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Genetic Consequences of Mass Human Chemotherapy for Schistosoma mansoni: Population Structure Pre- and Post-Praziquantel Treatment in Tanzania

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  • Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine, London, United Kingdom; Department of Zoology, The Natural History Museum, London, United Kingdom; Mwanza Research Centre, National Institute for Medical Research, Mwanza, Tanzania

Recent shifts in global health policy have led to the implementation of mass drug administration (MDA) for neglected tropical diseases. Here we show how population genetic analyses can provide vital insights into the impact of such MDA on endemic parasite populations. We show that even a single round of MDA produced a genetic bottleneck with reductions in a range of measures of genetic diversity of Schistosoma mansoni. Phylogenetic analyses and indices of population differentiation indicated that schistosomes collected in the same schools in different years were more dissimilar than those from different schools collected within either of the study's 2 years, in addition to distinguishing re-infection from non-clearance (that might indicate putatively resistant parasites) from within those children infected at both baseline and follow-up. Such unique results illustrate the importance of genetic monitoring and examination of long lived multi-cellular parasites such as these under novel or increased chemotherapeutic selective pressures.

Author Notes

*Address correspondence to Joanne P. Webster, Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine, London, W2 1PG, United Kingdom. E-mail: joanne.webster@imperial.ac.uk

Financial support: Field work, analyses and/or authors were supported by grants from the Bill and Melinda Gates Foundation, the European Union (CONTRAST EU/INCO.Dev contract no.: 032203), the Wellcome Trust (grant number WT063774), and the Royal Society (JPW as a Royal Society University Research Fellow, Charlotte Gower as a Dorothy Hodgkin Fellow).

Authors' addresses: Alice J. Norton, Charlotte M. Gower, Poppy H. L. Lamberton, Lynsey Blair, Alan Fenwick, and Joanne P. Webster, Department of Infectious Disease Epidemiology, Imperial College, Faculty of Medicine, London, UK, E-mails: a.norton@wellcome.ac.uk, charlotte.gower@imperial.ac.uk, poppy.lamberton@imperial.ac.uk, lynsey.blair@imperial.ac.uk, alan.fenwick@imperial.ac.uk, and joanne.webster@imperial.ac.uk. Alice J. Norton current address: The Wellcome Trust, London, UK. Bonnie L. Webster, Department of Zoology, The Natural History Museum, London, UK, E-mail: b.webster@nhm.ac.uk. Nicholas J. S. Lwambo, Mwanza Research Centre, National Institute for Medical Research, Mwanza, Tanzania, E-mail: lwambon@live.co.uk.

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