Towards the Elimination of the Bioko Form of <i>Simulium Yahense</i> from Bioko: Planning and Insecticide Trials

Cheke, Robert; Meyer, Rolf; Barro, T; Mas, J.; Sima, A.; Abaga, Simón; Noma, Mounkaïla; Sékétéli, A.; Wilson, Michael D.

doi:10.2478/v10043-009-0013-8

Cited by 3 publications

(2 citation statements)

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“…A feasibility study was carried out in 1996, confirming the high vectorial efficiency of the endemic Bioko form of S imulium yahense [ 13 ] and the distribution of the vector breeding sites [ 14 ]. From 2001 to 2005, a large-scale larviciding trial using ground-based applications was undertaken using helicopter and ground-based applications of temephos [ 8 , 15 ]. In 2005, the endemic Bioko form of S .…”

Section: Introductionmentioning

confidence: 99%

Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea

et al. 2018

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BackgroundOnchocerciasis, also known as river blindness, is a parasitic disease. More than 99 percent of all cases occur in Africa. Bioko Island (Equatorial Guinea) is the only island endemic for onchocerciasis in the world. Since 2005, when vector Simulium yahense was eliminated, there have not been any reported cases of infection. This study aimed to demonstrate that updated WHO criteria for stopping mass drug administration (MDA) have been met.Methodology/Principal findingsA cross-sectional study was conducted from September 2016 to January 2017. Participants were 5- to 9-year-old school children. Onchocerciasis/lymphatic Filariasis (LF, only in endemic districts) rapid diagnostic tests (RDTs) were performed. Blood spots were collected from RDT positive children and 10 percent of the RDT negatives to determine Ov16 and Wb123 IgG4 antibodies through enzyme-linked immunosorbent assay (ELISA). Skin snips were collected from RDT positives. Filarial detection was performed by PCR in positives and indeterminate sera. Black fly collection was carried out in traditional breeding sites. A total of 7,052 children, ranging from 5 to 9 years of age, were included in the study. Four children (0.06%) were Ov16 IgG4 RDT positives, but negative by ELISA Ov16, while 6 RDT negative children tested positive by ELISA. A total of 1,230 children from the Riaba and Baney districts were tested for LF. One child was Wb123 RDT positive (0.08%), but ELISA negative, while 3 RDT negative children were positive by Wb123 ELISA. All positive samples were negative by PCR for onchocerciasis and LF (in blood spot and skin snip). All fly collections and larval prospections in the traditional catching and prospection sites were negative.Conclusions/SignificanceWHO criteria have been met, therefore MDA in Bioko Island can be stopped. Three years of post-treatment surveillance should be implemented to identify any new occurrences of exposure or infection.

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Section: Introductionmentioning

confidence: 99%

Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea

et al. 2018

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“…This dataset, recording weekly averages of DBRs during 2001 at three different sites (Musola, Barleycorn and Sampaca), was collected as part of APOC pilot studies on the effectiveness and feasibility of localized vector control in the elimination of onchocerciasis from Bioko, an island off the coast of Cameroon and part of Equatorial Guinea. Detailed collection methods were described in [ 29 ]. Bioko is covered by large swathes of forest, and the local onchocerciasis vectors (the Bioko form of S. yahense [ 30 ]) have now been eliminated from the island [ 31 ] (in addition to ivermectin MDA being implemented).…”

Section: Methodsmentioning

confidence: 99%

Modelling the impact of larviciding on the population dynamics and biting rates of Simulium damnosum (s.l.): implications for vector control as a complementary strategy for onchocerciasis elimination in Africa

et al. 2018

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BackgroundIn 2012, the World Health Organization set goals for the elimination of onchocerciasis transmission by 2020 in selected African countries. Epidemiological data and mathematical modelling have indicated that elimination may not be achieved with annual ivermectin distribution in all endemic foci. Complementary and alternative treatment strategies (ATS), including vector control, will be necessary. Implementation of vector control will require that the ecology and population dynamics of Simulium damnosum (sensu lato) be carefully considered.MethodsWe adapted our previous SIMuliid POPulation dynamics (SIMPOP) model to explore the impact of larvicidal insecticides on S. damnosum (s.l.) biting rates in different ecological contexts and to identify how frequently and for how long vector control should be continued to sustain substantive reductions in vector biting. SIMPOP was fitted to data from large-scale aerial larviciding trials in savannah sites (Ghana) and small-scale ground larviciding trials in forest areas (Cameroon). The model was validated against independent data from Burkina Faso/Côte d’Ivoire (savannah) and Bioko (forest). Scenario analysis explored the effects of ecological and programmatic factors such as pre-control daily biting rate (DBR) and larviciding scheme design on reductions and resurgences in biting rates.ResultsThe estimated efficacy of large-scale aerial larviciding in the savannah was greater than that of ground-based larviciding in the forest. Small changes in larvicidal efficacy can have large impacts on intervention success. At 93% larvicidal efficacy (a realistic value based on field trials), 10 consecutive weekly larvicidal treatments would reduce DBRs by 96% (e.g. from 400 to 16 bites/person/day). At 70% efficacy, and for 10 weekly applications, the DBR would decrease by 67% (e.g. from 400 to 132 bites/person/day). Larviciding is more likely to succeed in areas with lower water temperatures and where blackfly species have longer gonotrophic cycles.ConclusionsFocal vector control can reduce vector biting rates in settings where a high larvicidal efficacy can be achieved and an appropriate duration and frequency of larviciding can be ensured. Future work linking SIMPOP with onchocerciasis transmission models will permit evaluation of the impact of combined anti-vectorial and anti-parasitic interventions on accelerating elimination of the disease.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2864-y) contains supplementary material, which is available to authorized users.

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Evolution, epidemiology, and population genetics of black flies (Diptera: Simuliidae)

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2010

Infection, Genetics and Evolution

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Towards the Elimination of the Bioko Form of Simulium Yahense from Bioko: Planning and Insecticide Trials

Cited by 3 publications

References 7 publications

Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea

Interruption of onchocerciasis transmission in Bioko Island: Accelerating the movement from control to elimination in Equatorial Guinea

Modelling the impact of larviciding on the population dynamics and biting rates of Simulium damnosum (s.l.): implications for vector control as a complementary strategy for onchocerciasis elimination in Africa

Evolution, epidemiology, and population genetics of black flies (Diptera: Simuliidae)

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