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

1990 ◽  
Vol 328 (1251) ◽  
pp. 731-750 ◽  
Keyword(s):  
West Africa ◽  
Vector Control ◽  
Sierra Leone ◽  
Control Programme ◽  
West African ◽  
Breeding Sites ◽  
Western Area ◽  
Monsoon Winds ◽  
First Time ◽  
Onchocerciasis Control

Since vector control began in 1975, waves of Simulium sirbanum and S. damnosum s.str ., the principal vectors of severe blinding onchocerciasis in the West African savannas, have reinvaded treated rivers inside the original boundaries of the Onchocerciasis Control Programme in West Africa. Larviciding of potential source breeding sites has shown that these ‘savanna’ species are capable of travelling and carrying Onchocerca infection for at least 500 km northeastwards with the monsoon winds in the early rainy season. Vector control has, therefore, been extended progressively westwards. In 1984 the Programme embarked on a major western extension into Guinea, Sierra Leone, western Mali, Senegal and Guinea-Bissau. The transmission resulting from the reinvasion of northern Cote d’Ivoire and Burkina Faso has been reduced by over 95%, but eastern Mali has proved more difficult to protect because of sources in both Guinea and Sierra Leone. Rivers in Sierra Leone were treated for the first time in 1989 and biting and transmission rates in Sierra Leone and Guinea fell by over 90%. Because of treatment problems in some complex rapids and mountainous areas, flies still reinvaded Mali, though biting rates were approximately 70% lower than those recorded before anti-reinvasion treatments started. It was concluded that transmission in eastern Mali has now been reduced to the levels required to control onchocerciasis.

scholarly journals Patterns of epidemiology and control of onchocerciasis in West Africa

1997 ◽  
Vol 71 (2) ◽  
pp. 91-101 ◽  
Author(s):  
B. Boatin ◽  
D.H. Molyneux ◽  
J.M. Hougard ◽  
O.W. Christensen ◽  
E.S. Alley ◽  
...  
Keyword(s):  
West Africa ◽  
Vector Control ◽  
Control Strategies ◽  
Control Programme ◽  
Transmission Potential ◽  
The Public ◽  
And Control ◽  
Combined Impact ◽  
The Impact ◽  
Onchocerciasis Control

AbstractThis paper summarizes the work of the Onchocerciasis Control Programme (OCP) in West Africa, a programme which over a 22 year history has reduced the public health problems of blinding onchocerciasis in eleven countries of West Africa through vector control and, more recently, ivermectin distribution. The paper emphasizes the different approaches to control the programme has developed in the different parts of the programme area which have been determined by the epidemiology of the disease (savanna/forest form), the migratory characteristics of the vectors, intensity of the disease before commencement of treatment, the combined impact of vector control and ivermectin and the likelihood of infiltration of infective blackflies from outside the programme area. The programme has constantly monitored the impact of operations on the trends in prevalence, incidence, annual transmission potential, ocular morbidity and species of fly populations, and as a result, has identified areas where special interventions are required until the programme comes to an end in 2002. The paper illustrates the changes in intensity of infection as measured by community microfilarial load and annual transmission potential over the duration of the programme control activities. The paper also defines and justifies the control strategies in different areas and identifies areas for special interventions.

The pattern and speed of displacement of females of Simulium damnosum Theobald s.l. (Diptera: Simuliidae) across the Onchocerciasis Control Programme area of West Africa in 1977 and 1978

1985 ◽  
Vol 75 (1) ◽  
pp. 73-92 ◽  
Author(s):  
C. G. Johnson ◽  
J. F. Walsh ◽  
J. B. Davies ◽  
S. J. Clark ◽  
J. N. Perry
Keyword(s):  
West Africa ◽  
Control Programme ◽  
The South ◽  
Wet Season ◽  
Breeding Sites ◽  
Simulium Damnosum ◽  
Biting Rate ◽  
Western Border ◽  
Alternative Sources ◽  
Onchocerciasis Control

AbstractBreeding of Simulium damnosum Theobald s.1., the vector of Onchocerca volvulus, had been eliminated by 1977 from about 654 000 km2 of the Onchocerciasis Control Programme in the Volta River Basin Area (OCP) of West Africa. Nevertheless, migrating adult females continually invaded the controlled area, being blown on the prevailing south-westerly winds from uncontrolled breeding sites beyond the south-western border of the OCP area. Graphs of numbers of females caught per man per day (the daily biting rate) throughout the wet season, March to October, at 16 sites in 1977 within the OCP controlled area were remarkably similar in pattern from site to site over a range of about 500 km downwind. In 1978, only seven sites within the OCP area were similarly monitored, and the graphs were different in pattern from those in 1977, when they each consisted of three or four well-defined waves or cycles of daily biting rate which could be easily identified and traced across country, their times of occurrence lagging increasingly as the distance of the site from the south-western border of the OCP area increased. Four methods were used to demonstrate and estimate the lag: visual comparison of seasonal graphs; comparison of the mean dates of cycles at different sites and the regression of these dates on distance from the south-western border; the dates when particular cumulative percentages of the total season's catch occurred at each site and their regression on distance; and principal coordinate analysis of the data and its relation to distance from the south-western border. Statistically significant lags were demonstrated and averaged one day for every 10–30 km from the border in 1977, which indicated an average speed of migration across country. In 1978, a rate of one day per 7–35 km was indicated. Where some graphs at outlying sites were anomalous, possible alternative sources of immigrant flies are considered. The possible behaviour of flies in causing the lag is discussed.

Species composition and cyclical changes in numbers of savanna blackflies (Diptera: Simuliidae) caught by suction traps in the Onchocerciasis Control Programme area of West Africa

1982 ◽  
Vol 72 (1) ◽  
pp. 39-63 ◽  
Author(s):  
C. G. Johnson ◽  
R. W. Crosskey ◽  
J. B. Davies
Keyword(s):  
West Africa ◽  
Control Programme ◽  
General Tendency ◽  
Wet Season ◽  
Breeding Sites ◽  
Wind Speeds ◽  
Suction Traps ◽  
In Series ◽  
Air Speed ◽  
Onchocerciasis Control

AbstractTen large suction traps were operated continuously, day and night, throughout the wet season of 1977 at four widely separated places within the area of the Onchocerciasis Control Programme in the Volta River Basin (OCP) in West Africa. At least ten species of Simulium s.l. were trapped and the daily catches were analysed qualitatively and quantitatively. In the total catch of 9189 flies there were 187 males and 9002 females; among the latter only six were gravid and only five contained a full blood-meal. Cyclical changes in numbers, with periodicities ranging from 10 to 20 days, were analysed in series of overlapping Gaussian distributions, each possibly reflecting the rise and fall of a distinct population. Similar patterns in the sequence of cycles were shown by S. adersi Pomeroy, S. ruficorne Macq., S. evillense Fain, Hallot & Bafort and other species at a particular trapping site. Patterns differed between catching sites, except in the general tendency for population maxima to increase during the season. In some species, notably S. adersi, populations decreased in late July and early August before increasing greatly in September (end of the rains) prior to the October onset of the dry season. Among the species caught, S. evillense was present at all four trapping sites and particularly abundant at two of them, although the species has never been recorded before in West Africa and its early stages remain undiscovered there despite special searches for them since the capture of adult flies. By contrast, only four specimens of S. hargreavesi Gibbins were trapped although this species is abundant in local breeding sites. Diel flight periodicity was recorded over a one-week period at the extreme end of the wet season and showed that most flies were caught in the daytime; S. ruficorne showed a greater tendency to a unimodal periodicity than other species. The behaviour of flies at the time of capture is discussed, including a consideration of the local wind speeds and the air speed of Simulium s.l.

scholarly journals Status of white-necked picathartes – another reason for the conservation of the Peninsula Forest, Sierra Leone

Oryx ◽  
1993 ◽  
Vol 27 (3) ◽  
pp. 155-158 ◽  
Author(s):  
Hazell S. S. Thompson
Keyword(s):  
Sierra Leone ◽  
Human Activity ◽  
West African ◽  
Primate Species ◽  
Conservation Action ◽  
Breeding Sites ◽  
Forest Bird ◽  
Compelling Reason ◽  
Western Area

A survey of the Western Area Peninsula Forest in Sierra Leone in 1990 located eight breeding sites of the white-necked picathartes–a striking endemic West African forest bird threatened with extinction. Several breeding sites were in areas of fairly intense human activity and in danger of imminent destruction. Subsequent observations revealed successful breeding in 1990 and unsuccessful attempts in 1991. This population is probably only just viable. The discovery of Jentink's duiker–Africa's rarest duiker–in the same forest in 1988 and the presence of three threatened primate species prompted calls for urgent conservation action. The precarious status of the white-necked picathartes population provides another compelling reason for such action.

Cytotaxonomic revision of the Simulium sanctipauli subcomplex (Diptera: Simuliidae) in Guinea and the adjacent countries including descriptions of two new species

1993 ◽  
Vol 83 (2) ◽  
pp. 171-186 ◽  
Author(s):  
D.A Boakye ◽  
R.J Post ◽  
F.W Mosha ◽  
D.P Surtees ◽  
R.H.A Baker
Keyword(s):  
New Species ◽  
Sierra Leone ◽  
Sibling Species ◽  
Control Programme ◽  
West African ◽  
The West ◽  
Two New Species ◽  
Chromosomal Data ◽  
Onchocerciasis Control

AbstractThe Simulium sanctipauli Vajime & Dunbar subcomplex of the West African S. damnosum Theobald complex is cytotaxonomically revised for the western part of the Onchocerciasis Control Programme area. The subcomplex is defined and a chromosomal key provided for the identification of the sibling species and forms recognized. Two sibling species are newly described, S. leonense Boakye, Post & Mosha (Sierra Leone) and S. konkourense Boakye, Post, Mosha & Quilleévéré (Guinea and Sierra Leone). Detailed chromosomal data are provided as warranty for the conclusions about the specific or infraspecific status of the taxa recognized.

The WHO Onchocerciasis Control Programme: Retrospect and prospects

1990 ◽  
Vol 328 (1251) ◽  
pp. 721-729 ◽  
Keyword(s):  
West Africa ◽  
Insecticide Resistance ◽  
Vector Control ◽  
Species Complex ◽  
Control Programme ◽  
Related Research ◽  
Simulium Damnosum ◽  
The Future ◽  
History Of ◽  
Onchocerciasis Control

The history of onchocerciasis control in Africa and the genesis of the WHO Onchocerciasis Control Programme in West Africa (OCP) are briefly reviewed. The importance of experience gained in anti-locust campaigns in helping to plan the OCP is stressed. Members of the Simulium damnosum species complex are the vectors of onchocerciasis, which OCP is controlling with insecticide treatments on the stretches of rivers where the Simulium breed. Migrations of flies have been responsible for reinfestations of controlled areas and the spread of insecticide resistance. The management of these problems and related research are described, but it is emphasized that despite setbacks OCP is achieving its aims. A strategy for the future is outlined: vector control supplemented by chemotherapy is expected to continue until the year 2004.

scholarly journals Onchocerciasis control in Ghana (1974–2016)

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Nana-Kwadwo Biritwum ◽  
Dziedzom K. de Souza ◽  
Odame Asiedu ◽  
Benjamin Marfo ◽  
Uche Veronica Amazigo ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Vector Control ◽  
Control Strategy ◽  
Financial Support ◽  
Control Programme ◽  
Ivermectin Treatment ◽  
Mobile Community ◽  
The Mean ◽  
The Impact ◽  
Onchocerciasis Control

Abstract Background The 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. Methods In 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. Results This 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. Conclusions Despite 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.

The Royal African Company of England's West African Correspondence, 1681-1699

1993 ◽  
Vol 20 ◽  
pp. 173-184 ◽  
Author(s):  
Robin Law
Keyword(s):  
West Africa ◽  
Sierra Leone ◽  
West African ◽  
Gold Coast ◽  
Original Form ◽  
Cape Coast ◽  
General Terms ◽  
West African Coast ◽  
African Coast ◽  
History Of

This paper draws attention to an ambitious project in the publication of source material for the precolonial history of West Africa, which has recently been approved for inclusion in the Fontes Historiae Africanae series of the British Academy. In addition to self-promotion, however, I wish also to take the opportunity to air some of the problems of editorial strategy and choice which arise with regard to the editing and presentation of this material, in the hope of provoking some helpful feedback on these issues.The material to be published consists of correspondence of the Royal African Company of England relating to the West African coast in the late seventeenth century. The history of the Royal African Company (hereafter RAC) is in general terms well known, especially through the pioneering (and still not superseded) study by K.G. Davies (1957). The Company was chartered in 1672 with a legal monopoly of English trade with Africa. Its headquarters in West Africa was at Cape Coast (or, in the original form of the name, Cabo Corso) Castle on the Gold Coast, and it maintained forts or factories not only on the Gold Coast itself, but also at the Gambia, in Sierra Leone, and at Offra and Whydah on the Slave Coast. It lost its monopoly of the African trade in 1698, and thereafter went into decline, effectively ceasing to operate as a trading concern in the 1720s, although it continued to manage the English possessions on the coast of West Africa until it was replaced by a regulated company (i.e., one open to all traders), the Company of Merchants Trading to Africa, in 1750.

Displacements of Simulium damnosum and strategy of control against onchocerciasis

1979 ◽  
Vol 287 (1022) ◽  
pp. 277-288 ◽  
Keyword(s):  
Sensu Stricto ◽  
Control Programme ◽  
West African ◽  
Simulium Damnosum ◽  
Logistic Problem ◽  
Degree Of Control ◽  
High Degree ◽  
Onchocerciasis Control ◽  
Upper Volta ◽  
West African Savannah

Regular aerial treatment of 14000 km of watercourses has achieved and maintained, over an area of 700000 km 2 of West African savannah, a very high degree of control of the larvae of Simulium damnosum sensu stricto and S. sibanum , the vectors of onchocerciasis in this area. However, particular and relatively restricted parts of this area, mainly in northern Ivory Coast and neighbouring parts of Upper Volta, experience regular and prolonged reinvasions by parous female vectors, which have already taken bloodmeals (and many of them carrying the parasites) and arrive from unknown sources probably hundreds of kilometres away, from directions probably between southwest and north. This reinvasion, now experienced in three successive years, represents the outstanding scientific, epidemiological and logistic problem still facing the WHO Onchocerciasis Control Programme. An outline is presented of the multidisciplinary investigations being undertaken to find a solution.

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