The future of onchocerciasis control in Africa.
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ABSTRACT:
SUBMITTER: Hodgkin C
PROVIDER: S-EPMC2041822 | biostudies-literature | 2007 Oct
REPOSITORIES: biostudies-literature
Publications
The future of onchocerciasis control in Africa.
Hodgkin Catherine C Molyneux David H DH Abiose Adenike A Philippon Bernhard B Reich Michael R MR Remme J Hans JH Thylefors Bjorn B Traore Mamadou M Grepin Karen K
PLoS neglected tropical diseases 20071031 1
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Project description: Not available
| S-EPMC4310604 | biostudies-literature
Project description:BACKGROUND:A high prevalence and incidence of epilepsy has been reported in onchocerciasis-endemic regions in Central and East Africa. There is compelling epidemiological evidence suggesting that this high burden is caused by onchocerciasis-associated epilepsy (OAE). We hypothesized that OAE had also occured in West African onchocerciasis foci. METHODS:We searched PubMed, the African Journals Online platform and grey literature for population-based epilepsy studies in West African countries. Epilepsy and onchocerciasis prevalence data were extracted. The pre-control onchocerciasis endemicity in the study sites was estimated from historical data of onchocerciasis control programmes. The prevalence of epilepsy in different sites was analysed, taking into account onchocerciasis endemicity and the duration of control. RESULTS:The pooled prevalence of epilepsy in the West African study sites was 13.14 per 1000 (95% confidence interval 11.28-15.00). Higher pre-control endemicity and a shorter duration of onchocerciasis control were both associated with increased epilepsy prevalence (p<0.001). Two studies in Ivory Coast that provided detailed descriptions of persons with epilepsy in onchocerciasis-endemic settings revealed that most of them had features of OAE (73.7% and 83.3%, respectively). CONCLUSIONS:Our findings suggest that before and during the early years of implementing onchocerciasis control in West Africa, high onchocerciasis endemicity resulted in a high prevalence of OAE and that subsequent control efforts significantly reduced the prevalence of OAE.
| S-EPMC7320426 | biostudies-literature
Project description:This paper reviews the current management of onchocerciasis and its future prospects. Onchocerciasis is a disease affecting millions of people in Africa, South and Central America, and Yemen. It is spread by the blackfly as a vector and caused by the filarial nematode, Onchocerca volvulus. A serious attempt was made by the Onchocerciasis Control Program between 1975 and 2002 to eliminate the vector in eleven of the endemic countries in West Africa, and with remarkable success. Formerly, the treatment was with diethyl carbamazine for the microfilaria and suramin for the adult worm. These drugs are now known to be toxic and unsuitable for mass distribution. In particular, they precipitate optic nerve disease. With the discovery of ivermectin, a much safer microfilaricide, and the decision of Merck to distribute the drug free of charge for as long as needed, the strategy of control switched to mass drug administration through community-directed treatment with ivermectin. So far, millions have received this annual or biannual treatment through the African Program for Onchocerciasis Control and the Onchocerciasis Elimination Program for the Americas. However, the problem with ivermectin is that it is a monotherapy microfilaricide which has limited effect on the adult worm, and thus will need to be continued for the life span of the adult worm, which may last up to 15 years. There are also early reports of resistance. Serious encephalopathy and death may occur when ivermectin is used in subjects heavily infested with loiasis. It seems unlikely that a break in transmission will occur with community-directed treatment with ivermectin in Africa because of population migrations and the highly efficient vector, but in the Americas some countries such as Columbia and the Oaxaca focus in Mexico have reported eradication. Vector control is only now applicable in selected situations, and particularly to control the nuisance value of the blackfly. Trials are ongoing for alternatives to ivermectin. Candidate drugs include moxidectin, a macrofilaricide, doxycycline which targets the Wolbachia endosymbiont, and flubendazole, which shows promise with the newer oral cyclodextrin formulation.
| S-EPMC3206119 | biostudies-other
Project description:BACKGROUND:Onchocerciasis transmission across international borders is not uncommon, yet a coordinated cross border stops mass drug administration (MDA) decision has not been documented. METHODS/PRINCIPLE FINDINGS:The Galabat-Metema focus involves neighboring districts on the border between Sudan and Ethiopia. Mass drug administration (MDA) was provided once and subsequently twice per year in this focus, with twice-per-year beginning in Ethiopia's Metema subfocus in 2016 and in the Sudan's Galabat subfocus in 2008. Ov16 ELISA-based serosurveys were conducted in 6072 children under 10 years of age in the Metema subfocus in 2014, and 3931 in the Galabat in 2015. Between 2014 and 2016, a total of 27,583 vector Simulium damnosum flies from Metema and 9,148 flies from Galabat were tested by pool screen PCR for Onchocerca volvulus O-150 DNA. Only 8 children were Ov16 seropositive (all in the Metema subfocus); all were negative by skin snip PCR. The upper limit of the 95% confidence interval (UCL) for Ov16 seropositive was <0.1% for the overall focus and 0.14 positive fly heads per 2000 (UCL = 0.39/2000). However, an entomological 'hotspot' was detected on the Wudi Gemzu river in Metema district. The hotspot was confirmed when 4 more positive fly pools were found on repeat testing in 2017 (1.04 L3/2000 flies (UCL = 2.26/2000). Information exchange between the two countries led to stopping MDA in a coordinated fashion in 2018, with the exception of the hotspot at Wudi Gemzu, where MDA with ivermectin was increased to every three months to hasten interruption of transmission. CONCLUSION:Coordinated stop MDA decisions were made by Sudan and Ethiopia based on data satisfying the World Health Organization's criteria for interruption of onchocerciasis transmission. Definitions of entomological 'hotspots' and buffer zones around the focus are proposed.
| S-EPMC7004312 | biostudies-literature
Project description:BackgroundThe control of onchocerciasis in Ghana started in 1974 under the auspices of the Onchocerciasis Control Programme (OCP). Between 1974 and 2002, a combination of approaches including vector control, mobile community ivermectin treatment, and community-directed treatment with ivermectin (CDTI) were employed. From 1997, CDTI became the main control strategy employed by the Ghana OCP (GOCP). This review was undertaken to assess the impact of the control interventions on onchocerciasis in Ghana between 1974 and 2016, since which time the focus has changed from control to elimination.MethodsIn this paper, we review programme data from 1974 to 2016 to assess the impact of control activities on prevalence indicators of onchocerciasis. This review includes an evaluation of CDTI implementation, microfilaria (Mf) prevalence assessments and rapid epidemiological mapping of onchocerciasis results.ResultsThis review indicates that the control of onchocerciasis in Ghana has been very successful, with a significant decrease in the prevalence of infection from 69.13% [95% confidence interval) CI 60.24-78.01] in 1975 to 0.72% (95% CI 0.19-1.26) in 2015. Similarly, the mean community Mf load decreased from 14.48 MF/skin snip in 1975 to 0.07 MF/skin snip (95% CI 0.00-0.19) in 2015. Between 1997 and 2016, the therapeutic coverage increased from 58.50 to 83.80%, with nearly 100 million ivermectin tablets distributed.ConclusionsDespite the significant reduction in the prevalence of onchocerciasis in Ghana, there are still communities with MF prevalence above 1%. As the focus of the GOCP has changed from the control of onchocerciasis to its elimination, both guidance and financial support are required to ensure that the latter goal is met.
| S-EPMC7778817 | biostudies-literature
Project description:BackgroundOnchocerciasis is found predominantly in Africa where large scale vector control started in 1974. Registration and donation of ivermectin by Merck & Co in 1987 enabled mass treatment with ivermectin in all endemic countries in Africa and the Americas. Although elimination of onchocerciasis with ivermectin was considered feasible only in the Americas, recently it has been shown possible in Africa too, necessitating fundamental changes in technical and operational approaches and procedures.Main bodyThe American programme(OEPA) operating in onchocerciasis epidemiological settings similar to the mild end of the complex epidemiology of onchocerciasis in Africa, has succeeded in eliminating onchocerciasis from 4 of its 6 endemic countries. This was achieved through biannual mass treatment with ivermectin of 85% of the eligible population, and monitoring and evaluation using serological tests in children and entomological tests. The first African programme(OCP) had a head start of nearly two decades. It employed vector control and accumulated lots of knowledge on the dynamics of onchocerciasis elimination over a wide range of epidemiological settings in the vast expanse of its core area. OCP made extensive use of modelling and operationalised elimination indicators for entomological evaluation and epidemiological evaluation using skin snip procedures. The successor African programme(APOC) employed mainly ivermectin treatment. Initially its objective was to control onchocerciasis as a public health problem but that objective was later expanded to include the elimination of onchocerciasis where feasible. Building on the experience with onchocerciasis elimination of the OCP, APOC has leveraged OCP's vast modelling experience and has developed operational procedures and indicators for evaluating progress towards elimination and stopping ivermectin mass treatment of onchocerciasis in the complex African setting.ConclusionsFollowing the closure of APOC in 2015, implementation of onchocerciasis elimination in Africa appears to overlook all the experience that has been accumulated by the African programmes. It is employing predominantly American processes that were developed in a dissimilar setting from the complex African onchocerciasis setting. This is impeding progress towards decisions to stop intervention in many areas that have reached the elimination point. This article summarizes lessons learned in Africa and their importance for achieving elimination in Africa by 2025.
| S-EPMC6029117 | biostudies-literature
Project description:Onchocerciasis is a parasitic, vector borne disease caused by the filarial nematode Onchocerca volvulus. More than 99% of the population at risk of infection live in Africa. Onchocerciasis control was initiated in West Africa in 1974 with vector control, later complemented by ivermectin mass drug administration and in the other African endemic countries in 1995 with annual community directed treatment with ivermectin (CDTI.) This has significantly reduced infection prevalence. Together with proof-of-concept for onchocerciasis elimination with annual CDTI from foci in Senegal and Mali, this has resulted in targeting onchocerciasis elimination in selected African countries by 2020 and in 80% of African countries by 2025. The challenges for meeting these targets include the number of endemic countries where conflict has delayed or interrupted control programmes, cross-border foci, potential emergence of parasite strains with low susceptibility to ivermectin and co-endemicity of loiasis, another parasitic vector borne disease, which slows down or prohibits CDTI implementation. Some of these challenges could be addressed with new drugs or drug combinations with a higher effect on Onchocerca volvulus than ivermectin. This paper reviews the path from discovery of new compounds to their qualification for large scale use and the support regulatory authorities provide for development of drugs for neglected tropical diseases. The status of research for new drugs or treatment regimens for onchocerciasis along the path to regulatory approval and qualification for large scale use is reviewed. This research includes new regimens and combinations of ivermectin and albendazole, antibiotics targeting the O. volvulus endosymbiont Wolbachia, flubendazole, moxidectin and emodepside and discovery of new compounds.
| S-EPMC5196484 | biostudies-literature
Project description:BackgroundGreat strides have been made toward onchocerciasis elimination by mass drug administration (MDA) of ivermectin. Focusing on MDA-eligible areas, we investigated where the elimination goal can be achieved by 2025 by continuation of current practice (annual MDA with ivermectin) and where intensification or additional vector control is required. We did not consider areas hypoendemic for onchocerciasis with loiasis coendemicity where MDA is contraindicated.MethodsWe used 2 previously published mathematical models, ONCHOSIM and EPIONCHO, to simulate future trends in microfilarial prevalence for 80 different settings (defined by precontrol endemicity and past MDA frequency and coverage) under different future treatment scenarios (annual, biannual, or quarterly MDA with different treatment coverage through 2025, with or without vector control strategies), assessing for each strategy whether it eventually leads to elimination.ResultsAreas with 40%-50% precontrol microfilarial prevalence and ≥10 years of annual MDA may achieve elimination with a further 7 years of annual MDA, if not achieved already, according to both models. For most areas with 70%-80% precontrol prevalence, ONCHOSIM predicts that either annual or biannual MDA is sufficient to achieve elimination by 2025, whereas EPIONCHO predicts that elimination will not be achieved even with complementary vector control.ConclusionsWhether elimination will be reached by 2025 depends on precontrol endemicity, control history, and strategies chosen from now until 2025. Biannual or quarterly MDA will accelerate progress toward elimination but cannot guarantee it by 2025 in high-endemicity areas. Long-term concomitant MDA and vector control for high-endemicity areas might be useful.
| S-EPMC5982715 | biostudies-literature
Project description:BackgroundOnchocerciasis, or river blindness, is one of the neglected tropical diseases (NTDs) that the WHO has set out to eliminate. To reach this elimination target, a number of challenges must be met, and the essential measures set out in the road map for NTDs 2021-2030 must be implemented. More than 99% of infected people live in 31 countries in sub-Saharan Africa. Our objective was to assess the impact of onchocerciasis interventions in Africa.MethodologyA systematic peer review of the existing literature following the PRISMA guidelines was performed between November 2021 and April 2022. We selected studies on onchocerciasis control measures in Africa since the implementation of the first Onchocerciasis Control Programme (OCP) measures in 1974. All scientific articles indexed in the PubMed, Scopus, Embase, and CENTRAL databases written in Spanish, English, French, German, and Portuguese were considered. The study protocol was registered in the PROSPERO database.ResultsA total of 63 articles met the inclusion criteria and were finally selected. Publications were found from 19 out of 31 African endemic countries. The main intervention retained in the different published studies was mass distribution of ivermectin (n = 51). According to our results, 11 African countries have managed to interrupt transmission of onchocerciasis in at least one area in the country; 11 countries have not achieved this goal, while 1 country has managed to eliminate the disease, but it has resurged.ConclusionsControl interventions showed a positive impact on the fight against onchocerciasis, demonstrating that these activities are effective. Nevertheless, they were not sufficient to achieve the proposed goals for a variety of reasons. Therefore, different aspects should be considered in order to fulfil the targets proposed by the WHO to be reached in 2030.
| S-EPMC11768683 | biostudies-literature
Project description:BackgroundBy 1987, onchocerciasis in Niger had been successfully controlled in the six endemic river basins. In 2017, onchocerciasis elimination mapping (OEM) was carried out to determine if there was any ongoing transmission in the country as a whole.MethodsThe recommended OEM procedures were implemented.ResultsTen districts, that included 35 villages, required field investigation as sites of possible transmission. None of these were found capable of supporting black fly breeding, nor was there any evidence of the presence of Simulium sp. flies.ConclusionsThe implementation of OEM indicates that there is no transmission of onchocerciasis currently taking place in these newly assessed sites in Niger.
| S-EPMC10911525 | biostudies-literature