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

Abstract

BackgroundOnchocerciasis 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.MethodsIn 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.ResultsThe 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.ConclusionsA 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.Electronic supplementary materialThe online version of this article (10.1186/s40249-018-0410-y) contains supplementary material, which is available to authorized users.

Update on the current status of onchocerciasis in Côte d’Ivoire following 40 years of intervention: Progress and challenges

“…Similar studies aimed to determine onchocerciasis MF prevalence and CMFL have been reported in Sierra Leone and Cameroon after repeated annual treatment with ivermectin [ 22 , 23 ]. Our findings are similar to those recently reported in Sierra Leone where skin MF prevalence were still between 10 and 30% after implementation of 5 continuous MDA rounds with ivermectin [ 24 ].…”

Progress on elimination of lymphatic filariasis in Sierra Leone

“…This significant reduction may have been partly due to the use of ivermectin for onchocerciasis control, as reported in some other countries [ 28 , 29 ]. In Sierra Leone, ivermectin was used pre-conflict in limited space in the country [ 30 ], but large scale use through CDTI did not start until 1995 as the Special Intervention Zone of the African Programme of Onchocerciasis Control, in meso- and hyper-endemic villages [ 13 ]. However, due to the civil conflict between 1991–2002, CDTI did not achieve satisfactory treatment coverage until 2005 and was expanded to accommodate district-wide LF MDA by adding albendazole in 2007–2008 [ 13 ].…”

“…In Sierra Leone, ivermectin was used pre-conflict in limited space in the country [ 30 ], but large scale use through CDTI did not start until 1995 as the Special Intervention Zone of the African Programme of Onchocerciasis Control, in meso- and hyper-endemic villages [ 13 ]. However, due to the civil conflict between 1991–2002, CDTI did not achieve satisfactory treatment coverage until 2005 and was expanded to accommodate district-wide LF MDA by adding albendazole in 2007–2008 [ 13 ]. Therefore, the prior ivermectin use in the 12 dsitricts may have contributed to the reduction of LF prevalence.…”

“…In 2005, the Ministry of Health and Sanitation in Sierra Leone conducted nationwide LF mapping with support from WHO and found that all 14 districts were endemic for LF while 12 rural districts (except Western Areas), were co-endemic with onchocerciasis [ 12 , 13 ]. The existing National Onchocerciasis Control Programme (NOCP) was expanded in 2007 to become the national integrated Neglected Tropical Disease Programme (NTDP) including LF, schistosomiasis and soil-transmitted helminthiasis [ 12 , 14 , 15 ].…”

Onchodermatitis: Where Are We Now?

“…In Sierra Leone, civil conflict also resulted in limited onchocerciasis control activities from 1991–2002, but after the war, good CDTi was achieved between 2005 and 2009. In 2010, after 5 rounds of ivermectin, 10 out of 12 endemic districts had a >50% reduction in mf prevalence and 11 of 12 districts had ≥50% reduction in mean mf density among the positives, suggesting that Sierra Leone will now be on course to achieve elimination by the year 2025 [ 90 ].…”