Trends in Parasitology
ReviewInterpreting low praziquantel cure rates of Schistosoma mansoni infections in Senegal
Section snippets
Selecting PZQ population studies
All published S. mansoni population selective-treatment studies with the standard dose of 40 mg kg−1 of PZQ from a known brand have been collated here. For inclusion of a study, the outcome of treatment had to be expressed as a cure rate (i.e. proportion of treated cases that became negative for S. mansoni eggs at follow-up). Only studies with follow-up within 1 month and 1 year were included. Studies with previous PZQ treatment within two years or additional transmission control were excluded.
Meta-analysis
Different communities within a study and repeated follow-ups were each considered as separate data points. A cut-off sample size of >40 persons treated and followed-up was chosen to prevent unrealistic weightings. This led to the exclusion of ten villages (out of 44) from the study by Barakat et al. [31] and two from other studies 15, 26. Eventually, a total of 63 data points out of 48 communities were available for analysis.
The interdependence between observations (communities and repeated
Comparing cure rates
Other reports have suggested that the low S. mansoni cure rates in Senegal could be explained by the high initial intensities of infection, but they could not quantify this assumption 5, 6, 7, 13, 18. This study provides evidence following standardization and statistical comparison between various population studies that initial, high egg-counts explain part of the deviation of Senegal from average endemic settings. However, even after accounting for intensity of infection and follow-up time,
Conclusions
It has been demonstrated here quantitatively that the high pre-treatment levels of infection can partly explain the low cure rates consistently observed in a series of studies in Senegal. The relatively sensitive diagnosis in some of the studies led to a further, limited downward deviation of the observed cure rates. However, even after accounting for intensity of infection and sensitivity of diagnosis, Senegal remained atypical by showing cure rates significantly lower than expected. Although
Acknowledgements
This study would not have been possible without the efforts made by several authors who provided additional information on our request. In particular, we are grateful to Rashida Barakat, DeWolfe Miller, Jean-Christophe Ernould and Katja Polman for going back to their data to make alternative calculations. Alan Fenwick, Donato Cioli, Susan Watts, Foekje Stelma and Mike Doenhoff also provided essential information. We thank Caspar Looman, Gerard Borsboom and Nico Nagelkerke for statistical
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