I oucnocpRcrAsrs colrrRor,

'T-

I

oucnocpRcrAsrs colrrRor, ^pRoGRAMME

IN

^{TTIE VOLTA} RIVER BASIN AREA

SCTE}MIFIC A}TD TECHNICAL ADVISORY COMMITTEE

Seventh meeting

Brazzaville,

21-25 Aueust 1978

ocPlsTAc7.2

ORTGINAL: ENGI.,ISH

OCP EVALUATION REPORT

Revlsed version

(,lury

_rgZB)

a o

4vJ -i2-an-

Chapter

I

Chapter

II

^:

Chapter V

Chapter

III : Ihe Control

Campaign and

lts

Results

Chapter IV

EVALUATION REPORT

COI{TENIS

History of the

Programme and Management Structures

The Problem

of

Onchocerciasis and

the

Objectlves

of the

^OCP

Research, DrvLronmental

Protection

and Tralning Implementatlon and costs

PIan

of Actlon

and Budget 1980-1985

IJST OF

ILTUSTRATIONS

Programme area as

of I

January, ^L97B

Management structures

Chapter

II : Dlstribution of

species

of

S.damnosum complex Age

dlstributlon of bllnd in

¹⁵

^villages

Chapter

IfI

^:

Aircraft

treatment

circuits

Refuelllng points in the

Progranrne area Annual Transmlssion

Potentials -

^L977

Annual

Bitlng

Rates

-

^L977

Annual Transmisslon

Potentials -

Pre-cont,rol Annual

Biting

^Rates

-

Pre-control

Areas

of relnvaslon,

catchlng

statlons

and experlmentally

treated rivers

Mean

dally catches'of

S.damnosum

at

relnvaded

sltes

Technlques

of relnvaslon

study Reinvasion areas

ftrdemicity of

onchocerclasis

in the

Programme area Geographical

distrlbution of

blindness Ln Upper Volta Population

dlstrlbutlon -

^Upper

^Vofta

¹⁹⁷⁵

Chapter

IV :

Aquatic monitoring

sltes

Chapt,er

f

E\TAUIATTON REPORT

Provlsional List of

^Arurexes

Annex

I

Annex

II

Annex

III

Annex fV Annex V Annex Vl

lNot

"r""ently ^included in this

^version

I

Chemotherapy

Aerlal

Contract Reinvaslon

Epidemlological Evaluation data Research

Training

CEÀPIE|

I

EISIORT OF

ffiE

ItsOGBATT..IE

AI'ID MANÂGEmJT §mUCîUnXS

1.

Oachocerclasle,

or rtver bllndness, ls transrnttteit ln

^Wgsl

Africa

by

blaclÉIles,

belonging

to the

SlEgùirrn ttannosun complex, whieh breed,

in rapid§ flowtng

Eectlons

of

xoany

rlvens. ^tIriE

dleeaae,

rhlch ls partlcularly

aeÿere

in the

Srrdan and Gui^nea savalra zones, 61rngB

wlth it itebilitatlon

^and

bIt:dnesa. In parts of the l[eet African

_sarranna onchocerclasls

constitutee

an

i-nportant

detement to

^hrrnan settlement amd,

the

subsequent eeonontc d,evelopment

of

rany

valleys

which

Ile

nnhhabited, and rrnproductlve.

2. In

1974,

at the

begtnning

of the

Olehocerciasie

Control

P1:ograme ^(OCf) corertrtg

nearly

_7001000 squ€Be

kilorneters lr the Volta Rlver basinl lt

was

est{mated

thât

LO3

of the

populatton was barbourlng Grchocerca

volvrrlus.

the

paraelte

causlng onchocerciasis, and

that

about 70r0OO people were

bIlntt

as

a

consequence

of the disease. It is not possible to

asBess

the

exaot nunber

of bllnd, tn the hograme

atrea,

but lt

^{1s more}

reLerant to take irrto

coasideratlon the

geographical oonceatratlon

of

bLlndness due

to

onchocerclaElE

ia certaln

atreas, when

estlmaltng ttæ

^rrnFact

of the dlsease. ^the epldenlological pattern of ocular

onchocercS.aslsl

w'ith

extreme§ ^hrgh bllndnese

rates

Ln

relatlvely

^young age-groups

ln

emall

nral

populatLonal

explalns the

^{nportant

soelo-econonie consequenee

of the

diaease.

3.

^Awareaess

of the extent of the

problern ^had been

steadlly

d.eveLoplng

sfuce

the

L94Os.

Systenatlc

srrmeys

to

^aesess

the

rcagaitutle

of the

_trnoblen and

studles to

ilevelop and evalute

potentlal control

measures were careied

out ln

^nanÿ

of the corrntrles

concerned.

since the ear§

195Osr

ttlrs

^providing

I

pa€e 2

I-q»rovetl background,

lnfornatlon

on

the

epld.enlology and, eoclo-economlc lnportance

of the d,i§ease. Control

operatlons sfm{ng

at the

d,estructlon

of the vector

were

camietl out durlng the

1960s, begir:nlng on

a

mod,est scale and ctrLnlnatlng

la

a samFalgn

lnvolvlng _three

cor.mtæles

ard

6010O0 squar.g

klLoneters,

under

the

aegls

of the

Governnents

of lvory

Coastr

I'lqll

_{and llpper}

ÿolta

1n associatlon

wlth

tJre

E\ropean Developroent

hrnd (nof),

_and,

_the

Organlsatloa de Coordrnation

et

^d,e

coopération pour

la lutte contre res

Grand,es Ebaénies (occoE).

4. ^In I96e the

^Yor1d Health Organiaatfon (WnO),

ln jolnt

sponsonshlp

with the Unlted

States Agency

for Intærnatlonal

Development (USAfp),

*d

^OCCGE,

convened

a technlcal

conference

in t\mis to

^conslcter

the

problem

of

onchocerclasls.

llhe conferenee concluded

tirat control

by rteans

of larnlcidlng

nas

teclrnically

feasLble and chances

of

success would be

greatest lf the

operati.ons were car.rled

out in

ecologicaL zones

Eufflclent§ large to obvlate the

aeed,

for

contLnuous

eontrol of the

whole area

in

ord,er

to ^protect it against reinvasion by

the onchocerclasls

vectore. It

^wae recomended,

that prlorlty

be

glven to

^larrnchlng

a large-scale control

programe

ln the ÿoIta

RLver

basla

atrea,

lmrolvlng adjohrng parts of ^Benin,

Ghana,

Ivory

Coaetl

Uallr tri6er1 logo

and. Uppe:r

Volta; to ^protect

populattona

Eerere§ affected _{by the}

_{ilisease and}

to coastltute

tÀe cornen-stona

of future

coordinated

action against

onohocero!.asLs, andt

ln favour of

assoclated.

d,evelopnent,

in Africa

eoutb

of the

Sahara.

5. ^In

¹⁹⁶⁹

a

meeting was organizect j.n BrazzavlLle

by the

^ï?H0 Reg5.onal

Office

for Africa to refiae

fr.rrtir.er

the

approach need.ed

for

^preparing

the

proposed carnpaign.

n?erts _{fron üre}

Governnent

of

^{Ghana, OCCGE} and IISAID, Ln

addition

to

^IrHO

representativesl

attended these d,lscussionso

Shortly thereafter,

1n 1969 and 1970r

several of the

lnterestecl

cor:ntrles subnltted

formaL requests

-

Cbapter

I

page

,

eaanattng

frm the highest authorltles - ^to lnternatlonal

and.

blLateral

source§

of ^technlcal

cooperatlon and trnd.in8 which were thor.rght

to be

lnterested,

ln

contæibuting

to

sueh an a;abitious

untl.ertaklng.

^Aroorrg those organlzattons were,

the

^{trrootl an(t}

Agrlcultr:re

OrganizatLon

of the

Uuited NatlonE ^(nAO),

the Interna- tLonal

^Bank

for

Reconstruction ancl Development

(maO), the

^USAID and ^wI{O.

Si-m.rltaneouely,

the

United l{atùons Developroent hogra':me ^(U,mp) rnanlfest6d

lte interest ln

broadeptng

i-ts oclsting lrnrolvenent in

onchocerclasls

stutlles

and

control ln the ÿolta Rlver

basin âtrêâo

llheJrreparatorv phase

6.

^0a

the

baEis

of the

requests recelved. antl.

at the

srr6gestion

of

^I3RD,

l[80 and ^UNDP sponsored,

a neetlng of

lnterestecL

partles in

^Geneva

ln

^19?O to draw up

the

tellms

of reference of

a mlsslon d.esigned

to camy out

complementary

inveetlgatlons ln ^the

seven

countries

concerned, as weIJ.

as to plan

and cost

the

proposed Onchocerciasis

Control hogra:mre. Ihls heparatory

^Assistance

to

Governnents (pÂe)

nisslon

was funded

by

^t7liDP

with

^FAO as ÀEsociate Agency.

7. li[eaurhile, in

19?2,

the

Direetor-General

of

^FAO,

the

Presldent

of BD,

the Adnlntstrator of

^IINDP and

the

Dlrector-GeneraL

of ^IïII0, ln vien of

the

tmFortance and

coryLerity of the

seheme emrisagecl, decldetl

to set

up

a

^Sf,ssrrng

Comolttee, comprlslng

a representative of

eaeh

of the forrr

sponsorirng agenclesl

to

ensure

the

coord{nation

of the action

taken by these ageacles i.re

the

^p].annJng

andl Lnplenentation

of the

hograrrme.

qhepterl

page 4

8. $re finilings of the

^PAG L&ssioa and,

the ilata or§lnat{ng fton

^other

prelrn{nat'y investlgatlons

were conblned

to

^form

a reportl,

^{whlch wae presented}

ilurlng

1973

to the

Gorernrnents

of

^{Beninr Ghana,}

Ivory

Coaetr

ltrall, llIger,

[ogo antl Upper

Volta. thls report

fomtrLatett

a plan of

work

for

onchocerclaslE

eontrol ln the ÿolta Rlver basir

area whlch could

lead to the

repopulatlon,

settlenent

ancl economic d,evelopment

of the

end,enlc

zones. Ihe report

was also presented

to various

agenclesl

instiürtlons

and gorernnent.

9. ^[he

^Plan

^of

Operatlons proposect

by the

^PAG }lJ.selon

report

vag endorEed d,uring

the

conference heLd

at

^Accra 1n l{ovenber L975 wtrlch brought

together

the Eeven GovernnentE involved,, and. tÀe

forrr

sponsorlng

agencles. At tbe

conference

the Agreenent

governlng

the

operations

of the

Prq3rasme (Operationel _Agreenent)

wa§ f612g11y signed.

by the partlclpatrng

Governments

artl t7I{0.

[h1s Agreement,

which

set out the baslc

arrangenents

for the

nanagement

of the

hogra"me, waE

supplemented

ln

1974

by lndivlctual

Corntry

hotoeoLs deflning the speclflc eontrlbutions of

each Governnent..

10.

^As

&ecutrng

Agency, ffiO was assigned

the task of

lmplementing the hogra[me whlch rvas

fortrâI1y

establishett

fron ].

January 19?4

with

fieadquarters

ln

Ouagadougou, Upper

ÿolta. Ihe flrst ^year of acttvity

was devoted

to settirg

up

the etrrrctures, the recrultment

and

tralnlng of staff, the

dernelopnent

of lnfrastructtuer the

purchase

of

^{equlpnent and,}

supplles,

compLenentary sur"v'eys

and

the lntenslficati.on or resea,rcb.

Actt:a1

control

operatlons began i-a

February

L97j.

1

'

^{UI,IDP, FAO,} IBRD and ^ttEO

(19?r)

Onchocerclasis controL

ln the

^Vo1ta

River

basln

area. ^ReElrt of

ttre

heuaratorv

Assistance ld1ssion

to the

Goverrurcnts

of

Dahomev.

Ivory

Coast.

Mali.

+

^Ànnexes

0-1 to -fI-5.

_{24OO co.}

^iÂer.

^{lloeo and llooer}

Volta æPhr.L

-

Gtrapter

I

PE€E ⁵

IL. ^îhe

^nachlnery

establlshed

to'oanage

the

Progracme lnclualed,

at

the corrntry

leveI, Natlonal

Coroalttees

for

Qlchocerclasls ^(ttOC), conprlslng representatlYes

of the

maln

national

se:rrices concerned,. ^The roLe

of

these

eor,mi

tteea ie prlnclpallyr to

coord,lnate

the actlon of all ^national

^gersrlces

involved ln the

Progrnrrne and.

the

subsequent econolalc developnent proJects, and

to

enaure

Liaison

betrveen

the

Goverrurent and, Progrerims f,64dqr:alters.

L2. At the

a€ency

leveI, a Scientiflc

Advlsory PaneL (Snp), _arnile up

of

nearJ.y 2O0

technical

and

sclentific

workers, was forrued by tIHO

to

^be

called

upon,

as

necessary,

for

^advice on

all

aspects

of the

dlsease and.

its control.

Lr.

^An

Ecologlcal

Panef

(æ), conprising a

small group

of

experts

wlth

wlde experlenee

ln river basin

ecology,

the

epidemiology

of

dlseases 1n

river

basins and

tire ecolo.;icaI effects of

pestiei.d.es, rzas

set

up

by the

Steerrng Comlttee

to

^guarantee

satlsfactory protection of the

enrrlronnent.

14. At tne Parls neeting of

donor and

partlcipating

Governments and eponsorlng agencles,

in

June L974,

it

^was agreed

to anpllfy the

managenent

shuctures of

the

hogran:ne. îhe atldltional

stæuctr.rres lneludect,

ln partlcularr a Jolnt

coortlinating Comai.ttee (lCC

)

^composed

of representatlves of ttre

seven

corrntrles, all

contrlbuttng partles

and. üre

four

agerrcleel.

lhe role of the

^JCC was

to

exercice general supe::vielon

over the policies to

^be ad.opted 1n

the

^planning and executloa

of the

Progranme anil

to follow the

development

of activitles. fhe Comlttee,

wh:tch nould, be presld,ed

other

by an Independent Chalrsran and served by

a jolnt

vHo/r?orrd Bank

secretariat,

would meet once

a

year

for thlE

purpose.

15. [o ^provitle the

JCC

with a

continuous independeat

evaluation of the

teehnlcal aspects

of the

Programne, ïIEO formed

a Sclentlfic

and Sechnlcal

Advisory

Cormrtttee

(SÎAC) _composed

of

^{12 menbers}

of the Sclentiflc

Advisory

Panel. îiris

Cor"m'lttee

would

neet tnice a year to

revlew

seientific

^and

tecbnleal

aspects

of the

hogranme'

and.

to

prepare an annuaL

report contalnlng lts findings

and reco:orendattons

for

subnisslon

to the

^JCC through ViiO and,

the

Sf,qsr.ing

Comittee.

Belglum, Beninr Canad.a, trhance, Fecleral Republic

of

^{GernanJr, Ghana,}

Ivory

Coast;

Japan, Kuwalt,

l/lalir

lüetherlands,

I{iger,

Ilonvay,

logo,

Unlted Kingdon

of

^Great

Britaln

ànd

Ilorthern lreland,

United StateE

of ^Anerlca,

^Upper

lolta, the Aftica

Developaevll

Ban$ the

Un1ted

i{ations

Developnent Programs

(Umf), _the

Food _and Agricultr.rre

hganlzatlon of the

United.

Natlons (U,o), _the

rÿor14 ganrr (IBRD) _ana

the

^iT6316 Eealth Organization.

L

CbaPter

I

page 6

L6. Flnallyl the

^Steertng

Comittee

eetablished aa Econonic Developaent A(lvlsory Pane1 (fOÂP)

to

^assure

the

contlnuous

revlew of lnfornatlon relating to ^the

^economic

developraent aspects

of the hograme. this

^Panel, composed,

of

economlsts and spe-

ciallsts la agricultrlral

^and,

n:ra1

cleveloproent would meet

twice a

^year and would present an annual

report

on

its flndings

and recormendatlons

to ^the

^{JCC through}

the

Sank and

the

Steerlng Comdttee.

17.

^[hese

addltlonal

EEtrctrrres were êescribed

in a

ldenorandum

of

Understanttlng whlch was approred

by the

^JCC

at lts first

session 1n AbidJan,

Ivory Coastl

1n

Febnrar;r L9?r.

I8.

^Followlng

the

assurances recelved, from

contributlng partles at thle first

session

of the

JCC, an 0nchocerciasiE hrnit A$eement coverlng

the flnanclng of the first si*

^years

of

operations rvas slgned, on ? ^Lxay 1975 by

ni.nel

^donor

Governments,

the Aftlean

Dgys]epnent Baxk,

the

IBRD, IDA, IIUDP and ^[rHO.

19. In

1976r

following the consolldation of the

hogranme

activlties in

^the

field,

and

wlthin the context of tire

^new

orientatlon

belng

glven to the firnctlons

of the

Organixation as

a whole, the

decision was taken

by the

Djrector-General

to hansfer the responsibillty for tbe

Progra,nme fuom ^lÿHO Headquarters

to

the Regional

Offlce for

^Afr

ica. llhis transfer

lnpJ.led both

a

new approach

to

Tnâna€ement and

a reorganiaation of the

supporting

seryices. îhusl

1n ^Decerober L976,

a

^new DL:rector was apolnted and

the

Headqr.urters

in

Oragailougou assrrmed

fuII responsibillty for the

lmplernentatlon

of the

hogramme under

the authority

of the

^lfEO Regional

Director for Afri.ca. îhe Offlce of the hogra"-e Director

ln

Otragadougou was enlarged.

by tlre transfer of staff

^from

^the

^support

unlt ln

Genena, and

a llalson office

wae estabLlshed 1n BrazzaviLle.

lllre Kingtlom

of Belglun,

Canadar

tire

^Republlc

of

^trhance,

^the

^{FederaL Bepublic}

of

Germany, Japan,

Kuwait, the

^rirrgdom

of the

Netherlands,

the

^llnl.ted Klngdon

of

Great

Brltaia

and

l[orthern Ireland

and

the

United States

of

^Anerica.

lhese

contributgrs

were

Later joined

by Norrray.

1

Chapter

I

page ₇

20. lhe

tæansltlon was

smooth.

ktr»erience so

far

lnd,lcates

that

the

centrallzatlon of actlvities in

tJre

flelê

^{h,as hatl,}

the effect of creatlng

^a

closer

associatlon

wlth the cl,lfferent

leveLs

of akuctnre lncluding rrlth

the

participating corrntries,

and.

a greater flexibillty for ^the

nanâger:ent.

2J-. ^îhe

lnter-a€ency Steering

Comlttee for

Onchocerciasis

Control

1n the

Volta Riner

basln

area,

which bad been

particularly aetlve

durrn€

the

preparatory and lar.mching ^phases

of the

Erogranrm€, has proved

to

^be

^{a valuable} tool for

coneerted

action

and

rapld

decislon-naklng.

NationaL Onchocerclasls ^Co@Ltttees

22.

^By

nlit-1974;

each

of üre Participating

eorrntries had

fornally

establisheô

a lfatlonal

Onchocerciasls Conrnrittee

(iiOC).

[hese

Comittees

played

a najor role ln

resoLving

logistical

^problens

during the fj:rst

years

of

operatlons.

2r. ^[he flrst jolnt

^meetlng

of the

^I[OCts which was convened

ln

^AUid;an

in

June 1977 wae

extrenely construetive. It

was unaninously agreed.

that

^such

meetihgs should become

a regrrlar feature

and

at the lnvltatlon of ^the

^Government

of

^Ben'ln

a

second meet{ht

took

place 1n Cotonou

in

June 1978.

Advlsor.ri

bodl""

24. Dring the flrst ^forrr

^years

of activlties the

^P3og3ame bas

benefittetl

^ron the

^{guid.ance and sunport}

of tire

ad,visory bodles.

25. In the lnitiaL

stages,

visits

were roade by nerabers

of the

^Eeological Panel

(nf)

_ana

Scientlfic

and

[echnical

A(lvisory

Comlttee

^(Sni.C)

to

the

Prograrnrae area

for

dtscussions w:lth

tle fieltl staff,

^and

to obtain first

^irand.

haowledge

of ^the

enrironrnent and

of the operations. Iÿith the

^etçpiry

of

the

Chaoter

I

page

I

nantlate

of

^members

of

^SîAC

at the

end

of

J.97q

the

eonpositlon

of the

^Commr11g.

was reviewefl antl

sllghtly

^roodified

to neet the

changing

neede.

Fol1ou1ng the

hansfer of

management,

a joint

meetlng

of

both ^groups

took

^place

ln

Oragadougou

ln

L977r

followed

bJ,

a

meeting

of

^SîAC

at

f,hs ^TfrIO Regtonal

Office; Brazzaville,

in

^1978.

26. lhe

Ecologlcal Pane1 has been

revlewing the

data

collected by

the hydrobLology research workers rrniler

the aquatlc nonltorlng

progr4rme and be's

drawn

attentlon to factors

which miglrt be

detrimental to ^the

environment.

27. Of

equal vaLue has been

the role of

^STAC

in evaluatlr:g tire tecirnlcal

aspects

of the

Progra"tme and,

notablyl giving

guidance

in

research.

28.

^Altbough

_efforts

were rnad.e

to otninize d,uplication

thror:gir

jolnt

neetlngs

and. tiirough cross-representotion

at

rneetings, sone overlap between

the roles

of the Sclentlflc

and Technlcal Advisory Comnittee and

the Ecological

^panel has

not

been completely avoid.ed, and

solutions to tiris

contlnue

to

^be

sor.rght.

^One

possLbility

mlght be

to

^malce

joint

raeeti-ngs

a

pemnnent

feature or to

merge EP

lnto

^STAC.

29.

As Àd.m.lnistrator

of the

Orchoeerciasle Fnnd

the

^{Ïÿorld Bank}

is

responsible

for nobillalry

^and, uanaging tJre fr:nds

required to

camy

out the

hogranme.

Advances from

the

^tr\rnd,

to

^'i?HO

are

nade on

a quarterly basls

on

recetpt of

^a

rrltten

submisslon

of the

estlmated. pa;rrnents

to

be uaile dr.uing

tire following

quarter. At iialf-yearly i.nterwals,

ti:.e ^tsanl< provldeo

to

each

of the contrlbuting partles

and

to the

^Steerlng Comrnfttee,

a

statement

of contrlbutlons, recelpts of

and disbursements from

the

^tr\rnal.

30.

^Ae

of

Decenber 3]-,, ^L9T7?

the

anount

of

advances

by the

t'Ior1d Bank was

§3OI2OO?O00

of

whlch *zOr2oOeOOO

for the

19?4-1976

perlod

and $IOTOOOrOOO

for

^t9??.

ît

oo)

r

o,

@o,

c

)

I

!

z

o o3

! I

\

no

{,

ag'fr

h\§c ^(.) 2.\-

)

\\ It

ls

2

m m

EU, U,D

o

! j ô s

z

m m

2

!:E

D

'Tl

(D (D

o€ f

ào o

-

3

!=D C

-

D

z

D

-)

J

I I I

i

I I

! I 1r,m

z

m

ô ô 3

@

t

oo :,Ol

r

C)§

lÈ

=

of o

À,

q,

Ol

3o,

r

o

-

D

tr

*t

!

o

6)

*t .-.-

= =

m

Dm U'

o

'Tt

z,C

*t

(t) æ o

À

ô

\

_a

z

! I

i

I

! I

o

(D.3

-{D E

=

C)

o ô

mD

=

2

6)m

-

a-o)

(ao

6)

=

m

=

D

I o

\

6 I

(DF m! D

x

o J

o-s

o,

)

6)

-

D

=

D

ôC) o,

§

&

.-?

\.

c

_!

t

!

o

F

{

D

zol

./ \'-.2'- -'-'a.

r'\.-.-.-'-.-.

Em

= =

'-'4.r'J''J'\'''s.

o

6)

o

\

\\

I

II

MANAGEMENT STRUCTURES

r

Specral Fund for 0nchocercr asr s

( IBRD )

Ecologr cal Panel

Scientif ic Advisory

Panel I

Economr c Development Advrsory Panel

I

I

I I

I

L

J L

-J

r

Scientific

and Techn Advisory Committee

ical

|-

-l

I Onchocercr ^Natronalasr s Commrttees

wHo 76409

-t

J

I

L

JOINT COORDINATING COMMITTEE

SÏEERII{G COMMITTEE

E)(ECUTING AGENCY

(wHo)

External Relatrons and lnformatton

Programme Director

0nchocercrasr s Eprdemrology &

Publrc _Health

Adminrstratrve Support Servr ces

Sr mul r um Control Operatr ons

Economr c Development

Unt t I

I

I

CHÀPîER

II

rre

^{PROBTEM 03} O.TCHOCERCIASIS A1TD $TE OBIECTIITES OF fiTD ^OCP

Â.

CEICHOCb:RCIASIS

lhe

dlsease

the

^paraelte

1.

Onchocercla.sts

ls

a

parasttlc

dlsease canrcett by a neroatode

of

the

fllaria

grourpr Onchocerca

vohnrlus.

Ehe pars.slte

ls ^str{.ct1y

assoclated

wlth

nan and has no krown anlna-I

resernolr. It ls transuttted,

by

several illpteran flLes of the srnrullidae fanitÿr

whtch

lneludes the tlest

Afr{.can

vectorsl

the speeles conplex

@. ^[he

Si-utr].tun

or blac]dly ls

^both

vector

and.

lntemedlate host :

^a

mierofilaria

lngestetl

fron a

^{ÿtunan her,s}

to corplete

a

deveJ.opment

cycle rrlthln the blactcffy;

1n about seven days

lt

becmes an

infectlve Iarvs, the only

fo:m whtch can

infect man. there ls

no

posslbility of

propagation

of the

ùisease except by fo:mrs

of the paraslte that

have completecl

tlÉs obligatory intraveetorial

eJ'cle.

2.

Aalult Onehocerca voLrnrlus vrorrIrs rnals and

fsrnals, l1ve ln

^tuxnan tissues

either in the free state or

encapsrrlated

ln

fLbrotrs formatlons lorown as

onchocercorus,

eysts or nod,trles.

Ehe

free

wortff and deep-seated nodules are

nornally undetectable. îhe superflclal

nodtrles; which are

rrlsible

and. pa1pabLel

are

mostly

located in the

subcutaneous tLssues

overl;rlng

bone:

eostal

marg:in, iLLae

crestsr trochanters,

sacr:Lrm, loaees,

shlns, slorll.

Each

cyst contalns

one

or

more

patrs of tzo:us.

As

a rrrle patlents

have

several cysts or

^groups

of cysts,

an6

in

nodulectmy carFal6ns

there

have been ca.ses where over 40

eysts

bave been renoved

fron a single

pati.ent.

3. ^Drring lts lifetfuae (estinated at

LO-15

years) the

female Orchocerca

produeesmj-Lllons

of

enbryos,

nierofilarlae,

rzhich spread ttrroughort

tbe

bo4y tissrres

but rvith _a particular aJfinit;' for ^the

sicln end

eyes.

Fron

the skln

they nay be

lngested by

a Dlacldly during lts

^blooct

meal. In

man

the nicrofilarlae

have a

life

expectancy

of L-2 years. After thls time,

unLess they have been ingested

by

a blackfly

and

are thus able to

^coatlnue

thelr

deveJ-opmemt c;rc1s, they

dle tn

the tisstres.

Chaoter Page 2

4' îhe naln clinleal

naÂifestati-ons

of the

disease

are

due

to reactions to the

^presence

of nLcrofila.r:lae'

_ancl

t4eir severity is directly

rela.ted,

to

the

lntenslty of ^paraslte infectlon. 15" srnplest nanlfestations _are skln

1esj-ons vrhlch

are

caused by scratchj-ng, _and

are

folLowetl by

pnrritlc papular

enrp11onsl

rater

on

the

slÉ-n m4r r-uadergo a var{.ety

of

changes:

thlclrening

ancl sclerosLs

tn the forn of pac§dema

(erephant _skia)

I

^localLzed

^or

^extenslve cutaneous atrop6y, and depignentatlor.

DLs

tri

butl on

of

onctlogercla.sis

5'

Onchoeerclasis

ts essenttally a

^disease

of tropical _Afr{.ca,

where

1t ls

prevalent to varying extents

betrveen

latihrdes IIoN

anct

15os.

Eowever,

lt

also

affeets

tvro

other continents:

aroer^i.ca, r,rith

focl in

Guatenarar L,Iex[cor venezrelal

northem Brazill

and' coloanbla; _and

Asla, vrlth the

foeus

in northem

^yenen.

6'

^Broadly spealclnÊ,

the

northern lirni

t of the

disease

in Africa

nrns

fron

Ganbia

to the

soutl:

of Iah

Chad;

lt

then rj.ses

in the

Sudan along

the Nile

as

far

as

the

Abu Haned reSion

(rgofltN)

_{and drops agaln}

into Ethiopla

_{along the}

tr''hrtaries of

the

Nile. îhe cor:ntries

sLhrated _between

this line

antl

the

Equator

are the

urorst

affected: _the

_rvhole

of lïest Afriea

^(except

tfanrLtarria),

carneroon, southern

chad, the centnal Âfrican

Ernpire, southern sudanl rvester:r

Ethtopial

and

northern

_Zal::e.

7' Purtber south, the

dlsease ocsurs 1n

Equatorial

Gulneal Gabon, Congo, Rvranda, Brrnrndlr

the

eecxtrar basin antl southern

part of zairel

uganttal western I(enyar Tanzanta, AnSoIa, ancl

ldalarrl,

where

it

reaches

lts

eouthenrmost

pointr _l?os.

Chapter

II

Peae 3

îhe vector

and transrJssion

ÿector

speeies

8.

llhe l.raorwr

vectors of

^ht'man onchocerelasis

are fllles

which belong

to

^the

Si4ü.11tlaefertl1yo[heAfrc.canvectorsaremerrbersofthecomp1exeS@

dannosum

(tfrroughort tbe

area

of distrihrtion of the

cllsease) and

@eavgL (in certql" ^parts of

centrral and, east

Africa).

As rega:stls

S.

d,agrostm

s.1., lts

area

of dlstrihrtion

extends northrvarrls and souttnvards beyontl

tbat of

onchocerclasis.

fhe S.

dar:nosum complex

9. It

has been

lmorr for

some years

that S.

damrosrm,. _once reganled as a homogeneans

speciesl tn faet constitutes a

conplex

of d.lfferent taxa.

^As

a result of studles

pursued 24 separate cytoJ.oAca1 segregates b.a.ve been

ld-entified,

throughort

lroplcal Africa. 8or ÏIest

Affi-ca

nlne

segregates have been describetl.r

slx of

which

(rrllll"rrr trsirbattt

ttBandamatr, rrsotrbrert, rrYahrr,

ttBillerr) _are of direct

^concern

to

the Prog3arme because the;r

are

found

in or closely

assoclateê wj.th

the

pr"ogrernme area,

At a Scientific

Aduisozy PaneL meeting on

veetor

complexes

the

d.ecision vras endorsed,

to consiiler

these as specles

with the follotring

nanes

alreaily

glven then

in

publlcatimsr llgggg

^soso, S.slrbanumr

S.salctlpaulir

S.soubrensel S.yahense and

So soüanosün respective3.yo

10.

îab1e

I

æd

FL6.

shotr

the dlstribution of

these

six nsln

species

for

the whole

of ïfest Africa

and

for the

Programe ar€a and adJacesrt zones

respectively.

11.

Each

of the

specles has

a eharacterLsttc dlstribution pattern

_reLated.

to the d.lstrlblrtj-on of ^the bioclinnatlc

zones

of

^lTest

Africa. [hrs

Ë.sanctlpau].i has

never been demonstrated

ortsltte the forest

zones; SoseuanosLm and S.yalrense

are

more

ublqultotts but nainly

ccmfined

to certain t;pes of

natereourse

in vell

nooded

couoetry; Srsoubrense ^rns-iu].ÿ

lnhablts the

lerrge r{.vers

ln ^the forest

and Gui-nea

[able

1. DISîRIHJEICN- OF SP-:,CIIIS OF S.DAI'NOSIM COHPITEX

§PECIDS

Bquamo§utr

-

Chapter

II

Page ₄

TIÀBITAT

hrllid forest

and

riverine forest in

^Gui.nea saÿanJra

llrrLld

forest

and mourtain

forest;

erüectd.s

into

savanna

in

^Guinea

lxrntd

forest

and. rtveni-ne

forest,

extend.s

lnto

savanna

ln

^Guinea

hurttd

forest

hüttd forest

and Guinea saÿannai extemdE

into

Sutlan savtrlna

Sutlan savanna.; extends

into

Grdnea saÿanna and even

forest

.ÿahense

Eoubrense

sanctloauli

-

daxnnosum

s.g.

slrbanum

ITTDICATIOÏ OF DISîRIH,IIO}I

Canerom,

Beninl [ogol

Ghana,

Ivory

Coastl Upper

ÿolta îogo,

Ghana,

Ivory

_Coast,

I5.berial

Guinea

Benlnr

îogo,

Ghana,

Ivory

Coa.st,

Ltberia,

Guineal Upper Vo1ta

Ghana,

Ivory

Coastl

Ltberia

Cameroon,

Ifigerial

3entn, llogo; Ghanal

Ivory

Coast,

Iiber{.a1

Gulnea, tr[a].l,

Nlgerl

Upper Yo1ta

Cameroon, NlgerC.a, Benlnr _llogo, Ghana,

Ivory

Coastl Guinea, Ga.nbiae Upper

Voltal

lrÎallr Nlger

tr, U' 7)

@

c

oz,

o1t

a/,! m

I

man

o'lt

t?

loID t<

lz.lo

lqtlc l=

c)o

=

! mx

o o_c

@

=

^ o

a\)

tr

o

D

»

E_ê F

2ËfrËâE

.\Jc

o() D

t

o

§_c

t-o

=

m

N)

()o

-{o oz c

t- oo

ltt

:.' È

cr N

§\.\o\

oC

>.-_..

6,

oo CO6)

oC

tr »

»

D

J _.t

-{

,

mz

^o 0o

6ro

@o

@o

I

I

oC

|-

UIah

o

D

o

l-rn

o

a

»

a

»

x z

I

9m

@o

Ca oC

q,o t-6) -{

zô

a

§T

a§-'

@

z'Tt

ot

.l

J

o

z

I{

z o6) C

§

€

tr

D

0ut

1\

xo

,

T oo oa

-{a

3

m

mz o

e/

{

t

!

xo c

a o^

oS

tr

4

Ohpora

EDê È

q

ê

§

o_ê

lê Otr

ouow

o

*

o@

C

xm a

{

x

1.

!

Èa

tr

o

^a C

I

=

>o

§

go

L

*

nqso

z

=

m D

\

Chao

rII

Page 5

savarurs' zonesi §.d'amnosun s.Eg

ls

for.rnd

nalnly in the

Grrlnea savanna zones;

S.

st

rbanr:m has been

fourtl in forest

areas

hrt it is

^meinly

ln the

Sudan savanna zone and

the

Northern _{Guinea savanna}

that this

species

ts

w!.despread.

L2' Dlfferences ln

transd-ssion

potentiaL

_{have been} rlenonstrated _between specles

and. as

a

fr.urction

of the bioe]lnatlc

zones.

Bio-ec olosÿ

of the

ve

ctor

L3' trike all

brackflLiesl §.d,amostr.n

s.1.

deverops, duxing

its larral

and pupal

st€esl ln

nrnning

rvater-

Pre-ad,ult deveropment (eggs,

rarvae

and pupae)

trsts

about

a fortnight

uncler

troplcal

nrnningdyater teraperattEe

cotditicnrs.

The

various

_specles

of the

complex have sonevrhat

different

requlrements

urith

respect

to the

p[yslcoched-cal

conditions of

the

water of their

breedlng sLteso

14'

Among

all the biol-ogical peeuliaritles,

_trzo fun6anental eharacterâ.stics stand

out

because

thel'

deter-nine

the strategy

_and

tactics to

be eraproyed against S.da.urostm,

(i) _lhe

_demands

_{of the rarvae of the}

_comprex

are relatlvely

exactlng,

partlcularlly ln

regard

to their nutrition. [hi.s ls ^reflected in Ii'nrted spatlal dlstributlon of the

breeding places _and

is

what makes

lt ^possible, _{after a careful}

_surxrey

of

those breeding

praces, to

lnplenent a

eaq>atgn arued

at destroying, wlthln a

glven _{area and by}

sn'rfflcient§ spectfic actionr +1l the larval

popurations

of the

specles.

Chaoter

II

Page 6

(ff) thts factor,

favourabLe

to the

execution

of ^a

coordlnated ca4ral€1rr

is unfortunately

cor.mteiUatanced by

the ftyine

^power

of the

femalee;

whencel on

the

one banrd,

the

neetl

to

^contlnue

larvlclding

^{over a}

very long

peri-od

to obtain only a satlsfaetorlr reduction ln

^the

paraslte

populatlon harboured by man; and, on

the other

hantl, the need,

to a

_DIy treatment

to a snffieiently

extenslve

protectlve

_zone

Eo a,s f,o mln{mfze

the

consequencee

of ^posslble

reinvasions.

Transmlssion

15.

^llhe

ulcroflLartae of $.-Wlg4ggl ^the

patirogenic agent

of

hrnan onchocer-

claslsr

have

to

^go tbrough

a

stage

ln

a

vector in orrler to

^conti.nue

thelr

development. îhese

d.cnofllariae,

tngested drrrin5

a

blootl

meall

r:ndergo severaL moults

ln the

course

of a cycle that lasts

an average

of

seven

d.ays.

^On

conpletion of thts cycle, the infectlve la":rae

break

out of the fly ^during

^a

subsequent blootl

mer]. In ^rlew of the duration of the

gonotropbic eyele

of

the femal e

S.

dannosmr

Lt is

rmFossible

for the parasite to

^go through

a

coupLete

cycle

between two srccesslve blooil meaLs and an

infectetl

feuaLe w:tL1

not

become

epldeniologieally

clangerous

r:ntiI

she talces

a thirrt

^blood meal.

16.

^{llhe dlmapics}

of

transnLssion tlepend on nany

factors, the

main ones being:

the

absolute

quantity of

^potentlaL

vector

bllaclcflles;

the

mean age

of the vector

populationsi

the veetor

specles coneersred. (adaptation

to the parasitel

degree

of

anthzropoplû}Iy,

etc.)

_;

the transrission

^season;

Chaoter

II

Page ?

the

degree

of contact

between tnuuan and

vector populatlons,

_ç,hlch

depends on h,man

aetiv:itlel (tintea to

age and

sex)

and on

the

above- menttoned

factors;

the Level of infection of f,[s

^]nrrnan popurationa, _nh.ich

are the

only

regenrolr of the

pathogen.

Epidenlologtr

of

onchoeerciasls

17' ^I[ot a]l _the

tleter:ninin.g

faetors

_Ln

the

spontaneous develooment

of

onchocerclasis _have

yet

been foturd,

hrt a

number

of

general

nrles

can be deduced

from obse:rrations so

far.

te

bulld-uo

18'

orchocerciasls

i-s a parasltic infection that

pro,gresses slor.ày as

part of a

cumulatlve

process. îhere ls a long period of cllnl.car _ratency after infeetion

(one

year

on

a"era6e).

§pontaneous cure

is

belated antt

is

_S0verned by

the life-

span

of the _adurt

vorm (1o-L5

years).

Und.er

stable conditions of

transrulssion,

the fllariar load ln ttre indlvidual steadlly

increases

orer the ÿêêrso

^The

severity of the

Lesions

varies

cllrectLy

with the

{egree

of paraslte infectionl 1oê'r rrith the

nunber

of adtrlt

r/ol"ttrs

in the

body

of the host

and

the

number

of mierofllariae _they release.

trevel

of transnlsston

_{and. J.ength}

of

exposure

to braclcly bltes _{are the}

_üzo

_factors in

nân-vector eontact

that

^govern

parasite hrild-up.

L9' rn fotE _viLlages of the

Programe

area, it

rras posslb].e

to

d.etermtne annual trangntssion

potentials (em)l,

_before

_the start of the

comPatgrr over a

sufficlentLy

_rong

periotl to

have

a

^good

ldea of the effect of

annua-l var{.atton.

Medical examination _{ha.s sho'ne}

that

c.cposure

to increasing

Arp Leads

to increasingly

severe onchocerciasi-s r.eslons _anong

a

popu-lation.

1

For

an expranation

of Aîps

and. ÂrJRs see

footnote

_on pages

r.o-rr,

cha!,ter

rrr.

Chaoter

II Pagé-8-

20. [his

crlJtrrrlatlve

effeet also

sirorzs

ltself in the

connerion between inereasing leveLs

of

preva-1enee and

increasin6 paraslte load. îhe greater the

proportion

of affected

persons

ln

a

rillage, the greater thelr

para"site 1oad, and rri.ce versa.

Geograptr.l ca1 illspar{.fi. es

2L.

Onchocerclasis occurs

in foei,

each

of

whlch

is

ceatred on

a

breectlng p1acel

or

succession

of

breeding

places, ln the

lnmedlate

vlctnrf,y of

lvi:ich

the

dlsease appears

in lts nost

severe

fotrt. îhe d.istrtbution of foet is

^governed by the

§drogeographical features of the reglon.

Depending on

the denslty of

bree6ing

places, foel

nay be

relatively _extersive

_and, contlnuotrs,

or

separa.te and

restr:-eted in

area i.:r a nosaic

patternl

22.

Eaderoieit;'

in

any 5'iven focus

falls

o1!1f

rrith

increa.sing distance from the

centre. This stra,tiflcatlon into

leve1s

of endeulclty (tirst-L1ne,

second-Lj.ne end

third-Ilne viLlages) is

go'.'erned. by

the

frequeney

of contact

between nan and

veetor, vl:ich

decreases rvi.th distance

fron the 1anral

breed,ing pJ.ace and the dlstance over *rirtch

tire

blaclcfLy ha.s

to travel.

Role

of

sex

23' In

zones

of

^lorz

or

moci-erate end.e'.ni

cit;r

psp are

nearly

always

affected

more

frequentry

than tvotllêrlo

îhls dlfference

_leveLs

out ln

sperenir-erclc zones, rhere

the

prevalence

of

onchocerciersls

is the

sene

for

both sexes, _althorrgh

rolcrofiLarial

1oa.ds

are sti1l generally higher for

men than

for

rvonu,,.

24'

îhese

dlfferences are

aLso euident

in the

fi.gures

for the

prevalence

of

eye

lesions

_anil

bllndness,

rvhich

are

a-lvrays ht$aer

for

^men.

Che.oter

II

Page ₉

25. lhe

roost

valitl

explanation would seen

to

^be

a

soclologiea.L

one.

^Because

of the dlstrihrtion of

ta.sks and

the social tltrision of

Labour, tvom,en are

less

exposed

to cortqct vrith the vector. §rmilsr'ly, ln

two

villages ln the north of the Ivory

Coast

tn

^{whlch women}

are signiflcantly

more

affeeted

^t?ran nen,

it

^has

been shovn

that they

alone

are

concernetl

in the cultlvation of rice

along the r{-ver benks

nhile the

men grovr

cereal

crops

further

away

fron the

breeding

sites.

26. Thisl

horvever, does

not

exelude

the possibility that

o';her

factorsl

such

as horaonal ones, nay be involved.

2'1.

^Studles conducted.

in the

^OC? zone

in just

over ₃₀₀

vilLages

hane shorvn

that there are

trvo

distlnct

tytrles

of

entleqic

situatlon

one

at

each extrerne:

(i) _{a level of}

disease

that

^roay be eonsidered

"tolerablerrl in

vtÉch the prevalence

of

onehocerclasls

in the cmunlttes

considered does not

exceed

lÇl; ^posltLve

cases have

less

than 1O

nicroflLar{.ae

on

average

per skln blopsy; there ls llttle or

no severe eye tnvolvement;

the

frequeercy

of

bllndness

is

^belovr

lfi *ra r.esults

frcno diseases

other

than onehocerciasls;

(rf) a leveL of infection at

^rvÏr-leh

the

tllsease

ls

^octremely severe; aIL

v:lJ.J.ages

ln

rzirleh over 5/o

of the regtstered population ls blind

have beesr found

to

^{have more} tban 6@

of their

lnhabd.tants

lnfected;

posltlves

_have

orer

20-25 rd.crofiLar{.ae

per blopsy;

over 1@

of

octrlar

onchocereia.slE

leslons are

severe

anÿor lrreversible.

Chapter

II

Page 1O

28.

Althoueh

there are

v:L11a6es

in

which

the

prevalence

of

onehocerclasls

ls

wer 6$ while the

frequency

of

blLnduess 1s

less

tttæt

5/q

^{tb^at}

}gÿel urst

^be

consldened as

a

threshoLd beyontl rvbich

a co@rnlty is at ^high risk. It

would

therefore

seen

Io5:ical to redefine the fotr

conventional leveLs

of

^endemr

clty

as

follovs:

(i) (ii)

Sporadlc cnrchoc

erciasls : fewer

tinan Lÿfr

infected, natnly

etront

adults.

H:moenderd.clty

I

betlveen 10 and 29.ÿ/o

lnfected.

îhese genera1ly _have

less

tban

Io uicrofilarï.a per

blopsy and eye ccnapllcations

âr€

râipêo

I'fesoendenlclty

:

^betrrreen 30 antt

59.# infected. îhls is

an lnte:medla,te

sitLlatlox in

rrhich

the

population _{may show}

varying

clegrees

of ^paraslte lnfectlon

and j-n wtrich

the rlsk of

eye comp]Lcations i.ncreases

with ulcrofilari.al

loed.

Hÿlerenderieitv 3

^{over 6@}

infected,.

There

ls a high rislc of

eye

conplicatiors

_and

posltlves

_{have more than 20}

ntcrofilar{.ae per

blopsry On glrera€e.

(ur)

(r")

Chapter

II

Page

IL

3.

OBIECîMS 03

îre

^oCP

29. In

nany

African

cotm.trLes,

parasltlc

diseases

are

enderulc. Ho.rorerl

during the

196Os, seven Flest

Afrtcar

go\rernments decltled.

to ^put

^{enphasls on}

the fight agalnst

onchoeerei.asi.s.

In fact, nost _troptcaL

diseases can be

6ealt with efflciently only vithin the

frarnewor.k

of a global pollc;. of

heatth

lmpzovement, wi:ich

involves a slov

^process

of instlttrtional

and beharrloural

change.

Oa

the other

handl oneirocer.ciasLs, whlch

is also

hrovrn

to

have serc-oua

social

and econouic repereussions,

apart fron

being a

particurarly

sad

h]ItralIitarian problernr can be taclcled by

vector control

cecrFat6ns,

uslng speclfle

mocl.err teclmolory.

30. ^îhe

^Vo1ta

^Rlver

^Basi.:r area \za.s hrouae

to

be one

of the

rzorst

focl of

oncho- cercla.sls

in the lvoi.ldo [hl.s

has been

further

eonffuued. by

t]re

epideraiolog.ical sur\r'eys

ea:ried out

by OCp

since L975. îhere are

sever"al lgperendenr5-c areasl where more ttran æfr

of the population

bave onchocercLa.sis, which

v:trtuatly inpLies tlut

eve4'body

fron the

_age

of

10-15 years

is infected.

I{o,*e than LZfi

of ^the total

populati-on uay be

brind in

such

viIIages.

3L.

^Ellndness

constiürtes the best

homa _and most

inportant

roedical consequence

of onehocerclasls. Also the

concentratlon

of

bllndness

in

smalL nrru-I

comunltlea, rvith extrenely htgh

bltndnesE

rates in relattvely

young age-groups (see

Flg.

₎

severeLy

affeets the

working

capacity of

^an i-uportant parü

of the

popqlatton.

Ia

§perentlerÉ.c

areas,

onchocerciasls cornpletely d.oroinates as

a

capse

of

20

AGE DISTRIBUTION OF BLIND MEN IN I5 HYPERENDEMIC VILLAGES

Blindness due to onchocerciasis Blindness due to other diseases

10 20 30 10 50 60

^?o

r5

co (, o-o

r0

5

No

€N

o

, \

/ \

/ \

/ \

/----/ \

\ \

.a --22

a

Age

Chapter

II

EEBeE-

blindness. Iligher

bllndness

rates are

found

ln

^rc.ver basins where onehocer.clasis

is

^hrown

to

be preva-lent and severè.

,2. ^{Apart froa} total bllndness,

sevene

visual

^handi.cap due

to the

tllsease nay

constihrte a tlisabiJ.ity

eqtrlvalent

to bllndness. Also, there ts

^{nov some}

eridence

that the life

expectancy

for the blind in Africa

nagr be shortened.

33.

^Another

social

consequence

of

orchocerciasis

ts

ilenographic inconsistency wiÉch

affeets the very stmcture of the

populations _oqrosed

to the

d.i.sease.

îhe

departure

of

^yol.lng nen ^(beüneen

the

ages

of

15 and

30) tron

an

infected

village ls part of

a

n.ch

more rid.eqpread tendency

to

^emJ

^grate

torzards

the

torars

of coastal regions that

bave bet'i;er resources than

the

s&ÿ?nnâo llhen

thls

happens

the

d,emographtc imba-lance can be seen

fron the

age pyramlds, _whj.cb

to varylng extents d.iffer in

^shape

fron the nomal,

rerrealJng a

nald.j.strihrtion of population

by a€e and

sexo In the

tSrperandemtc zone

of

norühem Ghana,

for

examloLe,

before

the Progra:uae

started _there

_{were 65 men}

for

every LOO women

in the

15-44

year

age group;

ln

sme vLI.lages

the proportion

vras even as

low

^as 60

or

551 whereas

the natlonal

average was 9J men

per l0o

^vromen.

34. criterta for the selectlor of the

area

for the

canpatgn lncructect the acti.ve

lnterest of the various

govenrments concerned,

avatlabiLity of

^d,ata

concern-ing

the naürre

and sever:Lty

of the ttiseasel the

presenee

6f

rn*rrortant areas

of

^severe

ffirerend.euiclty

^trrith

hlgh rates of

bLindnessl

the

e:clstence

of a

borl,o

of information

concerrring

tire cTistrihrtion

and beharriour

of the vector, the avalIabillt;r of

adequate roaps ancl

§rdrolog'ical lnfonaation. It

was consirlered,.

that

any

vector

controL somsalgn would have

to

be on a

large

scale

if

^success

wae

to

be achleved as

lt

nas already heovn

that S.

dannosum va.s capable

of