian state-space models (SSMs) fitted to data from an in vivo laboratory system, we tested the hypothesis that the spread of resistant Schistosoma mansoni may be limited by life-history costs not present in susceptible counterparts. S. mansoni parasites from a praziquantel-susceptible (S), a praziquantel-resistant (R) or a mixed line of originally resistant and susceptible parasites (RS) were exposed to a range of praziquantel doses. Parasite numbers at each life stage were quantified in their molluscan intermediate and murine definitive hosts across four generations, and SSMs were used to estimate key life-history parameters for each experimental group over time. Model outputs illustrated that parasite adult survival and fecundity in the murine host decreased across all lines, including R, with increasing drug pressure. Trade-offs between adult survival and fecundity were observed in all untreated lines, and these remained strong in S with praziquantel pressure. In contrast, trade-offs between adult survival and fecundity were lost under praziquantel pressure in R. As expected, parasite life-history traits within the molluscan host were complex, but trade-offs were demonstrated between parasite establishment and cercarial output. The observed trade-offs between generations within hosts, which were modified by praziquantel treatment in the R line, could limit the spread of R parasites under praziquantel pressure. Whilst such complex life-history costs may be difficult to detect using standard empirical methods, we demonstrate that SSMs provide robust estimates of life-history parameters, aiding our understanding of costs and trade-offs of resistant parasites within this system and beyond.

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.

Dataset Information

Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study.

Publications

Praziquantel decreases fecundity in Schistosoma mansoni adult worms that survive treatment: evidence from a laboratory life-history trade-offs selection study.

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