Final report on the programme extension studies in Benin, Ghana and Togo

LI WORLD HEALTH ORGANIZATION AFRICAN REGION EXPERT ADVISORY COMMITTEE Second meeting Geneva 72 - 16 October 1981 ORGANISATION MONDIALE DE LA SANTE REGION DE L'AFRIQUE ocP 1EACZ.7 ORIGINAL: FRENCH ONCHOCERCIASIS CONTROL PROGRAMME IN THE VOLTA RTVER BASIN AREA PROCRAMME DE LUTTE CONTRE L'ONCHOCERCOSE DANS L,A REGION DU BASSIN DE LA VOLTA Tdl . 333.12 - 329 l0 -338.57 - T6ldx ONCHO 5241 Uv F]NAL REPORT ON THE PROGRA.},IME EXTENSION STUDIES IN BENIN, GHANA AND TOGO IocP/8r.2 ORIGINAL: FRENCH FINAL RNPORT ON THE PROGRAMME EXTENSION SIIIDIES IN BENIN, GHANA AND TOGO ocPf il.2 Page 2 CONIENTS \ 1. BACKGROUND 1.1 History .... .... L.2 Regions concerned 1.3 The Programe's terns of reference for the extension studies 2. REVIEW OF II{E EPIDEMIOLOGICJ.L STIIDIES 2.L Chronology of the medical- surveys 2.2 Epidemiology of onchocerciasis 3. REVIEW OF TIIE ENTOMOLOGICS.L STTIDIES . . 3.1 Distribution of the preimaginal vector sites Page 3 3 3 4 4 4 5 6 6 6 7 9 9 9 9 9 10 10 10 L2 13 13 t4 L4 l4 15 t6 L6 .1 Timetable of aerlal reconnnissance f1_ights . .2 Location and characteristlcs of the breeding sites . .3 Progress in the mapping of breeding sites 3.2 Dynamics of the vector populations and of onchocerciasis transmission . . . 3.2.L Setting up the evaluation network The geographical bases Pers onne 1 Evaluation methods Possible improvements to the netr^rork . . Specific composition and distribution of the S damnosum complex . Bio-ecological characteristics of the vectors. The reinvasion phenomenon.... 3.2.4 Dynamics of onchocerciasis transmission 3.3 Results of experimental larvicide applications and Iessons learned 3.4 Conclusions concerning the progress of the entomological studies . OTHERFINDINGS. . . 4.1 Hydrological studies 4.2 Aquatic monitoring COST OF THE E}TIENSION STUDIES . GENERALCONCLUSIONS. O"' 3.1 3.1 3.1 3.2.1.1 3.2.L.2 3.2.L.3 3.2.L.4 3.2.2 3.2.3 4. 5. 6. ANNEX: Plan of larviclding operations, with figures, for the extension study areas of the Prograrnme in Benin, Ghana and Togo, 1982 42 I ocPf8l "2 Page -i 1. BACKGROUND 1.1 l{istory At meetings of the Programme's Joint Coordinating Cormittee (JCC) in February L975 Lrt Abidjan and in December 1976 in Ouagadougou, a wistr was expressed by the Governments of Benin, Ghana, Ivory Coast, MaIi and Togo for the Onchocerciasis Control Programne to be extended into those parts of their countries adjacent to its boundary, as defined in the PAG Mission report. As this wish was supported by the seven Participating States in Ouagadougou in December 1976, the JCC decided in Kuwait in December L977 that preliminary studies should be conducted in Benin, Ghana and Togo for a period of two years, starting on 1 January 1978. The present report surmnarizes the studies carried out from 1978 up to 31 July 1981. 7,2 Regions concerned (Map 1) In the People's Republic of Benin the initial request concerned an area of 25 OOO km2; the area studied was subsequently increased to 46 OOO kn2. Geographically this corresponds to the entire upper and middle basins of the R. Ou6m6. At this point the sudanian savanna descends a long way southwards, and gradually gives way to guinean savanna and the pre-forest zone (what the botanists call the trDahomey gapt'). In the Republic of Ghana the areas studied are located in two administrative regicns: Brong Ahafo Region, including the right-bank tributaries of the Volta in the savanna zone of the Kintampo district arrd the west-bank tributaries of Lake Volta downstream as far as and including the R. Sene. This is an area of humid guinean savanna and pre-forest vegetation relatively hi1ly in the Kintampo district. Volta Region, which includes all the east-bank tributaries of Lake Volta between the Present southern limit of the Progranme in the north, the R. Dayi inclusive in the south, and the Togolese frontier in the east. Ihis is a mountainous region of guinean savanna in the north and pre-forest characteristics in the centre, giving way to rain- forest in the south. The data already available in the extension area requested by lvory Coast were considered adequate and the JCC authorized the irmnediate implementaLion of control measures to that area; insecticide applications began in March 19J8. , The studies of the proposed extension in I'Iali were included in the special project GCpfypOfOOt) concerning the Senegal and Gambia basins. At its meeting in Geneva in December 1979, after considering the progress report on the extension studies (document OCP/79.2) the JCC decided that two ycars be devoted to additional feasibility studies in the extension areas of Benin, Ghana and Togo, and a fu1l report would be submitted in December 1981. The total area of these two zones is estimated at some Brong Ahafo Region abour 34 OOO). 42 ooo kn2 (r/olta Region about 8ooo, In the Republic of Togo the extension area corresponds essentially to the I'lono river basin, to which the Haho and Sio basins have been added, raising the area of the zone from 23 OOO to 27 OOO km2. The region is comparable to the Beni-n zone in the Mono va11ey but is rather undulating and indeed decidely mountainous along the western fringe (Atakora). True forest appears in the south-west, while the entire Mono va1ley is included irr Ehe'tDahomey gap". It is recalled that the Ivory Coast extension covers some l1O OOO km2 plus the lower Como6 included in the insecticide treatment circuits in 1980. ocPf8L.2 PaSe 1.3 4 The Pro gralEne's terms of reference for the extension studies In Kuwait Ln 1977 the JCC accepted the p,1an of action proposed by the programme for the extension studies in 1978-1979 (document OCp/l7.2). - Medically, the objective is to collect clinical, parasitological and ophthalmologicaldata on the situation prior to vector control, following th; methodology used toi tnebasic evaluation in the onchocerciasis control programne. Entomologically, the objective is to supplement the very fragmentary knowledge of thedistribution and identity of the vectors (aerial reconnaissance at all seasons of theyear, cytotaxonomic studies) and of the dynamics of the vector populations and oncho- cerciasis transmission (using a standardized network of routine collection anddissection). These tasks PresuPPosed the setting-up of four additional operational bases and the establishment and fitting-out of four new entomological evaluation units. From the hydrological viewpoint, the national river discharge gauging networks neededto be supplemented to meet possible future needs. The participatint states concerned were to be responsible for this. On the basis of the entomologi-cal and hydrological studies it was deemed possible todraw up a proposed plan for a larviciding campaign, it being understood that the finaldecision regarding the extension would be taken by the JCC at the end of L979 in thelight of the conclusions of the feasibility study. At the sixth session of the JCC at the end of L979 in Geneva it was agreed that thestudies had shown thatrrpresent knowledge of the dynamics of blackfly populations and of the southern limit of the savanna species in the three countries concerned was not yet satisfactory.Also there were not enough hydrological data available for the comprehensive planning of alarviciding campaign and for a precise estimate of costs. precontrol data were still lacking. other matters requiring further clarification concerned the impact that the extension treatments would have on the operational costs in the initial area, the effect on the prograrrne of the reduction of the reinvasion phenomenon, and the quest for alternative methods of vector control.Qccf q. The Prograrmne's terms of reference for the second phase of the studies (1980-81) werethereby clearly defined. 2. RXVIEW OF TIIE EPIDEM]OLOGICAL STUDIES 2.1 Chronol y of the medi ca1 surveys The Prograrrne's epidemiological evaluation teams conducted surveys in the three countries concerned according to the following timetable: Benin: March 1979 0u6m6 and Okpara basins Ghana: trtay 1978 Volta Region February 1980 Brong Ahafo Region Togo: July 1977 Mono basin March 198O plateaux region (Atakpam6-Kpa1irn6) May 1981 Haho, Yoto, Zio and lower Mono basins ocP/8L.2 Page 5 2.2 Epidemiology of onchocerciasis A comprehensive and detailed report was prepared on the epidemiology of the disease in the extension study areas (documcnt OCp/EpI/8l.51); and sent to the countries in March 19g1. The section on Togo was updated and submitted to the Government at the end of June 1981. 2.2.T Benin The evaluation covered 25 villages in which 5699 people were examined (see Table 1 and Map 2). Map 2 shows the geographical location of the disease in this region: the three 1evels of endemicity which characterize a hypoendemic/mesoendemic zone north of a line joining Djougou, Parakou and Nikki, which corresponds to the water-parting between the watercourses flowing into the R. ltriger and those flowing south into the Atlantic; an onchocerciasis-free zone located between the Atlantic and a line which passes through the Zou-0u6m6 confluence and latitude 6030tN on the Mono and which constitutes the southern iimit of distribution of onchocerciasis in the Peoplers Republic of Benin I between these two zones are the major onchocerciasis foci of the 0u6m6, Zou and Okpara basins, where the disease is very severe. The focus in the Ou6m6 basin is particularly large: 3OO km 1ong, with disease prevalence everylvhere above 602 and rising to 862 in some villages and particularly high microfilarial densities ranging from 10 to 26 microfilariae per skin snip. In all the villages of this third zone the prevalence of ocular onchocerciasis exceed,s 2OZ and may be as high as 572. The proportion of subjects with irreversible eye lesions is above 1oZ in almost all the villages; it is around L5Z at Zouto. Ttris situation is reflected in theblindness rates, which vary on average from LZ to 42. In the river basins of the Kouffo I and the Mono in the extreme south, the foci are less severe, thomicrofilarial skin counts are 1ow, irreversible eye lesions are rare, and theblindness rates are very low. 2.2.2 Ghana The evaluation covered 29 villages in which 7260 people were examined. - In Volta Region, 4032 persons in 12 villages were examined in two foci (see Table 2 and Map 3). In the Asukawkaw focus the disease is rife in a severe form throughout the basin: in all the villages examined 65 - 712 of individuals were infected with O. volvulus and half thepopulation generally became i nfected before the age of 10 years. I'Iicrofilarial densities arehigh: 1O to 12 mf per skin snip. The ophthalmological indices show thar over 442 cf the villagers have microfilariae in the anterior chamber of the eye and LOZ have irreversible eve lesions. The average blindness rate is in excess of LZ. The villages of the Dayi focus, on the other hand, are characterized by low prevalence, very 1ow microfilarial densities, a 1ow rate of microfilaria carriers in the eye and the almost complete absence of blindness. Nevertheless, many cases of severe onchocerciasis are imported into these villages by migrants who originate from the area but have spent severalyears in the Asukawkaw cocoa plantations (see map). In Volta Region, therefore, the southern limit of severe onchocerciasis passes betweenthe Asukawkaw and Dayi basins, which would seem to reflect the lower density of the savanna species and the smaller and more widely spaced breeding sites along the lower and middle Dayi ocP / 8L.2 page 6 species and the smaller and more widely spaced breeding sites along the lower and middle Dayi - In Brong Ahafo Region, 3228 people in 17 villages were examined (see Table 3 and Map 4). The disease is very severe in the Black Volta basin and on the lower reaches of some of its tributaries (Tain, Pr.unpum) and particularly in the Pru basin. On this watercourse, in the village of Asubende, prevalence is 77.22:'5OZ of the inhabitants become infected with the parasite before the age of 11; mean microfilarial density reaches the record figure of 34.3 and the blindness rate is as high as 62. The disease is socially apparent without reaching an intolerable level in a vast central zone comprising the upper course of the tributaries of the Black Volta and the Sene and the Urukwain watercourses. The southern limit of this zone seems to be latitude 7o3otN. The disease is perfectly well tolerated south of latitude 7o3OtN, since it is virtually non-existent there. 2.2.3 Togo The evaluation covered 30 villages in which 6236 people were examined (see Table 4). Map 5 shows the pattern of endemic onchocerciasis in the extension study area of Togo. Onchocerciasis is particularly severe in three-quarters of the Mono and M6 basins. Half the population is infected with the parasite before the age of seven years at T6t6tou on the Mono, where prevalence is 82.42, and before the age of 1o years at otsanani Ad6dakope on the Amou, where prevalence is 81.52. On the Sio, Haho and Yoto basins the disease is also severe but strictly circumscribed to the Tokpo focus on the Sio, where prevalence is 862, and to the Yoto-Kop6 focus at the confluence of the Haho and Yoto, where prevalence is 69.62. In all these foci severe ocular onchocerciasis varies between L2Z and 16Z. On the other hand, the mountain villages with one exception (Dayes-Djodji on the Gban Houo have 1ow microfilarial counts and Iow incidence of severe eye lesions, despite comparatively high prevalence figures of a Eypically hyperendemic level; similarly, in the other plateau foci(basins of the upper Asukawkaw, Domi and Ov6) where onchocerciasis is also hyperendemic, it again seems less troublesome than in the plains and for the same reasons. A line joining Avedj6 (6o29t ) on the Sio, Ess6-Nadj6 (6035') on the Haho, and Akladjenou(60371 ) on the Mono (and extending along latitude 6030tN into Benin) would appear to constitute the southern limit of severe onchocerciasis in Togo. Onchocerciasis is a real public health problem in Togo; with the exception of the Maritime Region, very few areas are genuinely free fronr it; almost 12 of the population of southern Togo is blind. REVIEW OF THE ENTOMOLOGICAI STUDIES 1 Distribution of the pre- imaginal vector sites 3.1.1 Timetable of aerial reconnaissance flights A very large number of breeding site inspections was carried out at ground level during the four years. In addition, the following reconnaissance flights r{ere made by helicopter. - Entire Mono basin (Togo): 17-26 January 1978 - Basins of the Pru (Brong Ahafo Region), Pra and Ankobra (south-west Ghana) : 11-14 April 1978 - Ou6m6, Okpara and Zou basins (Benin): L9-2O July 1978 - Idem, 5-7 December 1978 - Mono and Sio basins (southern Togo): 14-15 June 1979 3 3 ocP /87 .2 page 7 - Right-bank tributaries of the Ou6m6 (Zou, Adjiro, Odola, T6rou (Benin): 2l-22 August L979 - Pasa, Kpaza (Volta Region, Ghana), Aou and Ani6 (tributaries of the Mono, in Togo): 17-18 May 1980 - Southern part of the Ou6m6 basin (Benin): 4-6 July 1980 - Mono, Sio, Haho and Amou (southern Togo): 11-12 July 1980 - East-bank tributaries of Lake Volta (Dayi and Asukawkaw basins, Volta Region): 13 July 1980 - Mono basin (Togo): 17, 18, 23 and 26 M.ay, 12, 13, 27 and 28 June, 18 and 19 July, 2 and 3 August 1980 - Ou6m6 basin (Benin): 2L-22 YIay, l-2 August 1980 - Tributary of the Mono (southern Togo), Asukawkaw and Dayi basins (Volta Region, Ghana) : 2 March 1981 - Volta Region and Brong Ahafo Region (Ghana) I 6-9 May 1981 - Upper basins of the Atakora massif (Togo and Volta Region): 5-5 June 1981 - Lower Mono, Ani6, Amou (Togo): 12 June 1981 - River Mono (Togo): 15 June 1981 - Mono and Asukawkaw basins (Togo and Ghana): 22-25 June 1981 - Upper basin of the 0u6m6 (Benin): 26-27 June 1981 - Mono and Asukawkaw basins (Togo); 2-3 July 198I - Mono and M6 basins (Togo) t LO-12 July 1981 - Lower Ou6m6, T6rou, Okpara and tributaries (Benin): 17-18 July 1981 - M6 and tributaries (Togo): 21 July l98l - Lower Mono basin (Togo): 23 July 1981 3.1.2 Location and characteristics of the breeding sites (see Map 6) in the S. damnosum are found on a large On all the rivers and coastal watercourses, the breeding sites extend southwards to r^'ithin a few dozen kilometres of the Atlantic coast. 3,7.2.1 Benin rn the ou6m6 basin, the ou6m6 itself, the okpara, the Zou and their tributaries offervery favourable conditions for the development of the onchocerciasis vectorsl river flow ceasesfor two to four months in the dry season on the ou6m6 upstream from Sav6 bridge and alongthe entire course of the tributaries. Throughout the entire period of river flow the bed,which is interrupted by^si11s of crystalline rock, forms complexes of natural breeding sites asfar south as latitude- 7o23tN, si.tes that are sometimes comparable to those on the Black Voitaand the L6raba; downstream frorn this latitude the ou6m6 has only isolated breeding sites(at Zagnanado and Sagon, for. example). on the okpara the breeding sites are widery spaced along the upper and middLe reaches, butbecome very numerous on the lower reaches when the river leaves the Nigerian border. Conditions favourable to the pre-imaginal developuent of species complex (high current speed and presence of substrates for attachment) number of watercourses. The Zou has many breeding sites along its middle reacheslbut despite the gentle slope breeding sites nray be created by at periods of high v/ater. A11 the other tributaries of these three watercourses (see maps) frow from mid-June toNovember or December, with a maximum in september, and harbour a large number of breeding sitesthror,rghout this period, The Kouffo t has rocky breeding sites along a stretch of some 25 km upstream from theAbomey-Aplahou6 road, owing to the ptesence of rock sills. its lower reaches are meandering, the speeding-up of river f lor,r ocP / 81.2 page 8 3.1.2.2 Ghana rn Volta Region pre-imaginal development of the S. damnosum complex occurs in the basins of the Kpaza, Chain, Wulubong, Asukawkaw, Konsu and Dayi (east-bank tributaries of Lake Vo1ta,going from north to south). In this region of guinean savanna and mountainous pre-forest characteristics (Atakora) all these rivers have very steep slopes (with torrent tracts in their upper reaches) and except on their very lowest and stagnant reaches (1ow valleys flooded by the lake) they offerinnumerable possibilities for breeding sitesl "orn. ut. permanent rivers (Kpaza, Asukawkaw, Dayi and some of their tributaries ), but there are many gaps in our hydrological knowledge of VoltaRegion and it is not yet knovrn whether many of the smal1 tributaries and sub-tributaries arepermanent or not. A11 the watercourses are at their fullest in August, and emphasis must beplaced on the host of rainy-season breeding sites (Ju1y to September) on tiny seasonaltributaries. The critical rivers in Brong Ahafo Region are firstly the minor south-to-north tributaries of the Volta in the hi11y region around Kintampo (Oyoko, Pumpum) and secondly the largertributaries of the west bank of the lake (Pru and Sene basins), in particular along their middle and lower reaches. The other tributaries of the north-western arm of the lake do not seem tobe affected, and the areas with large breeding sites are limited to the stretches of water already mentioned. It should be borne in mind that the breeding sites in the Tain basin have already been included in the Progranrnets regular treatment schedule. rt is understood that breeding sites of the S. darnnosum complex are also present in Ghana along the watercourses south of the Tain, Sene."a5ryi, U,rt these southern regions were excluded from the studies because of their epidemiological characteristics (see section 2) and the identity of the local vectors (see section 3.2.2); moreover, these areas were notincluded in the Ghanaian request. 3.1.2.3 Togo Mono basin: In the dry season, only the section dovrnstream from the confluence with the Amou has breeding sites as far as latitude 6048tN; the remainder of this watercourse and aI1the tributaries (except for the Pasa and the Amou) dry up from January to April; in those months the waters of the Mono are derived solely from its tributary, the Amou, which has its headwaters in the Atakora plateau region. The Mono itself has many breeding sites and "ribbon sites" during the rainyseason; however,breeding sites are rare between Tchamba and Kpessi where the river flows on a sandy bed; from a point 20 km upstream from Kpessi and as far as latitude 6o48rN (1ast site downstream) the bed of the Mono is intersected by many rapids, all of which are favourable locations for the development of S. damnosum s.1. ; the largest of these rapids is downstream from T6t6tou on the lower reaches of the river. The upper basin of the Mono in the vicinity of Sokod6 is a maze of tiny tributaries that start in the Atakora hil1s and contain many seasonal breeding sites. One tributary, the Pasa, is a permanent river and has been included in the progrannners treatment circuit during the dry season in an attempt to prevent the northward dispersion of vectors from this rr/atercourse. The Ani6, particularly its lower ha1f, is a watercourse very favourable to the development of the onchocerciasis vectorsl the same does not apply to the Ogou, a left-bank tributary of the Mono with a sandy bed and very few rapids. In southern Togo the Sio and Haho are S. damnosum s l. rivers only for the upper half of their course, which passes through a typical forest region. These two rivers, which dry up during the dry season, form two systems independent from the Mono system. Their lower reaches flow through almost flat terrain which is geologically related to the clay-sand complex at the edge of the continental platform. ocP/8t.2 page 9 3.1.3 Progress in the mapping of breeding sites Knowledge of the geographical distribution of the breeding sites is sufficiently advanced to determine the length in kilometres of the rivers that are subject to vector reproduction and thus require larviciding treatmerrts in the event of a control campaign. The total lengths of the stretches to be treated are as follows (see map): People's Republic of Benin; 2365 km in the rainy season and 34O km in the dry season. Republic of Ghana: 1715 km in the rainy season (710 in Volta Region, 1005 in Brong Ahafo Region) and 95O km in the dry season (29O in Volta Region and 66O in Brong Ahafo Region). Republic of Togo: 18OO km in the rainy season and 32O km in the dry season. This makes a total of 5830 km in the rainy season and 1610 km in the dry season (ratio 3.6:1) compared with 18 OOO and 6000 km respectively (ratio 3:1) in the zone currently under treatment by the Progranrne. Ihe comparatively high figure for the dry season is accounted for by Volta Region, which acts like a permanent reservoir and where the lack of information as to whether the tributaries are permanent makes it necessary to put low-water estimates at the maximum level. There is also enough knowledge to draw up detailed maps showing the location of breeding sites at the main seasons, on a scale suitable for routine use by the Progranrne's pilots throughout the study area of Benin, in the majority of the Togolese study area and in Brong Ahafo Region; the mapping will be completed between August and October next. The same cannot be said for the mountainous areas of the Atakora (west-south-western Togo and Volta Region in Ghana) where the innumerable sma11 rainy-season tributaries are difficult to catalogue. The situation is distinctly worrying in Volta Region, where there are no reliable topographical maps on an adequate scale and where data on relief and on the courses oI rivers will have to be collected by air by Prograrmne staff in a region which is at the same time the hilliest and most densely wooded region and the one most abundantly supplied with rapids. 3.2 Dynamics of the vector populations and of onchocerciasis transmission 3.2.L Setting gp the evaluation network 3 .2 .L.L The geographical bases In accordance with decisions taken by the JCC at its fourth sessj.on, (Kuwait, 1977) the Progranrne has set up four entomological evaluation subsectors in the following localiti,es in tlre extension study areas: - Atakpam6 (Togo), opened on 12 June 1978 and attached to the Lama-Kara sector; - Hohoe (Volta Region) and Kintampo (Brong Ahafo Region) in Ghana, localities that werepreferred for logisEic reasons to the iniEially selected sites at Wenchi and Jasikan; opened on 1 June 7978 and 5 March 1979 respectively, these two subsectors led t6 the closure of the Yendi and 8o16 subsectors situated further north in the area already under larvicide treatment and like the latter were attached to the Tamale sector. - Parakou (Benin), opened on 7 April 1979 and attached to the Natitingou sector. 3 .2 .1.2 Personne 1 The organization of each subsector in the extension study areas is modelled on that of the subsectors of the Progrannne area under treatment and consists of an entomol-ogy technician as subsector chief, an auxiliary, a radio operator, an assistant mechanic, five drj-vers, eight insect collectors and two caretakers. ocP/8t.2 page 10 Each of the four subsectors has the same basic equipment (vehicles, optical equi.pment, laboratory apparatus, generator, etc.) as the subsectors in the area under treatment and is linked by VHF radio to all the Progranme's sectors and subsectors and to Headquarters in Ouagadougou. 3.2.L.3 Evaluation methods These methods, which are identical in every respect to those used in the programme area under treatment, consist of standardized catches of biting blackfly at control points. Thus 75 collection points have been selected as representative of aL1 the epidemiological andhydrological patterns in the extension study areas; they have been divided into rrweekly pointsrt visited one day each week, rrfortnightly poinEsrr visited once every two weeks, and'toccasionalpointsn for supplementary investigations. A significant Proportion of the blackflies caught is dissected by the standardized methods that have been in use within the Progranure since 1975. These dissections provide routineinformation on the presumed origin of the species (with much difficulty in the region concerned; see section 3.1.2), the mean physiological age of the populations and their natural rates ofinfestation with O. volvulus. The ultimate aim is to quantify over a given period the bites of S. damnosum s.1. (A3R or I'IBR: annual or monthly biting rates) and the theoretical intensity of transmission (ATP or MTP: annual or monthly transmission potentials) for purposes of comparison. The subsector teams are also responsible for the weekly checks on the preimaginal a certain number of control points accessible by land and for the reading (also weekly) existing river discharge gauges. sites at of the 3 .2 .L.4 Possible i.mprovement s to the network As a result of the acquisition of medical data and gradually improved knowledge of theplaces where transmission is highest, the collection network set up for the collection ofpre-larviciding data may be regarded as satisfactory and reliable. If surveillance should continue for a number of years, however, certain readjustments would be desirable: - Since the extension area in Benin stretches so far to the south it would be wise to divide the present Parakou subsector into two, by opening an additional subsector at Bohicon for example; some of the personnel from the Porga subsector could be used for this purpose. It would then be preferable to transfer the sector headquarters from NatitinSou to Parakou for logistic reasons (more central geographical situation). - Similarly, the Atakpam6 subsector covers a very wide latitude and responsibility for some of its surveillance points should be reallocated to the Lama-Kara subsector. - Some reduction in the netrrork could be made in Volta Region if the experi-mental larviciding treatments reveal no anomalies between neighbouring coLlection points. 3.2.2 Specific composition and distribution of the S. damnosum complex (see map) In order to establish what species of the complex are present and Eo determine theirdistribution, a very large number of chromosomal identifications have been conducted on thelarvae (the only reliable method of species identification), both larvae caught in the wild state (the majority) and larvae bred from biting females. Identification trials haVe also been conducted on the basis of micro-morphological characters. The equatio+ ttwing tufts with dark dominant = species with forest affinities and wing tufts with pale dominant = savanna speciesil , which is currently accepted and routinely utilized in the Progranme area under treatment, is found lacking in the south-eastern part ofthe Prograrme area. In this district there is clearly a rrvarieEy" of S. soubrense (a species ocPfil.2 page 1r reputed to have forest affinities) with pale wing tufts which may become establisheci in the savanna, while the species S. squamosum (which tends to have forest affinities but is fairly ubiquitous) appears to have two distinct forms, one with light wing tufts and the other with dark wing tufts. Routine nrorphological identification of the approximate geographical origin of ttre biti-ng females would therefore seem impossible from the outset in the extension study areas. at least if the Progranmre's conventional criteria are used. All that currently seems possible is to identify populations (and not individuals) from such sophisticated criteria as the ratio beil,reen antenna length and thorax length. The cytotaxonomic studies have revealed the presence of six species of the S. damnosum complex; S. damnosqq s.s. and S. sirbanum (species with savanna preferences), S. squamosum(a sma11-river species, relatively ubiquitous in its phytogeographical patterns, but with forest affinities) and S. yahense (characteristic species of sma11 forest watercourses) , S. sanctipauli (norma1Ly found in large forest watercourses) and S. soubrense (characteristic of the large rivers, mainly in the forest, but is also able to develop in the same type of watercourse in the guinean and even sudanian savanna; many specialists hold that this species and the preceding one are a single entity). S. damnosum s.s., ubiquitous to a1l- the bioclimatic zones, is welL represented everywhere, from the upper reaches of the rivers and tributaries to the last breeding sites downstream (Volta, Mono, Ou6m6, Sio, Haho, Kouffo) and on the tributaries of Lake Volta and the Black Volta; the species appears to be infrequent in southern Ghana. - S. sirbanum is plentiful ln the upper basins of the major rivers (Mono, Ou6m6 and tributaries) and on the Kpaza, but gradually becomes more scarce towards the south, although it reaches latitude 7'30' N (Ou6md and Mono). This species has been reported on the Volta at the Senchi rapids and on the Pru, but is uncommon in Volta Region and seems to be completely absent from the Kintampo district. - S. squamosum is plentiful only in Brong Ahafo Region and on sma1l tributaries (or the uPper reaches of large rratercourses) originating in the Atakora throughout Volta Region and in the Mono and Sio basin. Towards the south this species is present in the lowest downstream sites on the Volta, Sio and l,Iono, but in the east it does not seem to reach the Ou6m6 basin (with one exception, on the extreme upper reaches of this river). - S. yahense is reported only from the south of Volta Region (River Dayi), but is regularly present on the sma11 tributaries in the forest regions of Ghana south of Brong Ahafo Region and in the vicinity of Akosombo, where the Volta seems to denote its eastern limit. - S. sanctipauli extends a remarkably long way northward (by comparison with tht: vTestern zone of the Progranrne) in the Ou6m6 basin (8"30'N on the Okpara and even 9o on- ihe T6rou) and the Mono and Asukawkaw basins (8'inboth cases) and is well represented on the lower reaches of these three rivers and of the Volta (Senchi rapids) and on the coastal rivers of southern Ghana. - S. soubrense , whi,ch is also widely represented on all the middle sections of the large rivers flowing into the Atlantic, moves northward in the ralny season along the Mono, the Ou6m6 and their tributaries as far as tl-re latitudes of Lama-Kara and parakou(extreme known limi.t 9'30' N); the species is replaced by S. qancr:lpauli in the forest zone in the south of Volta Region; it is present on the Volta downstream from Akosombobut has not been reported from Brong Ahafo Region (or from any other part of central Ghana, whether treated or not). When the extension studies began, the Programme paid speciaL attentron te the two savanna species, which are always associated with severe onchocerciasis in their originalbioclimatic zone and are also capable of substantial and dangerous seasonal migraticns. Infact the limit of the distribution of S. damnosum s.s. and S determine the southern limit of the extension projects. sirbanum was intended to ocP/8t.2 page 12 While the importance of these species cannot be denied, it has since been found that the closest attention must also be paid to the presence and relative importance of three other species: - S. squamosum, which in Togo is responsible for large-scaIe seasonaL reinvasion (May to September) at the southern boundary of the present OCP larviciding zone. anc ti auli and above all S. soubrense (more ubiquitous), in which resistance to temephos was detected and subsequently developed in other parts of Africa (particularlyin Ivory Coast in the OCP extension area) only a few months after routine Abate applications were introduced (1980). Accordingly, since there are no longer two but five epidemiologically dangerous species, and since these sPecies are widely s5rmpatric, the limits of the areas where there is a serious risk of transmission or which represent a potential source of recolonization are as follows: east of Lake Volta, the distribution limits of the complex in the south and the Nigerian borderin the east; west of Lake Volta the boundary is the water-parting between the Tain, pru andSene basins in the north and the Bia, Tano, Ofin and Afram basins in the south. 3 .2.3 Bio-eco logical charac teristics of the vectors. The reinvasion phenomenon The biting rate, mean life-span, dispersion and zoophilic tendencies of the various species revealed no new features as compared with the knowledge of these comparable bioclimatic zones. females of the same species in Broadly sPeaking, the biting populations display a,tpeakrrin the rainy season which culminates in September in most foci (earlier in Volta Region); they are plentiful everywherebut there is a relative 1u11 or interruption, varying in extent and duration according to thelow-water level or drying-up of the Mono and Ou6m6 basins (see Tables 5, 7 and 9). The proportions of old (parous) females are much higher in the dry season than in the rainy season, but in the northern part of the study areas of Togo and Benin the start of the rainy season is often marked by a sudden rise in average age, which reflects a reinvasion. The annual biting rates (A3R: see Tables 5r 7 atd 9) are substantial everywhere, in Particular on the southern reaches (at T6t6tou, on the Mono, over 1Oo ooo bLtes/nan/year), in certain high valleys (Djodji: over 235 ooo), which is to be expected, and also in the savanna valleys (over 1OO OOO in the Ou6m6 basin) ; at 87% of the collection poinrs the ABR is abovethe threshold of looo bites/^^n/y"^, regarded as the theoretical threshold of acceptability, and at 52% of these the ABR is more than 10 OOO. By comparison with the reinvasion that has been described in the west of the prograrrne area, the reinvasion affecting Togo (va1leys of the M6, Kara and K6ran and the upper basin of the Mono) from May to september displays the following special features: - the species concerned are different; the two savanna species are also involved here andS. soubrense is occasionally reported, but the reinvasionrrllaygsrr consist mainly of S. squamosuml - the general direction seems to be south-to-north (instead of south-west-to-north-east); - the sources of reinvasion are undoubtedly less distant than in the west, and it seems likely that they are situated in the hil1y areas of the Atakora, in the river systems of VoLta Region and the Togolese plateaux; it is impossible to be more precise atpresent. In Benin reinvasion is also affecting the Prograrrne area under treatment, particularly on the Sota (Gbass6), Iran6, Alibori and l'16krou, at all seasons. This is an apparently typical rej.nvasion (parous females of savanna species), the source of which is still completely unknovrn; the nearby untreated watercourses in Nigeria are not ruled out. ocP/8L.2 Page 13 3.2.4 Dynamics of onchocerclaqis lrane4lsqloq The vector characteristics do not seem tc differ from those of the same species in other West African foci with the same bioclimatic features: the mean microfilarial densities are around two in the foci where the savanna species predominaEe (Mono, Ou6m6, Pru) ; they are between three and four in the foci of S. squamosum (Kint ampo, Togolese plateaux) and between four and five for S. soubrense-sanctipauli (Asukawkaw, lower Mono) and S. yahense (Vo1ta Region) . An important specific feature concerns the vectorial capacity ofS soubrense in the Savanna zones, where the species already exists and where it is capable of increasing in importance if it should becorne selected resistant. The first indications seem to show a vectorial capaclty that is less good than for the savanna species but is not negligible for all that. Research is continuing and will be extended. The transmission rates are high almost everywhere (,see Tables 6, 8 and lO and Map 8): 69% of the collection points have ATPs above 10O larvae/marr/year (document OCP/SAP/77.L); at 42% of these collection points the ATPs are above 1OOO larvae/man/year, a value which in the savanna i-s unquestionably associated with the most severe clinical and socioeconomic manifestations of the disease. The ATP values are parti-cularly high (2OOO to 8OOO) in the upper and especially the middle basins of the 0u6m6 (Ou6m6, Okpara, Zow, T6rou, Beffa, W6w6) and throughout the Mono basin (Mono, Ani6, Ogou, Amou) and on the Pru (Tables 61 8, 10). In comparable savanna zones of other West African foci such ATP values are associated with the absence of human settlements and with top-1evel hyperendemicity. The ATP values are highes! in the forest zones, at low latitude (8OOO - 15 0OO larvae/man/year on the the Gban Houo). the mountain ranges and the large valleys lower Mono, in the Asukawkaw basin and on In the Mono and Ou6m6 basins transmission shows a marked annual 1ow or even an interruption(the duration of which is inversely proportional to the size of the watercourse) in the dry season (two to four months between Janua,ry and April). The maximum generally appears in August (frequently over 1O0O larvae/man/month), but an early peak often occurs in May-June in the northern half of the basins (influence of reinvasion). On the rivers of the Togolese plateau and Volta Region, on the other hand, transmission is continuous and reaches a peak in the dry season between November and February, varying according to the watercourse and the year (frequently in excess of looO L^ruu"/^^n/^o"it). The valleys of Brong Ahafo Region display fluctuations of either type or a combination of the trro (bimodal curve). 3.3 Results of experimental laryrclle eppllcations and lessoqs learned These treatments were carried out at the start of the rainy season in the upper basin of the Mono (1980) and later in the upper and middle basins of the Mono and in the Asukawkaw and Bassa basins (1981). The objectives were threefold: - to test the practical possibility of larviciding in mountainous and wooded regions which are badly mapped and have no discharge garrging network; to determine the Iocal effects of such larviciding; to study the impact on the reinvasion of areas further north. It proved possible to treat the main watercourses effectively, even in the mountains, despite the logistic difficulties and the fact that the lack of gauging stations may present a serious handicap if a larvicide less specific than Abate is used. On the other hand, aerial ocP/8L.2 Page 14 larviciding of sma11 tributaries in the rainy season is technically difficult and virtually impossible without proper maps. The effects of these treatments on the biting populations r.rere seen very rapidly and in some parts of the mountainous areas of Atakora were very substantial. Owing to the persistence of productive breeding sites in the area under treatment, not only on the smal1 tributaries in the mountainous areas but also on the Mono, reinvasi.on was not completely halted south of Lama-Kara even though it was considerably reduced. 3.4 Conclusions conc erning the proqress of the en logical studies Knowledge of the distribution of the breeding sites of the vector species is satisfactory. It proved sufficient for the determination of the limits of distribution of the S. damnosum complex and the selective distribution of the six species of which it is comprised; in addition this information made it possible to determine the critical rivers and to outline the strategy and the treatment resources (fixed-wing aircraft and helicopter flying hours,quantity of fue1, requirements of various larvicides, fuel and larvicide depots) that would be needed if a larviciding campaign were launched in the extension study areas. The detailed mapping on a scale of 1:2OO OOO still does not provide satisfactory coverage of the mountainous areas in the rainy season, particularly in Volta Region where the drainage system has not yet been mapped. Pre-control data on the dynamics of the biting populations and on onchocerciasis transmission are extremely plentiful (they will soon cover three full annual cycles at manylocations) and of excellent quality. They provide a comprehensive and reliable reference basefor comparative studies to evaluate any future control. The entomological data ta11y most satisfactorily with the medical evaluation data. WhiIethis agreement was foreseeable in the savanna, it could not be taken for granted at lowerlatitudes or at high altitude. It is a well-knor,m fact that the correlation between AIp values and the severity of the disease in the foci of the forest vectors is not at all comparable withthe correlation in the savanna, and that high and even extreme ATP levels are not necessarily associated with clinically and socially intolerable onchocerciasis. The fact that a good correlation between entomological and medical findings was mainlained in the areas under consideration is no doubt related to the fact that there is nowhere a singl-e-species vectorpopulation. Nevertheless it should be noted that ATP 1evel of a few thousands are associ.ated with abandoned valleys in the savanna foci (Ou6m6), while ATP levels of 15 OOO were recordedfor hyperendemic vilLages alongside watercourses in the mountain areas. If larviciding is carried out, therefore, it will be useful to keep a very close watch onthe impact which the reduction or complete control of the vector populations, particularly inhigh areas, produces on a type of onchocerciasis characterized by the transmission of very large numbers of infective larvae, a high prevalence with but normally moderate severity(microfilarial densities low, severe eye lesions rare); it is quite possible that differences may then apPear between the findings of entomological evaluation and medical evaluation, the significance of the ATP under such epidemiological conditions needing to be redefined. 4. oTHER FINDINGS 4.1 Hvdrolosica 1 studies The existence of a good basic network of gauging stations, at least on the main rivers tobe treated, is absolutely essential if a larviciding campaign is to be considered. In L977 the extension study area had three serviceable gauging stations in Benin, three inGhana and 13 in Togo, and these three countries were requested to supplement their networks by setting up and calibrating further gauging stations. The national services were asked for eight new stations in Benin, eight in Ghana, and four in Togo. ocPf 8L.2 page 15 At the 1979 session of the JCC the hydrological data was considered insufficientrrfor the comprehensive planning of a larviciding campaign and for a precise estimate of costs". The present situation of the installation work is shor,rn in Table 11 and Map 9. In Benin definite progress should be achieved during the present rainy season through a Benin{RSTOM{CP agreement established early in 1981: it is anticipated that by the encl of 1981 calibration curves will have been prepared fcr six of the eight new stations requested' In Ghana no stations have so far been calibrated and several need to be constructed or reconstructed (somegauges set up in 1978 by the nati.onal services and since destroyed by flood waters). Despite the work undertaken in 1981 with material and logistic assistance from OCP the situation is causing concern because a serviceable network will- not be ready fot L982. In Togo, as a result of the final work carried out in 198O-81 by the national services, the network is highly satisfactory. Although incomplete, these networks and the data relating to them have made it Possible to reach a satisfactory approximation (although necessarily a rather vague approximation in Ghana) of the practical arrangements for an aerial larviciding campaign and of the detailed costs of such an operation. Nevertheless, if such a project is to be routinely implemented on the basis of weekly aerial circuits, it is absolutely essential to have calibration curves available in good time, especially if larvicides other than Abate are considered for application. 4.2 Aquatic monitoring It is now inconceivable to undertake a larviciding campaign in running water without conducting a prior study of the lotic fauna and without simultaneously conducting a continuing study on the impact of larviciding on aquatic insects and fish. In 1977 -L978 the Ou6m6, Okpara, I'Iono, Ani6, Dayi, Menu, Wawa, Asukawkaw and Pru were visited by consultant hydrobiologists. ln Ghana the locations of Asubend6 (Pru), Asukawkaw ferry and more recently the Menu have for several years been subjected to regu.1-ar monitoring by the team from the Institute of Aquatic Biology at Achimota, under a contractual- agreement with the Progranrne which is renewed annrrally. On the Sio a Togolese national team is continuing its hydrobiological research for the University of Benin (Lom6). The Progranrne has also provided specialization study grants for three experts in invertebrates from Ghana, Togo and Benin and for three Beninois technicians. An agrecment is being negotiated in order to provide a training grant for a Beninois ichthyologist, and there is a similar opportuni.ty for a candidate from Togo. In late 1980 and early 1981 OCP consultants on invertebrates and ichthyology drew up an outline progranEne and timetable for aquatic monitoring in the extension study areas of Benin and Togo, and carried out initial field surveys in the dry season with the newly established national teams. On the basis of the consultants'recomnendations the protocols were drawn rrp for two annual contractual agreements, including the financing of the hydrobiological teams in Togo and Benin by the Prograrrrne and are currently being studied in Lom6 and Cotonou. It is hoped that at least one survey can be carri.ed out in the 1981 rainy season, if necessary with the collaboration of Progranrne consultants. ocP /8t .2 page 16 In any case it seems that, with the exception of Ghana where routine aquatic monitoringhas been in progress at several points in the extension study areas for a number of years, thepre-larviciding hydrobiological data (inventory of fauna, population dynamics) are as yet extremely fra8mentary if not non-existent: in particular there is no complete annual observation cycle for either Togo or Benin, although this is the minimum normally insisted onby the hydrobiologists for serious monitoring, before the larviciding of rivers begins. 5. COST OF THE EXTENSION STUDIES At the JCC session in December 1977 a total of $ 3 527 7oo was approved for an extensionto the Prograrrne in Ivory Coast and for extension studies in Benin, Ghana, Mali and Togo for atwo-year period beginning on 1 January 1978. The cost of the extension activities in Ivory Coast was estimated at $ 2 345 1OO. amount earmarked for the "Extension studiesrr proper was therefore $ 3 527 7OO - $ 2 345$ 1 182 600. The net 1OO = At the sixth session of the JCC in December L97g it was decided to extend these studies fortwo further years until December 1981. Expenditure during the first two years had been lowerthan the initial estimates on account of the delay in setting up the entomological surveillance subsectors and because of reduced requirements for flying hours and for external consultants.The savings thus made were used to finance a large proportion of the third year (19go) of these studies (for details see TabIe 12). Although funds were initially allocated for Mali, the progranme is no longer directlyinvolved now that this extension area has been included in the feasibility study for an onchocerciasis control campaign in the Senegal river basin area (project 1c.p/fupO/ml). Additional financing for an amount of $ 437 2oo was approved at the first session of theJoint Progranrne Conrnittee (JPC) in Yamoussoukro in 1980 for the continuation of the studies inBenin, Ghana and Togo in 1981, as had been proposed at the 1979 meeting of the JCC. 6. GENERAL CONCLUSIONS ( 1) The medical surveys and entomological evaluations carried out by the progrartrne over afour-year period amply demonstrate that the four zones proposed for larviciding extension studies in Benin, Ghana and Togo all contain, or consist entirely of, hyperendemic foci of onchocerciasis where transmission and the disease can be at least as severe as in foci under- treatment further north and are sometimes socially intolerable. (2) The distribution and identity of the vectors and their respective vectoriaL capacities are sufficiently well known in the various foci, and good quantitative entomological data (ABR and ATP) as reference are now available for a longitudinal study of the blackfly nuisance and of onchocerciasis transmission in the event of larviciding. (3) The application of larvicides by air to the infected watercourses seems technically feasible, even taking into account the orographic, hydrological and phytogeographical conditions prevailing in part of the areas studied (Atakora massif), which might require a special logistical approach. (4) The entomological and hydrological data collected have made it possible to define a larviciding strategy for the areas studied, to plan a campaign project in detail and to make a fairly close estimate of the cost (see Annex). (5) Although there is every reason to believe that the extension of larviciding into the study areas would help to neutralize the seasonal reinvasion of northern Togo, it is sti11 difficult to foresee precisely what other benefits the extensions could produce for the area of the programne currently under treatment. ocP/8L.2 page 17 (6) Despite the data recently acquired or about to be acquired, some essential data(topographical maps, river discharge gauging stations and measurements) are sti11 not available in some places, which Prevents the early introduction of weekly larviciding circuits under conditions that guarantee sati-sfactory safety and efficacy. (7) The hydrobiological pre-control data are sti11 very fragmentary for the majority of the river systems concerned and are distinctly inadequate to serve as reference material for continuous monitoring of the aquatic fauna after larviciding begins. (8) S. soubrense-sanctipauli is very widely distributed in the extension study zones east of Lake Volta. It has been known for only just over a year that this species, which incidentally is capable of transmitting onchocerciasis in a variety of bioclimaEic zones, is also capable of developing temephos-resistant populations after a very short period of treatment with Abate. (9) An extension of larviciding to the areas studied ought therefore to be based on the alternate use of two larvicides not related to temephos; failing this, it should be arranged either to replace Abate at an early stage or to introduce seasonal alternation between Abate and another radically different product right from the start. (10) Unfortunately, despite intensive research, the only two replacement products available atpresent, although not marketed are: - Bacillus thuringiensis serotype H-L4, wtrich is remarkabl-y effective and specific, but in its present formulation can be used only at low water; - chlorphoxim (which would be the only possibility at high water in the event of resistance to temephos), despite its excessive variations in efficacy between batches and above aIl its much greater toxicity for aquatic fauna as compared with Abate. (11) In view of the definite risks which the threat of temephos resistance creates for an extension campai.gn in the areas under consideration, it is not possible under present circumstances to PrePare detailed quantitative estirrates for more than one year because the larviciding strategy for subsequent years would depend entirely on the appearance or otherwise of resistance to temephos and, if resistance should appear, on the availability and nature of replacement products for Abate. ocP/8L.2 Page 18 TABLE 1 EPIDE},IIOLOGICAL EVALUATION IN TI{E EXTENSION SIUDY AREA IN BENIN (I,larch 1979) River basins Vi I lages Census popula- tion Popula- t ion examined Preva- lence (%) Mean mf density Partial b 1 ind- nes s rate Blind- ness rate 0u6m6 basin Ou6m6 Monongo Adj iro T6w6 315 Baniguiri 390 Idadjo 392 Agbogou16 399 Mb6t6koukor-F 4O7 Hlan 4O9 Ew€ 406 Lasso-Sahoro 313 56temsi 316 W6w6 397 Djablo 393 Assio 4O8 Aguigadj i 297 365 398 295 276 314 239 351 203 223 2lL 87 220 334 384 229 260 2t5 2to 302 195 2Lt 180 75 69.2 7 4.O 70.5 79.2 67 .2 59.5 o.o 55.3 61.5 70.2 67 .3 86.3 22.8 22.L 11 .0 t7 .5 11.1 15.8 0.0 13 .6 L2.2 6.9 18. O 25.6 3.t 0.9 3.3 3.2 0.5 2.4 2.8 3.3 2.L 0.0 o.o o.o 0.3 1.3 o.6 2.3 o.9 o.6 o.o 0.6 o.3 o.o 1.6 4.o Okpara basin Okpara 398 Waria9 391 Moka 97 196 96 189 7 t.6 52.5 18 t2 5 4 o.9 0.9 2 o 7 2 Zou basin Zott Klou-Agbalo 395 Konkondji 4OO ZoutoS 414 Za-K6k6rE 4O5 Y6vi6 396 Govi 278 279 420 303)o, 256 250 295 22r 26r 72.L 7 L.6 42.9 1.1 s4.8 20.4 18.8 7.7 0.5 11.6 L.4 2' 2.4 1.7 t.7 2.3 4 o o 1 7 2 o 2 Kouffo basin Kouffo Agougan 40l Kogb6tohou69 423 Lant.a 4O4 Togo 394 Fonkpodji r64 L70 339 109 L52 161 303 88 60 43 7 53 8 2 o o L4 lo 2 2L 4 8 6 2 o.8 1.7 L.2 o.o 1 3 I 7 0 t 1 o Mono basin 402 Ahoho 403 Av6godohouE 453 259 373 239 32.3 0.8 3.7 2.O o.7 2.O o.4 0.5 Total 6 618 s 6e+ g Vi11"g." subjected to detailed evaluation. ! lncludin g 727 people examined for purposes of detailed evaluaEion. ocP/er.2 page. 19 TABIJ 2. EPIDEMIOLOGICAL EVALUATION IN THE EXTENSION STUDY AREA IN VOLTA REGION, GHANA (Mav 1978) I \rlli"g"" subjected to detailed evaluation. ! a.r"Luding 1412 people examined for purposes of d.etailed examination. River basins Vi 1 lages Census popula- tion Popula- tion examined Preva- lence (%) Mean mf density Partial blind- nes s rate Bl ind- NCSS rate Dayi basin 336 Old Dzokpe 173 Biakpd 367 Dzolu-Buen 23 Kledjo 337 Alavanyo-^ Abehonasi9 32L 418 L70 689 lL1 O 307 390 148 633 361 23.4 32.9 44.3 63.7 63.3 6 6 5 11 o 2 4 2 3.5 2.L 1.2 o.o 2.7 3.8 o.2 1.0 o.o o.4 o.7 Asukawkaw bas in 339 Menuso 377 Koto Nkwanta9 338 Atta-Koffi 376 Dodo Fie 379 Kabosso 378 Adumadum 340 Asukawkaw- Ferrye 394 391 279 394 370 34L 401 330 301 234 337 32s 306 360 66.4 68.o 65.7 81 .3 81.5 71 .4 78.2 10. 19. L2. 25. 15. 30. 9 8 3 7 7 6 t2.3 2.5 4.6 1.1 1.9 o.4 0.8 3.7 0.3 1.9 o.o 4.2 r.4 0.9 2.o Total 4 578 4 $2! ocP/8r.2 page 20 TABLE 3. EPIDEMIOLOGICAL EVALUATION IN THX EXTENSION STUDY AREA IN BRONG-AHAFO REGION, GHAI{A (January-February, l98O) River basins Vi11-ages Census popula- tion Popula- tion examined Preva- lence (%) Mean mf density Partial blind- ness rate Blind- ness rate Black Volta basin Black Volta 432 Agbolekame 115 Lt2 66.4 28.L o.9 o.7 Pru basin Pru Tanfi 424 Asubende 428 Aiyeride 427 Fialcwasa 429 Tanfiano L76 277 323 366 L62 262 290 348 77 .2 42.5 L7 .5 47 .7 34 5 5 8 3 5 4 1 3 2 o 1 3 7 7 o 6.7 o.o 1.0 0.5 Tain basin Tain Tombe Subin Bisi 437 Kyengakrom 434 Tainso 433 Wewa 435 Akete 431 Asuofiri 83 331 2L6 297 t82 75 3L2 186 28L t75 62.4 47 .9 49.9 63 .8 13 .3 t2.2 7.5 9.5 10.o 3.5 2.L 2.5 r.4 3.0 2.6 3.5 o.8 1.8 o.7 o.o Urukrilain basin Urulcwain 44O Dawadawa 438 Uruknain-Ano 260 268 225 25L 25 44 2 5 4 8 110. o.6 0.8 o.9 0.5 Sene basin 425 Seneso 299 272 37 .2 10. o o.o o.o Pumpum basin 439 Pumpumano 7L 70 6t.4 9.5 3.2 L.4 Oyoko basin 436 Yabraso 105 93 50.4 5.9 1.O o.o Mamasi basin 426 Kogbeya 78 75 5.7 7.4 2.5 o.o Arnam^a basin 43o Nsagobesa 51 39 9.2 L.4 o.o o.o Total 3 498 3 228 MO basin MA Katcha 45O Sagbadai 449 Baoulins6 ocPf 81.2 page 2L 0.9 o.o TABLE 4. EPIDEMIOLOGICAL EVALUATION IN TI{E EXTENSION AREA IN TOGO JtLy L977, March 1980 and t{ay 1981) 444 Abossomkop6 L23 239 110 20L 75 .O 28.2 Rrver bas ins Villages Census Popula- tion Popula- tion examined Preva- lence ( 7") Mean mf dens ity Part ia 1 blindness rate Blindnes s rate Mono basin Ani6 Mono Amou Ogou Aou Kra 307 Diom69 302 Kokot6 304 Onia Kop6 306 T6t6tou3 452 Akladj6nou L48 Fazao 447 Tigbada 303 Illougba O3O Konigbo- 149 Alamassou 062 ArnmoutaS 442 orsananLf Ad6da9 446 Alibi r 445 Goubi 448 Aou-Losso 305 Kokpli 346 L48 168 258 240 6L6 L25 t27 L72 264 116 208 248 168 28t 263 293 134 L4t 238 186 559 118 106 L52 220 LU 202 240 L47 268 244 77 .4 82.t 82.6 82.4 29.t 60. 1 58.8 80.1 73 .4 8s .9 47 .4 81.5 59.7 65.4 62.5 75 .8 20 34 25 11 5 10 9 25 16 31 7 28 5 2 4 4 6 6 7 6 4 5 4 2 16 .5 16.O L3.2 t6 .7 2.8 o.4 4.L 4.L 0.8 4.9 2.2 2.1 4.4 5.2 1.0 3.0 2.9 1.0 o.o 3.7 1.0 1.0 0.9 1.3 3.0 1.5 o.o 3.7 3.2 3.5 o.o 3.7 0.6 0.9 2.5 0.8 Sio basin Sio 443 cebakiu 441 Tokpo3 453 Av6dj6 247 r44 224 227 t26 2t2 86 4r 5 2 o 56 15 28 7 2 3 2 0.3 0.9 L.4 o.4 t.4 1.0 3 1 3 8 3 1 Gban Houo basin Gban Houo Domi Ov6 O14 Dayes-Djodj iq 301 0b6 3OO Zoub6ga Oga 454 378 223 4LL 309 t77 77 .2 6L.6 62.9 18 .4 6.8 4.8 2.O o.4 o.4 Asukawkaw basin Y69o€ 159 tL7 69.1 7.6 1.6 0.6 29.4 7.O 1.1 0.9 ocP/8r.2 Page 22 TABLE 4. g Vi11"g"" subjected to detaited evaluation. ! Includin g 1374 people e:<amined for purposes of detailed evaluation. EPIDEMIOLOGICAL EVALUATION IN T}IE EXTENSION AREA IN TOGO(JtLy L977, I"larch 1980 and May 1981) (continued) River bas ins Vi 1 lages Census Popula- t ion Popula- tion examined Preva- lence ( %) Mean 'mf density Part ia 1 b 1 indnes s rate B1 indnes s ' rate Haho basin Haho O58 Haho 451 Ess6-Nadj6 454 Dj6m6gni 166 Yoto-Kop6 268 333 l_o6 L7l 227 304 90 L52 40.8 L7 .6 43 .8 69.6 8.5 4.O 5.3 10. 9 t.2 L.2 o.o 0.0 o.4 0.0 L.6 0.5 Kpalim6 plateau D6v6ho 071 Kourna-Konda 237 22L 4L.O 4.o 2.2 o.o TOTAL 7 054 6 1n6L 1.2 2) /eOCP Page @@ c!N O oo Ok-) .1 *-ol**o +4 CJ F@ NQ a)@N6 or {o oo a-J r'@ il@ !o- c 6i6N or o@ +o A H z trl6 H q E Hz trl =o ts F zH &al E6l <ol -:l2rl .C cl1ld-l E ,I I ol rn xltr ol ,, hl 56t :316Zl .t) 4 a :i tr f, o6@6@ @OC cr s SI ON6 NT J@@\O60@ o\oiN@€ 600rN@660 ,l m - ooiNEdr 600 NNO ooo a d 6 6oo ocd N@€rrt@60NN6606 p B{E .o 3 * @$ o@ i 6e!N€€ @oo rN@ o50 o q,o; N@@ 60CNNO660 o dE o!dE !fi3 o 6 o il 6I' an z a! .loI 1iiD a F 'o=) dh(6 A. ,y c) a 5 o up) ( I ! I* I €@ON@o 6O ON a@ €J r@ -to ON n6 $- oo 6N -<' 'J6 qa +\t rQ NF -$ NO$N 9\a NN .t@ O Oo oa Oc ts@ON ao 6rN6 NT6+ a@ o * iOoi a+ @O oo $N Oi o-tONNN NN -oON +@ NN €a@+is' @N ad N * do o@ -$- a-ON ON ON 4\' @6 @.+ N\A 6N66 Nc) @6ON rN or .+o NO i@i 6@ ONO{ or io 6S -O @aNOO- @{ NQ io oioi@- 6Q .ta -t \til6 \toNN .+ a6 oo H+so €a\tN t \,iN ooo NN 6j O6o @io a o€ a6 @@oora NiN €o O6@i6@ $oi :o@ o4 6aOO\rO s6 66O ON@ o- E oNo 6iQ r -$oNr oro aNa@r$ $ A-\+ O$i \' r i-t@N@ o.+- N a@6NNO ooilo-t N oOO N OO6 OO6 o90 N 60-iN oo6 E NilQ a-ti HOO ooo o@-t ooo QONo@- €o6 NO$ o66Ni@ oro - o a cl$ Oro asN @aoO-i NON OFi oo@ ooo coc o60 oo * oc ooo oo oNo -t6O@@ * o3 d@o 600@o oNo -$@ C3CN_?6N@- -a C6OOon ooN NN @ @ @ NN Q@ 600 NO@ OoN z @ @ NNN * ohaoio *60 @N NN \to * hoo@ N o\to N* 6 oo oo -tN * @c +@ €6 N a o! 'o @E N@O @60NN@ ooo (A d U aro a!DAqo NO@ €60NN@606 60n r@@ lr @oo rN€600 N@@ rrt@ooNN@ o60 p @ HI ,c 16) I a)4 60iN@@ €60 NNQ ooo I ---t I I OO i I I I I ocP f8t .2 PaEe 24 TAsLE 6. No data. I{NTHLY AND ANNUAI TRA}.ISMISSION POTENIIAIS (MTP A}ID ATP) IN TI{E OUHI{E BASIN, BENI.N (Nweober 1978 - June 1981) Water- cour ae Locatlon N D J F M A M J J A S o ATP Ou6m6 L978-79 B6r.6rbrr 1979-80 1980 -8 1 94 52 298 o 92 56 o 25 o o o o o o o o o o 4 o 22 292 4l 25 64 391 t2 373 L95 1004 92 179 753 2t50 L978-79 Atchakpa 1979-8O 1980 -8 1 * 0 72 o o Ltfi o o 23 o o o o o U 0 o o 108 o o 966 382 10 151 593 778 447 o 62L 104 247 2lo7 2290 i978-79 1979 -80 1980-81 M'8616- koukou * 119 847 13 15 115 473 31 o 82 o o o o o o o o o 184 U 4 550 851 9 o 578 183 789 398 L220 609 1567 32t I 5239 Okpara 197 8-7 9 L979-80 1980-81 Kaboua * 209 323 200 38 49L 223 o o o 10 o o o o o o 456 2L 3337 193 1 o 605 L862 3128 1389 257 1060 LL67 8206 7 687 Zou AEch6 - L978-79 197 9 -80 1980-81 rlgbe * I 247 o o 23 o o o 0 0 o o o o o o o 4L5 27 4 852 t7 48 87 1034 952 t37 6 737 243 1082 28 L577 39 48 613 1 T6rou L978-79 1979 -80 1980 -81 l.larl- Maro * * 39 o 106 o o o 0 o o 30 o o 328 o o 333 o o 401 754 l1 158 699 * L242 * 908 * L4L2 12 50 50 15 86ffa L97 8-7 9 r979-80 1980 -8 1 Vossa * 185 681 38 18 244 31 o 8 o o o o o o o o o t4 o 10 1508 48 o t373 54 * 996 17 10 2093 28L 7rc 49ss 4L34 W6!16 L97 8-79 197 9 -80 1980-81 W6!€ o 8 o o o 0 U 0 o * o o * o U o o o n o o o 15 o o o o 299 t27 5 461 o 38 Agbado L978-79 L979-80 1980 -81 Save- lou * * 15 0 * o o o o o o o o U o o o o o o o o 15 o 35 5 77 I20 o 72 L47 tL2 359 Adj lro t97 8-79 1979 -80 1980-81 Banon lr * o o o o o o o o o o o o o o o o o o o U o o o o t27 5 82L OCP /8I Faf,e I ) TASLE 7 I'IONTHLY AND ANNUAI BITING RATES (MBR ltID A3R) IN VO1TA REGION AND BRONG A1IAFO B,I]GIT,N, G}LA.NA (November 1978 - June 1981) l,tsrr ! lb2 58r 56 50 64 45(\ 235 $7 188 4]4 Water- course A sr Lkawkau Location N D J F M A M J J S I i t978-79 AsulaskaE- 1979-80 Ferfi ' ic80 -8 1 t3 7s5 7 059 ') 350 )zl t74 374 5 718 3fr7 L 465 3 605 4 665 I 547 5 160 3 662 2 t89 5 797 3 820 I /+78 7 L78 5 296 2 674 6 0a) 6 356 2 557 6 ii(8 5 557 5 087 6 811 6 019 8 967 5 2lo 5 516 t97 8-7 9 1979 -80 1980 -8 1 I I 4 9@ o88 oo8 Dodofie 7 5 756 3 Bo5 1 680 LA 726 3 3t7 L 442 1 C36 r 936 371 922 899 998 2 508 2 292 660 4 782 6 27a 7 225 3 683 5 813 645 2 953 2 298 4 737 3 782 7 118 7 r28 1$L 6 053 Wesa - Gbrnhouo Ahamansu t97 8-7 9 r979 -80 1980 -8 1 10 146 5 918 10 465 9 322 1-o 500 6 485 8 191 la 726 6 123 5 569 6 011 4 501 4 817 3 087 3 001 4 853 7 436 3 548 6 181 tL @2 4 L23 4 7t8 6 364 3 255 4 664 5 299 2 73L 10 305 4 684 11 430 4 7t2 9 97t) 70 588 99 648 Djodl e t97 8-7 9 1979-80 1980 -8 1 2L L44 14 563 21 608 17 918 t7 259 25 432 21 1fr 16 734 20 003 t2 824 L7 AzL 18 193 13 315 9 773 18 848 15 143 9 390 t7 598 L7 751 12 @2 L6 a97 19 455 12 150 I 340 17 329 13 361 24 732 22 oLO 29 2t+3 21, 7 58 25 203 20 9i3 Menu Henuso L97 8 -79 197 9 -@ 1980 -8 1 | 320 675 330 3 426 2 2t7 837 1 230 2 t55 946 672 396 182 109 @3 @3 245 330 75 651 109 295 495 24{) 2lo 2t7 109 o 47 710 I20 155 574 9 270 7 375 Day r 197 8 -79 1979 -80 1980 -8 1 Hegbc 4 688 5 555 3 465 4 082 7 014 I 643 7 678 7 000 4 069 8 204 7 2rl. 1 491 5 ?74 5 859 2 387 438 710 708 2 846 2 007 1 046 2 843 2 528 548 r 465 L 935 1r8 3 614 140 983 I 2X) 1 445 41 566 47 021 t978-19 Elevagnon 1979-8O 1980-81 3 360 L3 470 6 860 8 339 to 447 4 092 6 t$2 t2 927 4 t+18 5 054 4 256 4 725 480 248 2r5 5 580 893 2 6ta 2 tfis 318 L 705 600 263 t 245 837 459 775 L 167 ), 1@ 5 430 7 058 6 386 t,5 6@ 51 864 Baa6a 797 8-79 r979 -80 1980 -8 1 Kpaa6a 815 283 845 155 620 295 5t7 109 2L5 29 o o o o 186 I6 o 294 51 o 806 87 2 32A r68 3 972 6 31I 2 684 2 875 13 024 ll 942 Pumpun t97 8 -79 1979 -80 1980-81 Klntampo Falls 594 353 t20 3ro 2rL 70 874 550 53 @5 667 248 t 27L 930 868 1 575 1 403 816 I o66 698 194 818 r95 113 831 110 115 19 53 3 lc5 109 8 218 5 248 Pru Asubende 7978-79 197 I -80 1980 -8 1 4 640 4t@ 6 227 7 57i 3 379 3 336 620 282 286 t 595 2 923 208 721 2 186 I 770 2 055 I O58 2 855 1 600 L 259 911 390 J 364 2fi7 5 580 3 422 3 7L6 2 877 3 C37 4 080 29 fig 29 689 Tanfi 1978-79 1979-80 1980 -81 Man so 490 128 785 1, 969 1 163 2 346 I 637 2 39I 2 r24 3 464 906 530 L43 870 1 930 r 699 186 473 205 1 135 915 I 346 842 572 856 837 L 710 908 1 218 | 417 L8 ?42 76 634 Tatn t91 8-19 t 9 i'9 -lto 1980 -8 1 Talaso 23 o ro9 0 I6 0 o o o 0 o 30 o 0 o o o o o o 2l o 16 o 30 (a No data o o o o o AH ho FO NO r€ GO €NiN O@ ON@o $\t 6O o9ro r@ao@n h{ ro QN+r N6oo QN NN -,Nio oo o .s6 4@ .f,i oo6N 6c){o ao €r oo O@ oo €oONNN oo o€NS rN oo @ oi\+ -t -idG $oOFNN 6rooro oo ons OoNN $N N oo oioa oo o oo N€ 6r+6N NOo6NO NO oo O€ts 6*6 6@ @o a@ o-, o* oo N{QN ro\to o6o.f, ns ilq oo c)N € N O€ @o N QN$s o* oo Fl iF6N o.inOo rFo O€i .$@i 6Fo .+Or 6qNO@6O6N ooor.af iNN rro N oo66 oaoN hOro FO\toooN N a.$@@N ooo E 6N\O@n@NtsO ON6 roN@dr N N.it A@nnon@ 600O.$ 6FNO oooo €o6 o.i N eoo\' 600 6€O o$oON€ @Hho6€ ooo o\tia@r@a aNo a\thN6N i@i r4€ -r-trhfl@i-r\, 6noo.$ o @hN460\+hN io@@o ooo :ioo€ iO-,Oa: @N€NNN ooo E O-rqoO.i\t.s o NFts €ro N NOo6NN r€o SN6 oa@\+N-+ o.$No .sNr.l'AF ooN N ooo OFOts ONr -t@ hooh9r ooo 94 Orts I/)NN NQi NNOOrr 6@OoiF oi6 Ni o60 ao6o@o NN €oo6No r96 .COo s6 \to€@oh _, ooo ooo @OiNNOdN * oNtso ooo oor F6€ r€i NNO aO.t OO€N6{i6i N oo6 O@@ @tsoo@o €-?N@Nno{@ o€osoo N i@o NOO NOO .f,€i NN * F@iQ * oo o O.t@ @i6 QNT o{N .f,4{ QNN rrN \tFts o\tO NFOi@\tNNH osts6So OOF N oooNc) ooo r-o$@o ooo z Oo@FNN d 6tsoNO@ ooN .i'N9 6FNH$O 6io ooo @oo F N €ohoNOdo@ OOF @ FOo €oo .soF oo6NNN O.f, N ooo d o u o o o F] ooH r@6 tll@60 rF@aoo >' F oh I 'd)r 'd ,y o aOi F@6ttt @ooFF@666 o q o5 oo oor F@@ rrl @60 tsFO ooo o d E6 € oor F@@lrr @60NN@ o66 o t o o ooits@@ltr@oo rts@666 o d oE 6OH FO€ rtt @oo rr@666 o !il oE 6Or r@@rtt@ooFF@660 d odil6 6 rl] 6Orts@@lrt@ooNr@ooo 6 @6 E& qoi r@ortt660Fr@ooo a E60 cd tlr ooiF@@ttt@6 0 FF@oo6 ott o! ooi F6@ ttt @60Nr@660 6 a6 oorr@o trt @ooFts@660 o o d d H o !) o o F o! 63 B ,!(3) o oIE dd B66! 3(J a ot 5do 6 o o6E a o a a P{ 5 H P{ dts t dtr ocPf8:r.2 Pl&e 26 4 () oHoIrl& o tu () zo&E A 4 2oHo trl& H Fl^Orl >616l zslHI ol ^dlaJlHbl<,1 alz6l 6l adlHIEclvol !loelJOt<>tHOIt4 zl zv 14HoA oH @ TD H E a '1 d Fr |-l z 4 e }f E4 6 }f E ts 6!q t o z * ocP f8L .z Page 27 cI Oo\' \, o@ NN €6 €ooo h€\tn @o ho o\,6O oo NOoo Qi -re6N 6@ Nc)Nr o6 d6N 9ii@ -lr €6 o6 -t -? o660 -+.$ o6 o@ONoo €h @@+a ho o@r€@o Qts *F @ N6 6O 66 a6 @o €@$\t *Noo Orocoo so o ooFN oo 6€oooi i6 Oo N@ o6 aoo6 o@Ni @€ 6o o6 \ti 4Oro N\? @6 Ooc)N c)N Q€ a@ ON iN .$o FO N€s6@a Ni\,@ o6 ro oo .S \to6 tN r\too NOo€ NN a-, 60osN.g os a€ @o \ o5 F\t ho60 ts@ €6oo ON aohN oo noON ai ON oo $i 6ooooo @o @QiNN i6 NO r@ F) h60o@n A\t 6Nr .fo .to O.s o oh@ o€ \1 60 ro@6ON \to@\,N\t o6€ ro\, oiN600 \ti @orNF@ir@ nonoNo{9i 4NO@\to :i \1 66 ONH6€\,NN OF@6oo@N6 oooN6€oOF s+@ 6CN o6@AN€ @rNoNr -1 06@$@ON€ NOi ao on6 oiN oooo ooo 600Ni$ €N oaaN\to \tr6 oNhFON o@@6@Ni .$so i{ @oo E OOo .taoN: FNO $€a NNN ooo ON@ r Ooa ooo @r6\tni@oo h o6r 6r os-t NFO rNoro@ts$@ rOF6€ €o{Ni oNoN ooo @oN@naNTN oro .+oo \,N ohoNIQ @NN ror@NO o@@ oN.$N@\'4r@ NiO Q6 a o @ * @oo\to6\,NO + -tooaoo Nr@ a 6AN oN6 a66 {d Ora NiQ$60 oid@@N@$n Orq NrO @oF -6r 6€@ oNONc) * rs @i a@o tsF\t o4\t O-*6 -toOoooN@O N6N z OOhOoh rOo o66aooooi -t.S ts oonoNO FIQ n a'.f NOn ioN N$@ O O.it * ooQ6as oo6ioo o@@ 60*@6Ni 60h@o@ orr NI c o ! 6 o oI 60itsoottt@ootsts@660 o oE I6 t CdJ 60iF@@ltt@oot-ts@ooo o q) oI 6OiF@6ttt@60 rts@oo6 E o Iu oor F@@ eooFr@ooo o !0 ts oor FO@ @ooFr@660 od N G ooitso@tt!@60 rr@666 G Gu6 Pi 60rts@@ttr@60rr@ooo o 6 a( 6Oi r@@ ltl@60 tsN@ oo6 s .vk q 6Oi r@@ttt@ooF.N@666 o D I a o € o ! a oI oIdB od oE o 5 o 6l) ) o € oo ts zHq Eo zo E I{ H zH ilE^ <rl @lQolz)t<ol ddlEll -'lH6l Hhl <61drl o !l201 H6lFfl H dto>l ol)zl<v zz a e ! Fl H 4 E 6 trI >Ia H 6! sd oz N F i@ H@ Nh 6\t\,@ Nc,ho ooNc)oo\' \, \tNNF 6r+.C \t\t@ O.$ F.f, 6 or Ni .i€ o6 o ON €o aonoN Oi F N * @ OoN ON NN .fiooNr €* .+Ots o ilo oo -, €r o rNoo Qi 6r NOo6 IN co6r€ QNOi FOi6 Oo IN NN \ta66NN tQ@o i6hN F orON io6F6N $Nsa @\t .$N o Fr ooOF 6$tsoN6 @nN€ a 66 6t i{ Oa I .So\,n a6 oo 5 @roOF@i\, oNoN€6N oo6iFN@N ts6i iN oiar\t OO.tN6 oN6 ooN iN oooo @.S N$sN\rii h60 ooo iOo ooNO\rn 6.fO NoooN N.S O ooo Noo ooo ooo ooo ()Fo\,6 ooo ooo NOO\, ooo o@o ooo O O.t ooo ooo ooo O@Fo o.Si.$ O h ooo ooo OONa ooo ooo ooo € ooo 6io F) rFoo 600 o@d NiONT ooo oo* 6nO{d * oo OtsNr@6 r@ 600ON oroQi Fooo 6NF o60 *oo o\tor$o oo* @O\tN9i z @ooa ioo roo N\tOaoo ooo *@o @noroOo oo* OOo d d !6 o o Fl 60i r@ottt ooo rr@o66 ot oE I(d dd F-l 60nN@@ rrt@ooNN@606 @ oa >z 6OrN@@rrt@60Nroooo 'U o ou ooH N@@ ttt @ooNr6660 a ou0 0 H 60i r@@ ttt @ooNr@ ooo 6 Nd 60r r@@ ttr 660 rFo o66 6 dil6 A 6Od N66 ttlooorF6ooo q 6 a6 6C)dts@@rtt@ooFroooo d vk o 60i r@@ttt@oorr@600 o !o o € o @ ! o o H o!(! B oE a o o0o ) o 5 ocP f|L .2 PaSe 28 ooo ET zHq FA z E rll E z H aH a e HdlEOI vil o dlFl 6l4alH-lHIz tlHIH@loNl aol zl o!lH Ol @!lqel HOtE>l@ otzzl<v E d z 4 4 )i >l Ezo E a; trl FlE4, H 6 !6d oz t ocPf il.2 Page 29 TABLE 11. DISTRIBUTION AND CONDITION OF RIVER DISCHARGE GAUGING STATIONS REQUIRED IN THE EXTENSION STUDY AREAS a Country Water- course Stations Ins ta I lation Calibration curves Benin (16 stations) Ou6m6Ou6m6 Ou6m6 Alpouro Alpouro I,16-I^16 Y6rou-Maro T6rou Odo 1a Adj iro Beffa Okpara Zort Zort Agbado Kouffo I Afon 86 t6rou Oues s6 Sav6 Gourou w6-w6 Bar6rou T6rou Odo 1a Banon Vossa Kaboua Dom6 Arch6rigbd Savalou Lohouta + + Delayed + + + In progress In progress Delayed In progress + + + + + + In progress + + In progress In progress + Ghana(14 stations) AsukawkawAsukawkaw Dayi Dayi Wawa Menu Bassa Bonakye Tain Tain Subin Oyoko Pru Tanfi Bridge Ferry Hotel Vakpo Amanhansu Menuso Kpaza Bonakye Tainso Asentekrom Subinso Yabraso Asubende Tanfiano To be reconstructeF To be reconstructed9 + + + + To be reconstructe# To be reconstructed9 Inaccessible + To be reconstructed Togo ( 16 stations) MonoMono Mono Mono Mono Mono Ani6 Ani6 Ogou Ogou Amou Amou Chra Dayi Gban-Houo Aou Akopakop6 Ko 1okop6 Nangbeto Tchamba Se s saro T6 t6 tou Blitta Pont CFT S irka Goubi Amou-Ob1o Glei Chra Dzob6can Brouffou Aou- Lo s so + + + + + + + + + + + + + + + + + + + In progress In progress + + + + In progress + + + + + In progress Gauge installed in 1978, since destroyed. ocP f BL .2 Page 30 TABLE 12. EXPENDITTJRE ON EXTENSION STUDISS IN BENIN, GHAM, MALI AND TOGO IN 1978-1980 AND ESTIMATED REQUIREMENTS FOR 1981, By COUNTRY 9 urti is included in project rcyf uyof ool. Country BudgeE Expenditure E s tirna ted needs 198 1L978 L97 9 1 980 Total Benin Ghana Mali Togo $ 256 4@ 466 600 230 400 229 200 $ 49 879 96 810 t4 344 63 725 $ 108 111 208 253 L22 232 113 856 $ 99 897 L73 334 73 94L 116 800 $ 2s7 894 478 397 2LO 5L7 294 38L $ 115 200 181 000 a 141 000 Total 1 182 600 224 758 552 4s9 463 972 L 24L t89 437 200 ocP f 8L .2 Page 3l U l o F z P z t!(J o :< E, U 9 z t a a l I (r TU 9 z ....+.+.+++\ tt ttt + tt (, U zt! a IJ z oN ofF](,t Y z o az lrJFx tu llo z o tr f T a J (Ji(L c,o o lrJ o i .+-++++-++l+{r =: t + t + +t{l + + + I + E oo{ o N o I a F o D att o .!!f o o o ffi \ 60 6n 3 .hI:-.io .: a r!3fut: ai] 3-eq:q.5 iN . t-\:N E UJ d) l U z =e = I i',-l! U EEU; \ I l i U lrJ z 5(, [o f I lrJU z z + + iq+t+I (, t { i + a o =o UJ Fo L) II I a I I I a a .< F o I { * t It u. ai I .I <.\I. o \. =t + a K okoo tKouborot\ i orchclrng + t I i l +t + + +{ It\ JOUGO S. l.m S qwon d a wa \\ \ \ );..Wo ri a + l I +t I +l + + +l + o lgbomo 6Krket won :: o lrEEi n o ttI , I Oiobq to o (9 o I I I + + +tt + + _- -7rfa-h d k A + +lttt Abg Mb +t I t I Fon +ti + i + t i + + + I + + Kogb UE Zaki o A ABOMEY Lo 7. CapL r uouE po bo Togo hoho Y6v i6 o A vi'9od o 6 o ALLADA o ocPfil.2 page 32 I I Nrxtfl ou3si. " . +' I I Y q a/(, FIG.2 ENDE MICITY OF ONCHOCERCIASIS IN EXTENSION STUDY ZONES IN BENIN - \t I Hypo - mesoendemicity\- Hyperendemicity Mesoendemicily H ypoendemic ity Scqle : 1 /1 500 000 0 30 50 Km ,*\i+ K U +tttitt - TEROU rguiri s30 K ok6 SAVE o Wori 9. o t ttI ,{t + godJ r oEwa Losso Soho a o SAI(ETE It a +I PORT O- NOVO I I l ++ I +tItItIIII tti lI I tI +to + 7 + II t GRAND POPO COT ON OU o t. l-l ocPfil.z Page 33 ENDEMICITY OF ONCHOCERCIASIS IN THE VOLTA REGION/GHANA Scole '. 1 /1 000 000 0 l0 20 30 40 50km Hy parendcmicity Mesoendemicity Hy pocndcmicity FtG. 3 E UMBAI A d um6dum low r to Kof { 0 XETE X cHl o Aiuko \ p b. 7 0r\ t ! t o\ K NOU o t d I tt I + + tt + +t Ch ai o f t tf I do Fr t nt6 o SIKAN Dzol ou B u I rfn t ] I od,io t Dzop. oBtok Pto . OHAVE +t + +ittt oHO I ocPfil.2 Page 34 a $ //o c .9 oroE o d s. I or c o co .; oS,Eeo EOC og .:o cO. JI z.9Iu)(9 ?E HE -o\., L L,,I tZ F,r,Ed) - LrJ lr, -oFf;z \C (9 L '-- .9 E o ! c o oo - ) :e E o! c o o lao - m p (o o2 ta I !q v g o-o oll olloll E"I :ll o]l ,qJ t' 1 ! .)! ; I lY o o l/| o o oz o o-I r o a F t o aa oo z o f' i F o alt CD ox ; z l (r l U e I i a: a > ; o a o l t o :< z z =5oU F c f o l o l! F e o , o o c .9 c o F - a o a aE c E o oo a oL I F =- o E ,A E) o- t + .5 o) I f ....-.,3 o1 \ E I f a '+i--+rrarr F ta.,ti--- t' a til/ilil I rl I I a oc? f 81 .? Page 35 ENDEMICITY OF ONCHOCERCIASIS IN EXTENSION STUDY ZONE IN TOGO Scote : 1/1 500 000 0 15 30 15 50Km ffi -:= - Hyperendcmicity == Mesoendemicity - Hypoendemicity t i I f + + NIAMTOUGOU It + l+ iI o o GUERIN U PAGoUOA @ LAHA + KARA I 4ara !t a xesou@ IIi t Boou linsi BAFITO @ r-rI t z RI ) It I U It Z trj co FIG. 5 g bodor H 9o OE i ubi OUB omc a + + gbodo BLIT tI , omko t +t no oko z (9 It A Iqm on I + + ATAKPAME o 1IIo ) +ttt +t{ ,tt +t a , I +.Gcbo L_ - ki 7c ,. 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OU o* '.+ + & I t \ ,III+ =Ev cE ta- :,Yo:3g o cno.: x!l ,[,osos o c6 oc ,a ii lrill1il ,t I 1 Fo F (, r o z o;)o g. FI o ut lrJz o N o fFa zo (n z LdFx lrJ z G, UJFa lrJ lEri lEi z€ r\I l! j *r- .x; 9 c o tL EtcOO o6i/)c n9 ac6- D JT ocPfil.2 Page 38 ,1/ N lrJ o l. +--{t +{ .l 9 o E I I t. \ I \ i-. i t oP) o \ \ \ a i +\ ,...' ( foz oFo c) lrJ -o o E,(J(J a C C o o 0oa c o o\R!rt: oEoo{t oa6a io oe! -9ei tr ooa -! E 33 'Oo> oa o I aF o v { .{ !f 2 -o 6 3 o c o : E t fs) oo stlt) c .9 I c3 x3 o = .E c 1, ,s f oo I + I + a, c o (L Q o EtTa o .= € c as a o ', ! c! E LC :.e3;t/lc o: 6: lkpri flEli a lrJ z o N o fF @ zo vt z. lrJFx lrJ z E, UJF @ lrJ ,3 =6 o o tr a 1< f, Eo: ooOi o3 rs6 (L .E F! oB a = .\ f L I oI \ t\III ( o o Fr '9,:.1 .., c o r() z -.lrl I z. o I rl I ,l I ocPfB'L.z Page 39 CE z = o cq! .!. !L3; o> a2 a- sJ os5 t, OO =.'-! a ox!a oa 0 EE !13 o , I o oo aa-,tt t a *- \t \ zI o o o v / -..+.<z o ( foz lrJ - G"(J(J J - i t I opDg -t !n o uohl oz {-o L I , o o ao \ ,++.!-a s o + : Fz .> t Ell x E';^)3;eo.: E EE a6o sc! a tuii; "EE oo-DEicc@a)t 33:" cc9i E; ^!Lrtioooti .1, Z iit!ll ': c o: ; LCooit6!-;a 1-o! + r5l lel; I <l{ lElr lrJz oN 1p (n z lrl F trJ z E UJ Fl/) trl z€ E 9 F F ; F UI otr o r slx; N + , I L d o\ uDl o + I o t t +II ..-..\ o? -f - .-'.'+-+J , =(Jz i + I ocPfil.2 Page 40 I I I +' lt .z u\ r + -.-'l +++ - +.1 \,t a.t I \ oa +e a +l IE O\ 1l I a t / I t aI\I t a I 7t.. , o a2 utF c. C' (E )o aat T E I i a!t5! ! ,\1- I +' a L a I r il a \ !t \. I l t +. + t I L -.0 ! c :E :E la 8o oZe r!: €o"5"-": D--'-8 1t Ec| oc c E E Ei i :"9 !? i :ll :i i -xll i!lotlo * I I a lrJz o N o fFo aF z. lr, =t- LuE ,- zo U) z.lrll-x lr.l zoln UJa Eo ocP f8r .2 page 41 oT I t I aF a ++ a + l I ! \ \ (tr I {lI o + a , \ Er 1, t{ ro a z. l! F E, rJ l{fo ( U a oi lrfJ a F ao o ao! b sq.r E N G t5t (, t\ I t** + I I .\ +<+++f r It +t 6 E o ID t- o .-- E cL 0, .c. fI I .E ci o,\ c o N & U o c o, a0L o. O.FOz ':g.<'o z!F)f;8(rEt-o F, 6 q.;3I ! 2r [.; t/l t lrJ z oN o Pa z o a z tr'l|-xlrl a+t a + + t a ocP f BL .z page 42 ANNEX PLANS OF LARVICIDING OPERATIONS, WITH COSTS, FOR THE EXTENSION ST1TDY AREAS OF TIIE PRoGRAMME IN BENIN, GHANA AND TOGO, t982 1. Strategy The basic principles for the larvicide applications and the entomological evaluation wouldbe the same as those that have governed the Prograrunets operations since 1975. 1.1. Insecticide applications The various larvicides would be applied in the concentrations used by the programnelfrom fixed-wing aircraft and helicopters of the same types as those used by the prograrme and equipped in the same way' in planned weekly circuits adjusted each week in the light of theentomological findings and the reports from the gauging stations. operations would be prograunned and carried out from the air base of the progrartrne,s easternzone' To avoid wasting flying hours on ferrying materials it would be wise to transfer aI1or part of the present base from Tamale (Ghana) to sokod6 (Togo). This transfer would requirethe construction of a hangar at Sokod6. The zones to be treated with insecticide are defined as follows west of Lake Volta: bounded to the north and west by the present prograunne area, tothe east by the lake itself, and to the south by the \,rater-parting between the Tain,Pru and Sene basins on the one hand, and the Bia, Tano, ofin and Afram basins on theother hand; east of Lake Volta: bounded to the north by the present Prograrune area, to the westby Lake Volta, to the east by the Nigerian frontier, to the south-west by the Dayi basininclusive, and to the south by the extreme southern limit of the breeding places of theS. damnosum complex on the Sio (6o2orN), the Haho (confluence with the yoto), the Mono(5'3o'N), the Kouffo r (6045'N) and the ou6m6 (confluence with the Zou). Larviciding operations should begin at low water, i.e. in March, so as to providesufficient time for preparation and to benefit from favourable hydrological conditions. The rivers to be treated in the dry season (March and April) would be as follows: pru(downstream), Sene (downstream), Pumpr:m, oyoko, Bassa-Bonakye, Asukawkaw, Menu, wawa, Gban Houo,Dayi, Mono (downstream), Amou, Sio (middle section), Zou and ou6m6 (dor"mstream). This would mean about 60 flying hours per month for a Hughes 5oo c helicopter; the corresponding weeklycircuits could be carried out by the heli.copter fleet currently available at Tamale, in additionto their usuaL larviciding operations within the present boundaries of the prograrmne,s eastern zone. I ,h. .orr.entrations to be applied would be as folloqrs: with Abate 2OO EC: O.O5 to 0.1 ^gftfrc min of active ingredient, depending on riverdischarge (O.15 to O.3O litres of formulation pur 12 per sec); with B.t. H-14 (SAN4O2.I.WDC)21.5 me/l/10 min of formulation (0.90 litres p.. *3 per sec, supplemented by 2O7" water); with chlorphoxim 200 EC: O.25 ngll/10 min of active ingredient (0.075 litres of formulation per m3 per sec). IocY fat .z page 43 Annex During the rainy season (May to December inclusive: 8 months) the following basins (rivers, tributaries and sub-tributaries) would need to be treated: Pru, Sene, Pumpumr Oyoko, Bassa- Bonakye, Asukawkaw, Dayi, Sio, Haho, Mono, Kouffo 1, Ou6m6. The corresponding circuits would represent 120 helicopter hours per month, supplemented from June to November inclusive (6 months) by 60 fixed-wing flying hours per month (Pilatus-Porter). The present Pilatus-Porter fleet at Tamale could carry out these rainy-season treatments in addition to those in the present eastern zone of the Progranme. The helicopter circuits would require two additional Ilughes 5OO C machines from May onwards, which should be based at Sokod6. The provision of these two aircraft would have to be negotiated witir the aerial spraying contractor, and would involve additional expenditure. The total number of larviciding ho,'rs for the year 7982 would be 1560 hours, subdivided as follows: 360 fixed-wing aircraft hours and 12OO helicopter hours, (l2O hours i.n the dry season' 960 in the rainy season, and 120 for the inspeetion of breeding places). Of these, Brong Ahafo Region would account for 300 hours. The corresponding annual fuel consumption would be 174 O0O litresl Brong Ahafo Regionts share of this would be 3O 0OO litres, In the absence of two new products that are radically different from Abate, Abate could itself be rrsed in alternation with Bacillus thuringiensis (B.t.): B.t. at low water (March to June and possibly in December), Abate from July to Novembe .-ii De..rob-.r. Consrrmptfon of Abate 2OO EC in 1982 would be 81 0OO litres, Bronlr ALrafo Region (Kintampo subsector), 12 months Berrin (Ju1y to November) Volta Region (November) Togo ( llLrvember ) The use of B.t. would require strengthening the ground-leve] facilities ment of fuel andlarvicide supplies: a team responsible for the mixtures (l a cross-country truck and a large stock of 200-1itre drums. subdivided as f ol lorrs : 7 OO0 litres 37 600 litres 15 8OO litres 20 600 litres Tota 1 81 OOO litres consumption of B.t.H-14 (formulation sAN 402.1 wDC) for the year 19g2 r"iorrld be 5o ooolitres (applicatioo" itt Benin, Ghana and Togo from March to June inclusive and in December) for the replenish- auxiliary, I driver), Annual consumption of chlorphoxim 2OO EC (possible replacement for Abate from July toNovember inclusive in Benin, Togo and Volta Region, could be estimated at one and a half timesthe consumption of Abate, i.e. about 111 ooo litres; this would be accompanied by an increase of about 102 in the flying hours and in the fuel requirements for the applications. The use of chlorphoxim is mentioned fcr information; it would not be used except in the event of proven resistance to temephos, and then only at high water and subject to prior agreement between all the parties concerned. 1.2 Entomological evaluation A network is already available (4 subsectors: Atakpam6, Togo; Hoho and Kintampo, Ghana;Parakou, Benin); this network should be maintained and an additional subsector should be opened in Lhe south of the extension area in Benin; it could be located at Bohicon; some of thepersonnel from the Porga subsector could be used to operate this new base. If this is done it would be advisable to transfer the Beninois sector headquarters to Parakor.r for logisLic reasons. JocP f 8L .2 PaBe 44 Annex It should be noted that the Kintampo subsector, which operates partly within the area currently under treatment, is included in the Prograunets regular budget for 1982. The total staff of the four other extension subsectors (three existing subsectors and one new one) would consist of 71 general service staff. The following items would be required as basic equipment for the new subsector: 2 cross- country vehicles, 1 light vehicle, I binocular microscope, 1 refrigerator, 1 freezer, 1 air conditioner, 1 generator, 1 radio antenna and 1 transceiver. The vehicle fleet for the extension subsectors would consist of 16 vehicles. The monitoring methods (insect collection, dissection, inspection of breeding places) would be identical with those used during the pre-larviciding period. A special effort should be made in the villages that were subjected to detailed medical evaluation in the pre-larviciding period. 1.3 Medical evaluation This would be the task of the specialized unit of the Progranrme; the protocol would be the same as in the areas already under treatment. No folIow-up investigations would be necessary in 1982, but it would be useful to carry out a few detailed evaluations in some areas that have not been thoroughly studied (Benin, Volta Region) and in the villages where the pre- larviciding entomological data are particularly plentiful and interesting. 1.4 Aquatic monitoring This would be carried out by the specialist national teams of the three countries concerned, financed and supervised by the Progranrne under bilateral contractual agreements on the same basis as those for 1981. 1.5 Miscellaneous The larviciding treatments in the extension study areas in 1982 would necessarily be largely experimental. They should be utilized to obtain the maximum additional information on the following points: measurements of river discharge (improvements to the networks of the three count.ries through contractual agreements with the national hydrology services); mapping of Volta Region (signing of a contract for overflight, aerial photography and compilation of maps on a scale of 1:2OO O00); practical details regarding the use of B.t. (proportions, methods of application, prior dilution, etc. ); improvement of treatment methods in mountainous areas; additional study of reinvasion in Northern Togo and Beninl a study of the impact of the extensions on larviciding operations in the present OCP area. J' ocP feL ,2 page 45 Annex 1.6 Beplaqement slralegies If resistance to temephos shouid appear before the end of 1981 (or for practical purposes before the 1982 budget is decided on), the strategy should be modified as follows: - application of Abate in Brong Ahafo Region (Kintampo subsector), B.t. applications at low water (March to June inclusive and December), entomological evaluation, aquatie monitoring, aod the hydrological and cartographic work would all remain unchanged; the applications of Abate (Ju1y to November) would be cancelled and replaced either by applications of chlorphoxim (subject to the express agreement of the JPC) or by an intensive programne of comparative trials of new insecticides and new formulations under operational conditions, which would mean that only one of the two additional helicopters would be needed; similarly, if resistance should appear during the second half of 1982, the applications of Abate would have to be halted inrnediately. !ocef ar.z page 46 Annex EXTENSION BUDGET 1982 (in us $) Ihe costs Per sonne 1 estimated for 1982 are as follows For General Service posts within the Progrartrne area the average annual costs are $ 4OOO. Aerial operations Hourly costs are based upon contractual terms of $ 385 per aircraft plus fuel costs of $ Sg. Insecticide: These are estimated to cost (including sea freight) : - Abate - Chlorphoxim - B. r.H-14 Vehicles: Average cost per vehicle is estimated at $ 13 230. Exchange rates per US dollar adopted for calculations are as follows 7 .80 7 .40 5.20 $ $ $ FFR CFA DM L982 (Abate and B.r.H-14) L982 (Chlorphoxim and B.t.H-14) L982 (-B._!..H- 14 and new insecticide) ANNUAL COSTS Per sonne 1 Aerial operations Insecticide Contracts Operational travel Supplies, acconrnodation, uti Iities Operations and maintenance 292 000 780 600 943 800 93 000 62 200 54 000 100 000 292 000 825 000 1 126 000 93 000 62 200 54 000 100 000 292 000 310 400 362 000 93 000 62 200 54 000 100 000 Total 2 325 600 2 552 200 L 273 600 CAPITAL ITM,IS Buildings Furniture Vehicles Technical equipment 100 000 5 000 52 900 12 500 100 000 5 000 52 900 12 500 5 000 52 900 12 500 Total L70 400 170 400 70 400 Grand total 2 496 000 2 722 600 1 344 000 a 5.65 283 2.39.