().ch.ccrcrasis control prograrnrne in tlre v'lta Iliver Basin area I)rogranrnrc dc I-rrltc contre t'onchocercosc dans Ia Itdgion tlu Bassrn cie la Volta
J ( ) 1 N',t' t)R.( )c; I{A Nt I\,1 E C( )ilt M I.l"l'tiu
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JPC-CCP
COMI'TE CONJOINT DU PROCRAMME Ilureau du PrdsidcntJPC3 .5
OR]GINAT,: FRENCH
0ctober 1 982
JOINT PROGRA}{ME COI'O{ITTEE
Third session
Bamako 7-10 December 1982
Provisional Agenda item 8
The report on the additional studies in rhe Southern extension zone (Benin-Ghana-Togo) was revj-ewed by the Committee of Sponsoring Agencies (CSA) and is now transmitred for che
consideration of the Joint Programme Connnittee (JPC) at its rhird session.
The CSA, recalling tliat operational activities in this Southern extension zone were
being thwarted through the want of two operational back-up lar.zicides as required by the
Ecological Group' considered it mandatory that the main infrastructure be maintained
in the area to protect the investment already made. The funds required for this purpose
are shown in the addendum to the Plan of Action and Budget for 1983. 1r recommends
that the limited activities to control reinvasion from source rivers in the area as
proposed by the Expert Advisory Committee (EAC) (Document JPC3.3) be undertaken.
a
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WORLD HEALTH ORGANIZATION
ORGANISATION MONDIALE DE LA SANTE
ocP82.2
ORIGINAL FRENCH
I
ONCHOCERCIASIS CONTROL PROGRAMME
IN THE VOLTA RIVER BASIN AREA
ADDITIOI.IAL STTJDIES IN THE SOUTIIERN E)CIENSION ZONE (BENIN-GIIANA-TOGO)
1. Background
The final report concerning the Programme extension studies in Benin, Ghana and Togo (JPC 2.7) was submitted by WHO in 1981.
The report clearly showed that onchocerciasis was as serious in these regions as in the more northerly adjacent treated foci, and that it was similarly amenable to vector control by
larvic id ing .
Although the entomological data were regarded as adequate for the planning, costing, carrying out and evaluation of larviciding, it was emphasized that there were some gaps in the reference data: the mapping of the river neEwork, the setting up and calibration of gauging stations, and the collection of hydrobiological data prior to treatment.
Lastly, and above all, the report emphasized the presence of the species S. sanctipauli and S. soubrense almost throughout the area covered by the extension studies; in the wesEern
part of the Programme area these species had exhibited resistance to organophosphorus
insecticides following a few months' exposure to certaj.n of them.
The final consensus at the meeting of the JPC in December 1981 was that it was not very r^/ise to undertake systematic larviciding in extension zones populated by forest species of the
S. damnosum complex as long as there was no larvicide suitable for use in all seasons apart from the existing formulation of B.t. H-14
This document is therefore an attempEed updating of JPC 2.7; stress wilL be laid more particularly on what has been done to fill the gaps whose existence was emphasized in that report and to respond to the recommendations of the JPC.
2. Entomological evaluation
So as to allow for the southeasterly shift of evaluation activities, the Benin sector has been transferred from Natitingou to Parakou and a new sub-sector has been opened at Bohicon
to replace Lhat at Porga. The staff have been kept on and the vacancies for sub-sector chief technicians are being filled in Benin and Togo.
The collection of data on biting rates (MBR and ABR) and on transmission potential (MIP
and ATP) has been continued at the 70 or so selected entomological monitoring points that are
regularly covered (see Table 1).
Consultants have elucidated the morphological characters for identification of forest
sPecies of the S. damnosum c
I
east of the Prograurne area.omplex, which it is especially difficult to exami-ne in the south-
oeP82.2 Page 2
3. AeriaL operations
Preparations are in hand for the transfer of the aerial operations base of the eastern zone from Tamal6 to Sarakawa (Togo), a move partly prompted by recentring of the larviciding circuits in anticipati-on of the southern extensions.
4, Study of the role of S. soubrense and S. sanctipauli as vectors
Consultants have been at work on the subject since the 1981 rainy season, deEermining the
maximum northward extension of these species season by season, Eheir vector capacities and their contribution to transmission by place and by season. The first results suggest that the representation of these species is relatively poor in the northern part of the extension zone, and that the rates of infestation by O. volvulus decrease from south to north, while the parasite load increases, but it is still not possible to deduce from this the impact on annual Eransmissi-on dynamics; the same studies have therefore been resumed this year to complete the
data obtained in 1981.
One of the most tangible consequences of the experimental larviciding carried out during the rainy season in 1981 in the upper, basins of the Asukawkaw (Volta Region) and the Mono
(Togo), under suspicion as sources of reinvasion, was the very long period that elapsed
following larviciding before these breeding places were repopulated. What is no less interesting is that this delayed repopulation was by S. squamosum, replacing the original
Populations of S. sanctipauli and S. soubrense, which did not tend Lo regain their dominant
status unEil the return of the rains in 1982
5. Aquatic monitoring
The Progranrne has recruited a hydrobiologist and a hydrobiological technician who
coordinate and supervise the national teams and themselves carry out monitoring where these teams are sti1l not operational.
A $ 2L 750 contract has been concluded in Benin with the Cotonou Fisheries Board for invertebrate monitoring, and two dry season missions, the results of which are ar{aited, have
already been carried out at t\^7o stations. Three ichthyological missions have been carried out at six stations by the Programme hydrobiologist (December, April and July-August); a trainee ichthyologist from Benin is receiving practical training.
In Togo, a $ 7470 contract had been concluded with the University of Benin in Lom6 for invertebrate monitoring, but only one survey was made in December I98I, and the results were
not communicated; data on invertebrates are, therefore, now collected by the hydrobiological
team of the Prograrmne. Three icthyological missions have been carried out by this same team
at four stations (December, April, July); an ichLhyological trainee from Togo took part in the last two missions,
Ttte collection of entomological and ichthyological data is being continued at the
established rhythm in these two countries in 1982 so as to gather the greatest possible amount
of faunistic data prior to treatment.
In Ghana, teams from the lnstitute of Aquatic Biology in Achimota have continued their monitoring of t.he entomofauna and ichthyofauna, as in the past, under the contractual agreement reached with the Prograrmne, which has been renewed annually since the start of the Programme
($ 30 600 in 1982 for the monitoring of the whole of the Programme area in Ghana).
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ocP82.2 Page 3
6. Improvement of the network of gauging stations
ReaI progress has been made in Benin, where ORSTOI'1 has installed and calibrated six additional water gauges in the Ou6me basin under a tripartite agreement, with the logistic support of the programme; an extension of this agreement for the calibration at high-water levels at three of these stations is currently under neSotiation.
Additional measurements of discharges and recalibrations of gauges have also been under- taken in the Mono basin in Togo, and others are planned for 1982.
Lastly, the programme has given its logistic support to the hydrological teams of Ghana
for Ehe installation and reconditioning of gauging stations in the Volta Region and the Brong-Ahafo Region; it is envisaged that this support will be continued for the calibration of these stations.
7. Carto aphy
Under an agreement reached with the Programme, the Geographical Institute at OuagadouSou
has carried out a considerable amount of work, and the Programme will shortly have reliable
1:2OO OOO monochrome maps of the mountainous regions of the southern extension zone.
8. Reinvasion studies
The experimental larviciding using Abate planned for the end of the dry season and the beginning of the rainy season in 1982 in assumed sources of reinvasion was cancelled so as noE to risk the premature triggering of resistance to organophosphorus insecticides.
AII that was done was to carry out a sustained study of the dynamics of this reinvasion by means of a strengthened catching and dissecting network in the basins of the Mono and the
Ou6me with the assistance of consultants.
9. Studies of susceptibilitv to insecticides
Susceptibility tests on a wide range of insecticides have been carried out regularly for about a year by specialized Programme teams and by a Ghanaian team of the Volta River
Authority under a contracLual agreement reached with OCP. For the moment, all the vector species of che southern extension zone seem to be susceptible to all the insecticides tested, although the forest species Ehat are known Eo be liable to develop resistance to organo- phosphorus compounds rapidly occur widely Ehere.
10. Larvicide screen]-ng
The insecticide research team of the Programme (three research workers and two technicians when at full strength) has been based at Kara, where a screening laboraEory has been set up.
Several formulations and new compounds have already been tested at various stages.
Previously, at the end of 1981, the lower Mono was the site of comparative trials of several of the customaryinseclicides (Abate, chlorphoxim, B.t. H-14) released from a helicoPter.
11. Conclusions and prospects
The knowledge acquired through the Prograrune has been appreciably enriched in the sPace
of one year with respect to pre-control data on the dynamics of Eransmission, Ehe role of S. soubrense and S. sanctipauli as vectors, the susceptibility of the vector species Eo insecticides, the mapping of the river network, development of the gauging station network, and inventories of Che non-target aquatic fauna. Having regard to the experience gained within the area currently treated under the Programne, this knowledge should be sufficient for the conrnencement of systematic larviciding.
ocP82.2 Page 4
Nevertheless, this cannot be envisaged at the present staBe, in view of product that could be substituted for Abate under all hydrological conditions
res is tance develop .
the lack of a
should temephos
I
The lack of such a substitute has prevented systematic larviciding of assumed sources of reinvasion this year, although only such treatment could provide rn
""r".".ent of the impact of the extension on the protection of the centre and east of the progrannne zone,
Proposed Research for 1983
In accordance with the reconrnendations of the Expert Advisory Ct'rmmittee in paragraph 82
of its rePort (reference JPC3.3) it is proposed that Teknar be used for a period of four months from May to August 1983 in certain rivers of the area as a means of reducing the possibility of reinvasion of the central OCP area.
Ttre budgetary requirements to recover this activity in addition to what is presented in
document JPc3.9 for maintenance of the Southern extension infrastructure, on-going activities
and services will be uS $2oo ooo, to cover the cost of aerial operations, insecticides and
short-term consultantshios .
ocP82.2 Page 5 TABLE I. ANNUAL BITING RATES AND ANNUAL IBANSMISSION POTENTIALS
AT A NIJ]'{BER OF CATCHING STATIONS IN THE SOUTHERN E)ffENSION ZONE
I I
I
I
L97 8- L97 9 1979-1980 r980-1981
watercourse S tat.i on
ABR ATP ABR ATP ABR ATP
Asukawkaw
Wawa-Gbanhouo
Ani6
Ogou ou6mi
Amou 0kpara Zot T6rou Beffa
W6w6
Agbado Adj iro
Menu Dayi
Bassa Pumpum
Pru Tanfi Tain
Mono
BeEerou Atchakpa MbeEekoukou Kaboua Atcherigbe Wari Maro Vos sa W6w6
Savalou Banon
Asukawkaw-Ferry Dodofie
Ahamansu Dj odj e I'lenus o I.legbe Elevagnon Kpasa
KinEampo Falls
Asubende Manso Tainso Landa-Mono Kpes s i Atchinedj i Tetetou Fazao Paga la Alamansou Sirka
Amou-Ob1o
39 886
4t 669
tL2 9L7
r30 424
49 4L5 47 327
L46 276
27 765
7 Lt4 12 728 76 340 56 782 70 588 235 807
9 270
4r s65
45 660 L3 024
8 218
20 509 L8 242 30
52 340 45 066 55 387
Loz 659
36 646
2t 322
64 7L6 14 3ll
26 439
753
2 Lo7
3 zlL 8 206 3 948
L 250
4 955
I 275
LL2 (o)
7 775 9 763
tl 016
14 389
L 92L 3 513
667 705 46s
2 632
t 145 o
L zLL
2 349 2 552
4 929 324
L 449
7 855 831
L o42
64 4so 50 581
99 648 L88 434
7 375 47 02t 57 864 LL 942
5 248 29 689 L6 634 60
37 843 58 006 58 385
93 604
t8 781
9 970 57 78I 14 851
39 465 )(J 38 37 103 46 IU 81
I8
8
L4 328 187
23t
313 542 476 324 141 819 L28
5 015
4 L34
821 359 (0)
6 800 9 3L7
LL 622 L4 782
I o55
6 106 598
L o44 L77
2 205
2 025 0
I 588
3 s84 3 070 14 oo3 572 844
4 433
1 139
3 961 150
2 290 5 239 7 687
6 131
20 863 L7 L56
s9 698
6t 572
20 5L6
23 776
34 772
4 898 3 903
L8 2L6
Lt 874
44 67L L5L 952
3 298
t8 448
5 452 2 767
26 34L L8 749 232
17 683
23 226
3t 946
174 8oo
6 LL7
3 245 34 356 (632) 32 228
438 329
4 L7t
I 958
L 120 454 T 3L4
L7
100
760
15
2 386
t 710
o 677
1 067
I o35 13 489 25L 146
2 959 (o) 3 006
2 386
2 434 5 443 Lo 448 396
2 923
