Soil-transmitted helminth reinfection four and six months after mass drug administration: results from the delta region of Myanmar.

Authors:
Julia C Dunn
Julia C Dunn
London Centre for Neglected Tropical Disease Research
London | United Kingdom
Alison A Bettis
Alison A Bettis
School of Public Health
Nay Yee Wyine
Nay Yee Wyine
London Centre for Neglected Tropical Disease Research
United Kingdom
Aung Tun
Aung Tun
Mahidol University
Thailand
Roy M Anderson
Roy M Anderson
Imperial College London
United Kingdom

PLoS Negl Trop Dis 2019 02 15;13(2):e0006591. Epub 2019 Feb 15.

Department of Infectious Disease Epidemiology, School of Public Health, Faculty of Medicine, Imperial College London, London, United Kingdom.

Background: 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 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 Findings: In 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/significance: 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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Source
http://dx.doi.org/10.1371/journal.pntd.0006591DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6395004PMC
February 2019
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References

(Supplied by CrossRef)
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Helminth control in school-age children
2012
Investigating the effectiveness of current and modified World Health Organization guidelines for the control of soil-transmitted helminth infections
SH Farrell et al.
Clin Infect Dis 2018
Differential effect of mass deworming and targeted deworming for soil-transmitted helminth control in children: a systematic review and meta-analysis
NE Clarke et al.
Lancet 2016

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