Abstract

BackgroundMass drug administration (MDA), targeted at school-aged children (SAC) is the method recommended by the World Health Organization for the control of morbidity induced by soil-transmitted helminth (STH) infection in endemic countries. However, MDA does not prevent reinfection between treatment rounds and research suggests that only treating SAC will not be sufficient to bring prevalence to low levels and possibly interrupt transmission of STH. In countries with endemic infection, such as Myanmar, the coverage, who is targeted, and rates of reinfection will determine how effective MDA is in suppressing transmission in the long-term.Methods/principal findingsIn this paper, data from an epidemiological study on STH, comprising three surveys conducted between June 2015 and June 2016 in the delta region of Myanmar, are analysed to determine how STH prevalence and intensity in the study community changes over the course of a year, including reinfection after two MDA rounds in which the whole study sample (all age groups, n = 523) were treated with albendazole. Prevalence in the first survey (August 2015) was 27.92% for any STH, 5.54% for Ascaris lumbricoides, 17.02% for Trichuris trichiura and 9.75% for hookworm. Over the year (survey one to survey three), prevalence of any STH decreased by 8.99% (P < 0.001) and mean EPG significantly decreased for T. trichiura (P < 0.01) and hookworm (P < 0.001). Risk ratios (RRs) for a four-month reinfection period (August to December) were statistically significant and were below one, indicating that STH prevalence had not bounced back to the prevalence levels recorded immediately prior to the last round of treatment (any STH RR = 0.67, 95% CI 0.56–0.81; A. lumbricoides RR = 0.31, 95% CI 0.16–0.59; T. trichiura RR = 0.70, 95% CI 0.55–0.88; hookworm RR = 0.69, 95% CI 0.50–0.95). The only statistically significant RR for the six-month reinfection period (December to June) was for A. lumbricoides infection in SAC (RR = 2.67, 95% CI 1.37–5.21). All six-month RRs were significantly higher than four-month RRs (P < 0.05). Evidence of predisposition to infection (low and high), as measured by the Kendall Tau-b statistic, was found for all species overall and within most age groups stratifications, except for hookworm infection in preschool-aged children.Conclusions/significanceThis study demonstrates that, for certain demographic groups, a six-month gap between MDA in these communities is enough time for STH infection to return to STH prevalence levels recorded immediately before the previous MDA round, and that on average the same individuals are being consistently infected between MDA rounds.

Highlights

  • Soil-transmitted helminth infections (STHs) are classified by the World Health Organization (WHO) as neglected tropical diseases (NTDs)

  • Mass drug administration (MDA), targeted at school-aged children (SAC) is the method recommended by the World Health Organization for the control of morbidity induced by soiltransmitted helminth (STH) infection in endemic countries

  • This study demonstrates that, for certain demographic groups, a six-month gap between MDA in these communities is enough time for STH infection to return to STH prevalence levels recorded immediately before the previous MDA round, and that on average the same individuals are being consistently infected between MDA rounds

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Summary

Introduction

Soil-transmitted helminth infections (STHs) are classified by the World Health Organization (WHO) as neglected tropical diseases (NTDs). Endemic countries carry out mass drug administration (MDA) campaigns to control STH infections with the goals of reducing STH prevalence and intensity of infection to a level where there is a low risk of morbidity in children [2,3]. Whilst MDA that targets pre-SAC and SAC can reduce morbidity in these groups, research indicates that MDA targeting all age groups (community-wide) is more effective at reducing STH prevalence and intensity in all groups, especially in hookworm-endemic areas [5,6], and to interrupt transmission [7,8,9]. Mass drug administration (MDA), targeted at school-aged children (SAC) is the method recommended by the World Health Organization for the control of morbidity induced by soiltransmitted helminth (STH) infection in endemic countries. In countries with endemic infection, such as Myanmar, the coverage, who is targeted, and rates of reinfection will determine how effective MDA is in suppressing transmission in the long-term

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