Achievements of the deworming programme in Sri Lanka
Authors: Antonio Montresor, Deniose Mupfasoni
Journal: The Lancet Global Health (2019)

In The Lancet Global Health, Dileepa Ediriweera and colleagues1Ediriweera DS Gunawardena S Gunawardena NK et al.Reassessment of the prevalence of soil-transmitted helminth infections in Sri Lanka to enable a more focused control programme: a cross-sectional national school survey with spatial modelling.Lancet Glob Health. 2019; (published online July 19.)http://dx.doi.org/10.1016/S2214-109X(19)30253-0Summary Full Text Full Text PDF PubMed Scopus (10) Google Scholar report the findings of the soil-transmitted helminth infection survey done in 2017, in Sri Lanka. The authors covered all nine provinces of Sri Lanka and populations known to be at high-risk of soil-transmitted helminth infections. The study population consisted of children aged 5–7 years attending state schools. The approach that the authors used to estimate the prevalence of soil-transmitted helminth infections in different areas of the country included a spatial modelling component: the parasitological data collected during the survey were analysed accounting for socio-demographic information (population density, education, type of household, type of sanitation equipment, and so on) and environmental variables (elevation, mean temperature, rain, and so on). This ingenious approach has allowed Ediriweera and colleagues to reduce the amount of parasitological data needed to properly assess the epidemiological situation and, therefore, to decrease the cost of the survey. From the data presented, the large-scale periodic distribution of anthelmintic treatment evidently was a successful exercise. The national prevalence of soil-transmitted helminth infection was 0·97% (95% CI 0·63–1·48) among primary schoolchildren, and most infections detected were of light intensity (60 [78%] of 77). These findings suggest that morbidity due to these infections has almost disappeared from Sri Lanka. However, these low prevalences were not homogeneously distributed across the country: in urban slums and tea plantation areas, where hygiene conditions are substantially worse, soil-transmitted helminth infection prevalence was 3 to 10 times higher than in the rest of the country (2·73%, 95% CI 0·75–6·87 in urban slum communities and 9·02%, 4·29–18·0 in plantation sector communities). This varied epidemiological situation is common in countries implementing preventive chemotherapy and calls for a geographical adaptation and adjustment of the control measures: Ediriweera and colleagues suggest that, in areas where prevalence is near zero (ie, in most of the country), the distribution of anthelmintic treatment could be suspended and some surveillance maintained to identify possible early recrudescence of infection, whereas in high-risk areas, preventive chemotherapy should be maintained, even if with a reduced frequency of treatment. The improvement of sanitation conditions in Sri Lanka during the past decade has also been very substantial: from 85% access to sanitation in 2000, the country reached over 99% sanitation coverage in 2017, in both urban and rural areas.2UNICEFUNICEF Data: monitoring the situation of children and women—Sanitation.https://data.unicef.org/topic/water-and-sanitation/sanitation/Date: 2019Date accessed: June 30, 2019Google Scholar This excellent level of sanitation, the highest in southeast Asia, strongly supports the expectation that the soil-transmitted helminth infection prevalence measured in the 2017 survey might remain low after the interruption of preventive chemotherapy interventions. The experience in Sri Lanka is particularly important because the country has been among the pioneers of mass treatment with anthelmintic medicines for the public health control of soil-transmitted helminth infections. This intervention, labelled by WHO as preventive chemotherapy,3Gabrielli A Montresor A Engels D Savioli L Preventive chemotherapy in human helminthiasis: theoretical and operational aspects.Trans R Soc Trop Med Hyg. 2011; 105: 683-693Summary Full Text Full Text PDF PubMed Scopus (97) Google Scholar was progressively scaled up worldwide during the past 10 years to reach, in 2017, more than 598 million children of preschool and school age, corresponding to almost 70% of those living in areas where soil-transmitted helminth infections are endemic.4Department of Control of Neglected Tropical DiseasesSchistosomiasis and soil-transmitted helminthiases: numbers of people treated in 2017.Wkly Epidemiol Rec. 2018; 93: 681-692Google Scholar This scaling up of the intervention has resulted in a substantial effect on associated morbidity.5Marocco C Bangert M Joseph SA Fitzpatrick C Montresor A Preventive chemotherapy in one year reduces by over 80% the number of individuals with soil-transmitted helminthiases causing morbidity: results from meta-analysis.Trans R Soc Trop Med Hyg. 2017; 111: 11-17Google Scholar, 6Montresor A Trouleau W Mupfasoni D et al.Preventive chemotherapy to control of soil transmitted helminthiasis averted more than 500 thousand DALYs in 2015.Trans R Soc Trop Med Hyg. 2017; 111: 457-463Crossref PubMed Scopus (29) Google Scholar The managers of the control programme in Sri Lanka faced challenges that other countries are expected to confront as they progress in their disease control efforts. Therefore, the experience of Sri Lanka is interesting and informative. The suspension and reduced frequency of preventive chemotherapy in response to the changing epidemiological situation also entails a decrease in the need for anthelmintic medicine and financial resources, representing an opportunity to refocus and maximise interventions in the remaining areas of marginalisation and poverty. WHO anticipates that between now and 2030, many of the control programmes that are in their initial phase will enter a more mature stage, and these programmes will achieve elimination of morbidity of soil-transmitted helminth infections. Such an accomplishment will also enable several endemic countries to reduce their dependence on drug donations and external aid for programme implementation. We declare no competing interests. Reassessment of the prevalence of soil-transmitted helminth infections in Sri Lanka to enable a more focused control programme: a cross-sectional national school survey with spatial modellingOur survey findings indicate that the national prevalence of soil-transmitted helminth infection has continued to decline in Sri Lanka. On the basis of WHO guidelines, we recommend discontinuation of routine deworming in low-risk areas, continuation of annual deworming in high-risk areas, and deworming once every 2 years in intermediate-risk areas, for at least 4 years. Full-Text PDF Open Access