Progress in controlling the reinvasion of wind borne vectors into the western area of the Onchocerciasis Control Programme in West Africa

Baker, Robert Horace; Guillet, P.; Sékétéli, A.; Poudiougo, P.; Boakye, D.; Wilson, M. D.; Bissan, Y.

doi:10.4000/books.irdeditions.28674

Cited by 8 publications

(8 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Several factors may have contributed to the differences in the impact of CDTi. Among these include variations in program implementation in the areas (variation in treatment coverage [34,58,63,64]; treatment non-compliance rate [48,61,63,65]; differences in vector species [50,64], densities [55,56,60,62,63,65], biting rates [64], vectorial capacities [64], vector competences [50,64,66,67], vector migration [68][69][70][71]; ecological conditions [58,59,64,72]; transmission pattern [50]; parasite susceptibility to ivermectin [73,74]; human migration [64,65], and difference in time after community-wide treatment and parasitological assessment). Another possible explanation is that variation in pre-control endemicity level could influence the long term impact of ivermectin on prevalence of infection [34,50,51,57,64,75,76].…”

Section: Discussionmentioning

confidence: 99%

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

et al. 2020

View full text Add to dashboard Cite

Background: Control and elimination of onchocerciasis requires regular follow-up and evaluation of community directed treatment with ivermectin (CDTi) program implementation. This research was aimed to assess the epidemiological status of onchocerciasis in disease endemic communities of Asosa and Yeki districts of Ethiopia after 5 and 15 years of successive CDTi respectively, and to evaluate the decline in infection and morbidity burden. Methods: A community-based cross-sectional study was conducted from August 2017 to January 2018 (i.e. within 2-7 months since the last treatment) using interview, physical and parasitological examinations. Pre-CDTi epidemiological data were obtained from studies conducted prior to the launch of CDTi. Results: A total of 3002 individuals (1567 from Asosa and 1435 from Yeki) were included. No infection was detected from Yeki. In Asosa, the prevalence of infection was 1.6%. The geometric mean intensity of infection was 0.02 mf/mg of skin snip. The prevalence rates of dermatitis, depigmentation, nodule, and atrophy in Yeki were 33(2.3%), 57(4%), 37(2.6%) and 11(0.7%), respectively. The prevalence rates of papular dermatitis, depigmentation, palpable nodule, atrophy, and blindness in Asosa were 94(6%), 38(2.4%), 30(1.9%), 28(1.8%) and 2(0.1%), respectively. Five years of CDTi had significantly reduced prevalence and intensity of infection by 91.8% (p < 0.001) and 99.7% (p < 0.001), respectively. Moreover, CDTi reduced prevalence of papular dermatitis by 95.9% (p < 0.001), palpable nodule by 90.5% (p < 0.001), and atrophy by 30% (p = 0.6) in Yeki. Similarly, CDTi reduced prevalence of papular dermatitis by 88.6% (p < 0.001), depigmentation by 90.3% (p < 0.001), atrophy by 89.5% (p < 0.001), and blindness by 90% (p < 0.001) in Asosa.

show abstract

Section: Discussionmentioning

confidence: 99%

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

et al. 2020

View full text Add to dashboard Cite

show abstract

“…This has implications for defining so called “transmission zones” when planning and implementing elimination programs. Previous studies have suggested that the savanna dwelling species of Simulium damnosum can travel long distances in West Africa, migrating on seasonal winds [ 30 ]. This suggests that transmission zones may be quite large, on the order of hundreds of kilometers in diameter.…”

Section: Discussionmentioning

confidence: 99%

Community-directed vector control to supplement mass drug distribution for onchocerciasis elimination in the Madi mid-North focus of Northern Uganda

et al. 2018

View full text Add to dashboard Cite

BackgroundOnchocerciasis a neglected tropical disease that historically has been a major cause of morbidity and an obstacle to economic development in the developing world. It is caused by infection with Onchocerca volvulus, which is transmitted by black flies of the genus Simulium. The discovery of the potent effect of Mectizan (ivermectin) on O. volvulus microfilariae and the decision by its manufacturer to donate the drug for onchocerciasis spurred the implementation of international programs to control and, more recently, eliminate this scourge. These programs rely primarily on mass distribution of ivermectin (MDA) to the afflicted populations. However, MDA alone will not be sufficient to eliminate onchocerciasis where transmission is intense and where ivermectin MDA is precluded by co-endemicity with Loa loa. Vector control will likely be required as a supplemental intervention in these situations.Methodology/Principal findingsBecause biting by the black fly vectors is often a major nuisance in onchocerciasis afflicted communities, we hypothesized that community members might be mobilized to clear the breeding sites of the vegetation that represents the primary black fly larvae attachment point. We evaluated the effect of such a community based "slash and clear" intervention in multiple communities in Northern Uganda. Slash and Clear resulted in 89–99% declines in vector biting rates. The effect lasted up to 120 days post intervention.Conclusions/SignificanceSlash and clear might represent an effective, inexpensive, community- based tool to supplement ivermectin distribution as a contributory method to eliminate onchocerciasis and prevent recrudescence.

show abstract

“…If that is the case and if CDTI selects for SOR, this selection in the Pru, Daka and Black Volta/Tombe river basins could be reflected in the parasite population in our study participants. Long range transmission of parasites through infected/infective vector movement was a challenge for the Onchocerciasis Control Programme in West Africa, resulting in extensions of the original programme area [56][57][58][59]. Recently long range vector movement has been implicated in renewed transmission of O. volvulus in the Comoé valley of Burkina Faso, although movement of infected people could not be excluded [60,61].…”

Section: Discussionmentioning

confidence: 99%

Effect of a single dose of 8 mg moxidectin or 150 µg/kg ivermectin on O. volvulus skin microfilariae in a randomized trial: Differences between areas in the Democratic Republic of the Congo, Liberia and Ghana and impact of intensity of infection

Bakajika

Kanza

Opoku³

et al. 2022

Preprint

View full text Add to dashboard Cite

Background Community-directed treatment with 150 μg/kg ivermectin (CDTI), the current control strategy, is insufficient for eliminating Onchocerca volvulus transmission across sub-Saharan Africa. Our study in CDTI-naïve areas in Nord Kivu and Ituri (Democratic Republic of the Congo (DRC), Lofa County (Liberia) and Nkwanta district (Ghana) showed that a single 8 mg moxidectin dose reduced skin microfilariae density (microfilariae/mg skin, SmfD) better and for longer than a single 150μg/kg ivermectin dose. Methodology/Principal Findings We analysed drug efficacy by study area and pre-treatment SmfD (intensity of infection, IoI). Four and three IoI categories were defined for across-study and by-study area analyses, respectively. We used a general linear model to analyse SmfD 1, 6, 12 and 18 months post-treatment, a logistic model to determine the odds of undetectable SmfD from month 1 to month 6 (UD1-6), month 12 (UD1-12) and month 18 (UD1-18), and descriptive statistics to quantitate inter-interindividual response differences. Twelve months post-treatment, treatment differences were 92.9%, 90.1%, 86.8% and 84.5% in Nord Kivu, Ituri, Lofa and Nkwanta, and 74.1%, 84.2%, 90.0% and 95.4% for participants with SmfD 10-20, ≥20<50, ≥50-<80, ≥80, respectively. Ivermectin's efficacy was lower in Ituri and Nkwanta than Nord Kivu and Lofa (p≤0.002) and moxidectin's efficacy lower in Nkwanta than Nord Kivu, Ituri and Lofa (p<0.006). Odds ratios for UD1-6, UD1-12 or UD1-18 after moxidectin versus ivermectin treatment exceeded 7.0. Suboptimal response (SmfD 12 months post-treatment >40% of pretreatment SmfD) occurred in 0%, 0.3%, 1.6% and 3.9% of moxidectin and 12.1%, 23.7%, 10.8% and 28.0% of ivermectin treated participants in Nord Kivu, Ituri, Lofa and Nkwanta, respectively. Conclusions/significance The benefit of moxidectin vs ivermectin treatment increased with pre-treatment IoI. The possibility that parasite populations in different areas have different drug susceptibility without prior ivermectin selection pressure needs to be considered and further investigated.

show abstract

Progress in controlling the reinvasion of wind borne vectors into the western area of the Onchocerciasis Control Programme in West Africa

Cited by 8 publications

References 11 publications

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

Status of parasitological indicators and morbidity burden of onchocerciasis after years of successive implementation of mass distribution of ivermectin in selected communities of Yeki and Asosa districts, Ethiopia

Community-directed vector control to supplement mass drug distribution for onchocerciasis elimination in the Madi mid-North focus of Northern Uganda

Effect of a single dose of 8 mg moxidectin or 150 µg/kg ivermectin on O. volvulus skin microfilariae in a randomized trial: Differences between areas in the Democratic Republic of the Congo, Liberia and Ghana and impact of intensity of infection

Contact Info

Product

Resources

About