Impact of five annual rounds of mass drug administration with ivermectin on onchocerciasis in Sierra Leone

Background:Onchocerciasis is endemic in 12 of the 14 health districts of Sierra Leone.Good treatment coverage of community-directed treatment with ivermectin was achieved between 2005 and 2009 after the 11-year civil conflict.Sentinel site surveys were conducted in 2010 to evaluate the impact of five annual rounds of ivermectin distribution.Methods:In total,39 sentinel villages from hyper-and meso-endemic areas across the 12 endemic districts were surveyed using skin snips in 2010.Results were analyzed and compared with the baseline data from the same 39 villages.Results:The average microfilaridermia(MF)prevalence across 39 sentinel villages was 53.10%at baseline.The MF prevalence was higher in older age groups,with the lowest in the age group of 1-9 years(11.00%)and the highest in the age group of 40-49 years(82.31%).Overall mean MF density among the positives was 28.87 microfilariae(mf)/snip,increasing with age with the lowest in the age group of 1-9 years and the highest in the age group of 40-49 years.Males had higher MF prevalence and density than females.In 2010 after five rounds of mass drug administration,the overall MF prevalence decreased by 60.26%from 53.10%to 21.10%;the overall mean MF density among the positives decreased by 71.29%from 28.87 mf/snip to 8.29 mf/snip;and the overall mean MF density among all persons examined decreased by 88.58%from 15.33 mf/snip to 1.75 mf/snip.Ten of 12 endemic districts had>50%reduction in MF prevalence.Eleven of 12 districts had≥50%reduction in mean MF density among the positives.Conclusions:A significant reduction of onchocerciasis MF prevalence and mean density was recorded in all 12 districts of Sierra Leone after five annual MDAs with effective treatment coverage.The results suggested that the onchocerciasis elimination programme in Sierra Leone was on course to reach the objective of eliminating onchocerciasis in the country by the year 2025.Annual MDA with ivermectin should continue in all 12 districts and further evaluations are needed across the country to assist the NTDP with programme decision making.

Soil-transmitted helminth infection in school age children in Sierra Leone after a decade of preventive chemotherapy interventions

Background:Baseline mapping of soil-transmitted helminth(STH)infections among school age children(SAC)in 2008-2009 found high or moderate prevalence in 13 of the 14 districts in Sierra Leone.Following these surveys,mass drug administration(MDA)of mebendazole/albendazole was conducted biannually at national level targeting pre-school children(PSC)aged 12-59 months and intermittently at sub-national level targeting SAC.In addition,MDA with ivermectin and albendazole for eliminating lymphatic filariasis(LF)has been conducted nationwide since 2010 targeting individuals over 5 years of age.Each MDA achieved high coverage,except in 2014 when all but one round of MDA for PSC was cancelled due to the Ebola emergency.The objective of the current study was to determine the prevalence and intensity of STH infections among SAC after a decade of these deworming campaigns.Methods:Seventy-three schools in 14 districts were purposefully selected,including 39 schools from the baseline surveys,with approximately two sites from each of low,moderate and high prevalence categories at baseline per district.Fresh stool samples were collected from 3632 children aged 9-14 years(male 51%,female 49%)and examined using the Kato Katz technique.Results:The prevalence of STH infections in Sierra Leone decreased in 2016 compared to 2008:Ascaris lumbricoides 4.4%(95%confidence interval[CI]:3.7-5.1%)versus 6.6%(95%CI:0-25%),Trichuris trichiura 0.7%(95%CI:0.5-1.1%)versus 1.8%(95%CI:0-30.2%),hookworm 14.9%(95%CI:13.8-16.1)versus 38.5%(95%CI:5.4-95.1%),and any STH 18.3%(95%CI:17.0-19.5%)versus 48.3%(CI:5.4-96.3%),respectively.In 2016,no district had high hookworm prevalence and four districts had moderate prevalence,compared with eight and four districts respectively in 2008.In 2016,the arithmetic mean hookworm egg count in all children examined was light:45.5 eggs per gram(EPG)of faeces,(95%CI:\35.96-55.07 EPG);three(0.08%)children had heavy infections and nine(0.25%)children had moderate infections.Conclusions:Sierra Leone has made considerable progress toward controlling STH as a public health problem among SAC.As LF MDA phases out(between 2017 and 2021),transition of deworming to other platforms and water and sanitation strategies need to be strengthened to maintain STH control and ultimately interrupt transmission.