ANNUAL 7-l I ocP/EAct4.2 IN

WORLD

HEALTH ORGANIZATION

ORCANISATION

MONDIALE

DE

LA

SANTE

ONCHOCERCIASIS CONTROL PROGRAMME

IN

WEST AFRICA

PROGRAMME DE

LUTTE

CONTRE L'ONCHOCERCOSE

EN AFRIQUE

DE L'OUEST

EXPERT ADVISORY COMMITTEE Fourteenth session

Ouaeadoueou.

7-l I

June 1993

ocP/EAct4.2

ORIGINAL:

FRENCH

ANNUAL INTERNAL TECHNICAL

REVIEW MEETING (Ouagadougou, 22-26 March 1993)

ANNUAL INTERNAL TECHNTCAL REVIEW MEETING Ouagadougou, 22-26 March 1993

Table

of

contents INTRODUCTION

IVERMECTIN DISTRIBUTION

Strategy, modes

of

distribution and actors Results

Impact

of

ivermectin on onchocerciasis transmission

Impact

of

ivermectin on the evolution

of

ocular lesions and other forms

of morbidity

. . . ^.

2.5. Research on effects

of

long-term use

of

ivermectin

l.

2.

2.1.

2.2.

2.3.

2.4.

ocP/EAcr4.2

ORIGINAL:

FRENCH

...9 ..

^t0

l0 ll .t2

2 2 2 4 5 7 7 8 E

3.

3.1 3.2 3.3.

3.4.

3.5.

3.6.

EPIDEMIOLOGICAL EVALUATION

New epidemiological evaluation strategy and prospects . . . ^. Consequences

of

large-scale ivermectin distribution on the epidemiological evaluation

of

vector control

Immunodiagnosis: Development

of

a serological test Ophthalmological evaluation

Definitive

cessation

of

larviciding

in

the original Programme Human migration studies

RESULTS OF VECTOR CONTROL AND VCU RESEARCH Entornological evaluation

(March

1992 to February 1993) . . ^. Summary

of

post-control studies

Larviciding and aerial operations

Results

of

^parasite identifications by

DNA probes

. . ^. Results

of

vector

identifications

. ^.

Resuls

of

experimental studies on transmission Aquatic monitoring

6.

EPIDEMIOLOGICAL MODELLING

area

DEVOLUTION

Institutional framework and roles

of

the principal actors

Proposed entomological surveillance

in

the context

of

devolution Support

of

OCP and IVHO/AFRO to devolution activities

in

the Participating Countries

4.4.

Mali's consciousness-raising committee 4.

4.1.

4.2.

4.3.

5.

5. r.

5.2.

5.3.

5.4.

5.5.

5.6.

5.7.

OTHER MATTERS

Research, Coordination and Collaboration Computer assistance

Publications

8.

CONCLUSIONS AND RECOMMENDATIONS 9.

LIST

OF PARTICIPANTS .

IO.

PUBLICATIONS

t2

..12

t2

r3

.14

...14

7.

7

.t.

7.2.

7.3.

l4

2t

22 24 25

2t 2t 22 22

.14 .16 .17 .19 .19 .20

I1.

^FIGURES, MAPS AND ANNEXES 26

ocP/EAcr4.2

Page 2

I

INTRODUCTION

The Annual Internal Technical Review Meeting was held

frcm22

to 26 March 1993 at the headquarters

of

the Onchocerciasis Control Programme in Ouagadougou.

[t

^was chaired by the Chief

of

the Vector Control Unit.

During the opening session, the Programme Director, Dr Ebrahim M. Samba, welcomed the participants and mentioned the ^presence

of

the National Coordinators who were taking part

in

the meeting

for

the

first time.

He emphasized that the results obtained

by

the Programme were ^good because

of

the

efforts

made by OCP and the nationals.

The

Programme Director

drew

the attention

of

the participants

to

the

fact that it

^was

important for OCP to continue to make savings as in the past. Because

of

the world economic crisis, the donor countries were having

difficulties

in continuing to finance the Programme. It was therefore necessary to make savings on

all

the budget headings and continue to work

efficiently.

During the meeting, the technical subjects concerning ivermectin

distribution, epidemiological evaluation, devolution, the Vector Control Unit and applied research were examined.

After

the adoption

of

the agenda, the recommendations made during the previous meeting were

reviewed.

On the whole, they had been

or

were being implemented. The recommendation concerning the identification

of

an epidemiologist

in

the national teams was renewed.

2 IVERMECTIN DISTRIBUTION

2.1.

Strategy, modes

of

distribution and actors

The strategy and modes

of

ivermectin distribution

in

the OCP area could be summarized as follows:

-

Large-scaletreatment

-

^Mobile treatment

-

^Passive treatment

-

^Community treatment

-

^{Other modes}

of

treatment.

2.1.1.

Large-scaletreatment

This

type

of

treatment depended on the level

of

endemicity and the risk

of

onchocercal blindness. The objective was to administer the drug to as many people as possible who needed it.

Priority

was being given to ^areas with CMFLs (community

microfilarial

loads)

of l0

mf or more per skin

snip.

The areas concerned were

in

most cases the western and southern extension zones where vector control was going

on.

However, to the north

of

the western extension zone where ivermectin was the

only

means

of

control, the large-scale

distribution

was carried

out in

zones

with

a CMFL equal to

or

less than 5

mf/sl.

Large-scale ivermectin

distribution

was also carried

out in

zones

which

had particular problems,

viz.,

the Pendie area

in

Burkina Faso, where a residual transmission was noted

after

the cessation

of

larviciding, and reinvasion zones like the river basins

of

the Black Volta, in the Bui area, and

of

the Kulpawn-Sissili where the vector control had encountered

difficulties. This

mode

of

distribution was also undertaken

in

the intermediate zones in southern Cote d'Ivoire.

Large-scale ivermectin distribution was carried out by:

(a)

national onchocerciasis control teams supported financially and logistically by OCP;

I

mf/s: microfilariae per skin snip

ocP/EAcl4.2

Page 3

(b)

local teams which received help

from

non-governmental organizations (NGOs).

National ivermectin distribution teams normally comprised a permanent

staff

made up

of

nurses and technicians supervised by a medical

officer

who was the National Coordinator. To that team could be added nurses

in

health ^posts

in

the zones under treatment.

Large-scale treatment required many days in the field, workers and vehicles and could cover a whole

river

basin.

With regard to local teams, mention could be made

of

that

of

the Lunsar Eye Hospital in Sierra Leone, financed by an NGO, Christoffel Blinden Mission (CBM), _and which was involved in the large-scale

distribution.

The team wzxr composed of four ^persons who were ophthalmic nurses and health workers; there was no medical

officer

in the team. Just as

for

the national team _{, the} objective was to make ivermectin available to individuals living inareas which had been put on epidemiological maps beforehand. The Lunsar team was functioning well and

distributing

ivermectin

in

the Rokel and Pampana

river

basins.

2.1.2.

Mobile treatment

This

mode

of distribution

was

carried out by

NGO-supported

teams. The

Bawku ophthalmological team in _Ghana, whose objective ^was to treat ocular diseases

in

the villages, could be

cited. During their

visits, the team could undertake large-scale ivermectin

distribution if

the clinical results obtained

in

the zone allowed

it.

The Bawku ophthalmological team was supported by CBM and carried out missions

in

the Yendi area

in

northern Ghana.

The VCU teams that distributed ivermectin in certain villages during their routine missions formed part

of

this category.

2.1.3

Pessivetreatment

This form

of

treatment was undertaken in fixed health centres, health posts or hospitals in the Programme area. Those responsible

for

^passive treatment were medical officers

or

nurses; they were normally State employees or supported by an NGO, e.g., Philafricaine Suisse in Guinea.

Passive distribution was mainly carried out in hypoendemic areas not included in large-scale

distribution.

The decision

to

treat

an individual

was based

on either clinical or

parasitological diagnosis. This mode

of

ivermectin distribution concerned a small proportion

of

the total number

of

persons treated.

2.1.4.

Communitytreatment

Community treatment was introduced recently

in

certain parts

of

the Programme area, particularly _in

Mali.

This new approach to the distribution laid emphasis on community participation.

Persons who could read and

write

(usually

in their

local language) were selected

by the

villagers themselves and were responsible

for

the distribution.

The supervision

of

such persons was carried

out by

the local

fixed

health centre

or

the nearest

one.

Such a mode

of

treatment could be supported by an NGO, e.g., Sight Savers

in

Mali.

The advantage

of

this mode

of

distribution was that

it

allowed all ^persons

in

the village to be treated once per

year.

Pregnant women could be treated

after

the

childbirth

and

after

the

first

week of breastfeeding; temporary absentees and immigrants from endemic onchocerciasis areas could also be treated.

These persons were involved only

in

ivermectin distribution and would not have to make any diagnosis. The decision on the

treatment of

these communities was taken

by

national health

officials

on the basis

of

epidemiological maps already prepared.

ocP/EAcl4.2

Page 4

2.1.5.

Other modes

of

treatment

This was an ivermectin distribution which could be on a large scale or on an individuat basis

for

specific research purposes.

An

example was that

of

the Tabe

river

basin in Sierra Leone where

the Medical

Research

Council (U.K.)

was conducting

research. In

such

a

zone, ivermectin distribution would depend on the research protocol and

time-limit for

the carrying out

of

the work.

2.2.

^Results

2.2.1.

Eastern zone and southern extension

In the eastern zone and southern extension, the national teams

of

the six countries (Benin, Burkina Faso, Cote

d'Ivoire,

Ghana, Niger and Togo),

with

the support

of

OCP, carried out large- scale distributions

in

20

river

basins

from March

1992

to

February 1993. Out

of

646,810 ^persons enumerated

in

2,187

villages,443,ll8

were treated, i.e., a coverage rate

of

about 6990;641,701 ivermectin tablets were

distributed.

No serious reaction was noted; however, some minor reactions were recorded

in

the basins where the treatment was being given

for

the

first

time.

No census was taken on the

Kara-Keran-Mo, Oti

and Amou basins because

of

the social unrest; however,

to

the above data should be added 75,262 persons treated

in

193 villages with 105,939 tablets.

Other ivermectin distribution activities were carried

out by VCU

teams and some fixed health centres, notably in Burkina, Cote d'Ivoire and Benin. The NGO, Sight Savers, ^was establishing

itself in

the southern part

of

Ghana

in

order to institute community treatment there; likewise, the NGO,

Christoffel

Blinden Mission, was supporting the Bawku ophthalmological team

in

the Yendi area,

in

northern Ghana.

An

attempt to institute community treatment

in

the Baoule basin was in progress in Cote

d'Ivoire.

[n Benin, the Tropical Institute

of

Hamburg, based in Cove, was treating persons who had se'tled in its zones

of

intervention; in Togo, the NGO,

Aid

and

Action,

had carried out a

one-off treatment.

To sum up, the

VCU

teams,

fixed

centres, NGOs and the communities treated 57,036 persons

with

90,589 tablets.

In

all,

575,416 persons were treated

in

these six countries

with

838,229 tlblets.

2.2.2

^{Western zone}

From March 1992 to February 1993, the national teams

of

the

five

western zone countries

(Mali,

Senegal, Guinea, Guinea-Bissau and Sierra Leone) untertook large-scale distributions

in

26 basins under the supervision or

with

the help

of

OCP. Out

of

708,442 ^persons enumerated

in

3,814 villages,503,5l9 were treated

with

745,473 tablets, i.e.,acoverag,e rateof

7l.l%.

During thisperiod, in Guinea-Bissau, the Rio Corubal basin was treated trice while, in Senegal, the Gambia

baiin

was treated twice.

Large-scale distributions were made by NGOs or

with

their support in ^Senegal (OPC) _and Mali (OPC, Sight Savers); 568 villages were treated in six basins; 154,137 persons were treated with 22E,022 tablets.

^,

^{. Community} treatment covered I

I

basins

in

Guinea,

Mali

and Sierra

Leone.

Out

of

the 213,132 persons counted, 165,470 were treated, i.e., a coverage

of

77.6%; 2E9,552 tabletg _ryere used.

I'11;,.

'.

^-.Mali, Guinea and Sierra Leone carried out passive treatment

in

the

fixed

health centres.

Philafricaine suisse was involved in this

aqiviry

in Guinea. In theso three countries, t5,019 ^persons were rreated passively

with

13E,350 tablets.

NGOs treated 299,690 persons

with

472,403 tablets

in

1,052 viuages

in ll

^basins.

"irrages

*l?.t11:,llothe

^western

zone,908,l45

persons were treared

with

r,40r,396 tabtets;4,9g2

Table

l:

@P/EAC|4.2

Page 5

To sum up, Table

I

shows, by country, the number

of

^persons treated and the number

of ivermectin

tablets

distributed. On the whole,

1,483,561 percons were treated throughout the Programme aret, 2,239,625 tablets were distributed.

OCP map

I

shows the zones where large-scale distribution ^was carried

out.

The new basins added are the following:

-

^the Kolente, in Guineq

-

the Baoule, the Black

Vola

and the upper Comoe, in Cote d'Ivoire;

-

the Mouhoun, at the Poni, Pouene and

Koulbi

tributaries,

in

Burkina Faso;

-

the continuation

of

the Black Volta above Bui, in Ghana;

-

the Mono, the Yoto, the Zio and the Haho, in Togo;

-

the Mono, the

Kouffo,

the middle Agbado-Zou, the

Adjiro

and the Terou,

in

Benin.

Summery table

of

lvermectin dlstribution comprising

ell

strategies, modes and rctors

ln

the

1l

OCP countrles durlng thc perlod

of

March 1992 to Fcbruery 1993

Country

Number

of

persons treated

Number

of

tablets used

Burkina Faso

Mali

C6te d'Ivoire Ghana Togo Benin Niger Cuinea

Senegal

Guinea-Bissau Sierra Leone

19,E88 282,40E 235,954 49,848 169,907 99,812

7

t34,233 50,463 35,143 405,E9E

29 900 407 243 326 006 69 939 283 807 128 564

l3

rE3 904 97 ⁷²² t25 435 58? 092

Total 1,4E3,561 2,239,625

2.3 2.3.1

Impact

of

lvermectln on onchocerclasls transmlsslon Results obtalned ln Guinea-Blssau

Following the recommendation made during the

l99l

Annual lnternal Technical Review Meeting,

a

study

on the

impact

of

ivermectin treatment (three times/year)

on

transmission ^was conducted

on

the

Rio

Corubal at Cade, Cabuca, Cheche ahd

Queue. This

^zone benefitted from ivermectin _treatment

in

December 1990,

May l99l

and March 1992.

lt

^was important to note that

two

treatments were made

at the

beginning

of the

study

and that

there was

no

entomological surveillance on the Rio Corubal from January to October 1991.

Despite the lack of consistent baseline entomological data, the entomological resuls recorded

from

November

l99l

to October 1992 seemed to indicate an impact

of

ivermectin on transmission which was reflected in a reduction

in

infective females

of

about 50% at Cabuca and 3O% at Cheche.

Because

of

these meag,re results the interpretation

of

which did not allow conclusions to be

drawn,

it

was recommended that a select committee be set up to decide on the need to continue the study on the impact

of

ivermectin on transmission in the same area or in other localities to the north

of the

Programme's western extension where chemotherapy was the

only

onchocerciasis control method.

It

was observed that

after five

consecutive annual ivermectin treatments, the _Beometric mean

of

the

microfilarial

load which was 4E.4

mf/s

had fallen to 2.9

mf/s

in a cohort

of

268 persons.

Thus, before the sixth treatment, ^a reduction of 49.7% was obtained, compared with the level reached at the

fifth

treatment, and a reduction

of

94.1% compared

with

the pre-treatment _level

(Fig.l).

ocP/EAct4.2

Page 6

2.3.2. Observed end predlcted epidemlologitd trend efter flve lvermectin treetments et ^Asubende

ln

Ghene

The pre- and post-ivermectin treatment epidemiological evaluations in three villages in the Asubende area

in

Ghana were continued

in

^1992.

On the basis

of

these data, an analysis was made, in collaboration

with

the epidemiological modelling team in the

Universityof

Erasmus, Rotterdam, with a view to putting forward assumptions

on

the long-term

effect of ivermectin.

By including also

in

the analysis the

effect of

the vector control carried out at the same time ^as the ivermectin treatment,

different

conclusions were reached.

The new analysis showed that the adult worms gradually became productive again over an average period

of

nine months but no longer reached their pre-treatment productivity threshold. ^Because

of

the

fact that

the drug

did not kill

the adult wormr this permanent decrease

in

the production

of

microfilariae after each treatment was estimated to be 33% compared

with

the previous treatment.

Through these new assumptions, the simulations made

by

means

of

the epidemiological modelling had enabled the adjustment

of

the observed data (prevalence and

CMFL)

to be made, as

shown

in Fig.2.

2.3.3.

^Long-term predictlons

The meeting was informed

of

the results

of

epidemiological modelling on the predictions

of

the impact

of

the long-term use

of

ivermectin.

Figure 3 shows the impact

of

the annual ivermectin treatment in ^a village which was highly endemic with a CMFL

of

about

7l mf/s.

The simulations suggested that an annual treatment would not succeed

in

eliminating the parasite

in

a strategy based on a

time-limit of

^less than 25 ^years.

2.3.4

Results obtained when ivermectin dlstrlbutlon and vector control are comblned

The comparison

of

the results obtained

in

the

original

Programme area

with

those

in

the western extension area in Guinea had allowed a judicious eviluation

of

the impact

of

vector control combined

with

ivermectin treatment on the transmission

of

onchocerciasis. This comparison ^was related to three catching points in Guinea studied before treatment and then three and four ^years after larviciding plus ivermectin, and five catching

poins

_in the original area studied before treatment and then

four, five

and six ^years after larviciding alone.

Using the number of infective larvae per 1,000 parous _as the evaluation criterion, a decrease

of

^77% in the number

of

Lr-head per 1,000 parous was obtained for Guinea and 2l%

for

the original atea, thereby showing clearly the considerable impact

of

ivermectin on onchocerciasis transmission.

In

other words, while only 24 parous females were needed to obtain an

infective

larva

in

Guinea

before the

treatments, 105 were needed

three to four

years

after larviciding

combined with ivermectin. On the other hand, while before treatment

in

the original area,

l5

parous females were needed to get one Lr-head, only

2l

^were needed after

four

to six ^years

of

^vector control alone.

2.3.5

Predictlon

of

the lmpact

of

lvermectln treetment comblned

with

vector control

The simulations were made by using epidemiological modelling to evaluate the impact

of

ivermectin treatment combined with vector

control.

Figure 4 shows the results

of

the simulation

for

two hypothetical situations. Both concerned a hyperendemic village of .the Tiercoura type whose pre- control CMFL ^was about

7l mf/s.

Furthermore,

it

^was supposed that a vector control whose efficacy was 100% had been carried out throughout the period considered. The first diagram shows what could happen during and after a strategy of ten ^years of vector control combined with an annual ivermectin

ocP/EAcr4.2

Page 7

treatment. The strategy seemed to be ineffective and led to recrudescence.

In

the second diagram, the extension

of

ivermectin

distribution

up

to l5

^years seemed, however, to result

in

a much more effective strategy but a sensitivity analysis on the duration required was necessary.

It

was recommended to continue

with

these simulations, including

all

the available results

and taking into

account

the

trends

in the different

parameters considered, such as

the

rate

of

coverage, the duration and frequency of the treatments and the action of the drug on the adult worms.

2.4

2.4.1 Impect on the evolutlon

of

ocular leslons

The resuls of ophthalmological examinations carried out

five

^years after the start of annual ivermectin treatment

in

the Asubende area were compared

with

the baseline data to determine the medium-term evolution of ocular onchocerciasis. It was noted that, in the cohort, living microfilariae in the cornea had been eliminated completely and that the

microfilarial

load

of

the anterior chamber

of

the eye had reduced

from

the geometric mean value

of 3.t

to

0.1. It

^was noteworthy that

it

took

l0

^years

of

vector control

to

observe

similar

results

in

other

localities.

However, the results

for

Asubende were due

to

the combined action

of

ivermectin and vector

control. The

regression

of

lesions

of

the anterior ^seg,ment (iridocyclitis and sclerosing keratitis) was

significant.

With regard to the evolution

of

ocular lesions

of

the posterior segment, no significant change was noted.

2.4.2.

^Impect on morbldity

A study on the impact

of

ivermectin on morbidity was conducted

in l0

villages in the basin

of

the Kaba and

of

the Mabole

in

Sierra Leone and

in six

villages

in

the Sassandra basin

in

Cote

d'lvoire. In

these countries, two groups

of

villages were selected

for

the

trial. A

_Broup

of

villages received ivermectin and the other group a placebo (mebendazole). Questionnaires were given to the villagers and concerned their knowledge and

ability

to recognize the symptoms of onchocerciasis and

their

perception

of

the effects

of the treatment.

The study was

in

^progress and the group that received the placebo would be treated

with ivermectin. After

this second phase the data analysis would be madp.

The preliminary

analysis

of the resuls of the study

revealed,

in

^general,

a very

low knowledge

of

onchocerciasis (vector, disease and treatment).

The meeting was informed

of

the results

of

a study carried out

in

Malawi,

with

financial support from

TDR,

on the action

of

ivermectin _on skin lesions.

After the

ivermectin treatment,

a

marked improvement wils noted

in the skin

^lesions;

however,

for

some lesions improvements were observed also

in

the group that received the placebo.

The

study showed the

difficulties that could

be encountered

in

the evaluation

of

the

effect of

ivermectin on skin lesions and that

in

such studies

it

was important to have a control group treated

with

placebo.

2.5.

Research on effects

of

long-term use

of

lvermectln

Research on the effects

of

long-term use

of

ivermectin could be envisaged in the following

areas:

-

^parasite resistance;

- ^effect of

ivermectin on the adult worm;

- ^effect

on the epidemiological situation;

-

^long-term adverse effects on the ^users.

Impect

of

lvermectln on the evolutlon

of

ocuter leslons and other forms

of

morbldlty

@P/EACI4.2

Page 8

2.5.1.

Pereslteresistance

Ivermectin ^was introduced in veterinary medicine well before its use in man and resistance to this product had been reported

in different

^parts

of

the

world in

animals. Studies

in

laboratory showed resistance

of

'Haemonchw contotuts a;nd

Trichostongfus colibrifomis to

ivermectin.

Resistance to ivermectin could therefore be a possibility

in

man.

Research was currently being conducted to study parasite resistance: (a)

!U!yg,

^{taking into}

account changes

in

the

microfilarial

load

in

treated patients; (b)

in vitro in

larvae

of

O. volwthu; (c) by computer simulations, taking

into

consideration data on O, votwlus and those concerning other parasites already resistant to ivermectin.

2.5.2.

^Effects

of

lvermectln on the edult worm

The objective

in

this case was to ascertain the effect

of

a long-term use

of

ivermectin on thg adult

worm. It

was now known, that ivermectin temporarily paralyzed the muscles

of

the uterus

of

the adult worm, halting the production

of microfilariae.

Nodules had been taken

from

^patients treated many times at Mako ^(Senegal) and Asubende and sent to laboratories

for

a histological study.

2.5.3 ^Effect

on the epldemlological sltuatlon

This effect could be evaluated periodically by means of results collected from skin snips (see

section 2.3.2. for the Asubende results). This evaluation would be continued seven and ten ^years after the consecutive annual treatments at Asubende. More generally, in any zone where ivermectin ^was distributed, the evaluation would be made every

five

^years

with

a view to assessing the long-term effect

of

ivermectin on the epidemiological situation.

2.5.4

Long-term slde-effects on patients

For the moment, ivermectin has had no teratogenic effects on livestock and other domestic animals

in

gestation that had received doses three times higher than the normal ^dose.

The pharmacodynamic effects of ivermectin were well known:

only

l%

bf

the product was eliminated

in

urine, its

half-life

was 12 hours and

it

metabolized

in

three ^days.

ln

conclusion,

the

long-term effects

of

ivermec(in

could

be monitored

in the field

by organizing,

in

health centres and health posts

which

regularly used this product, data collections which would make

it

^possible to detect any anomaly related to the prolonged use of the

drug.

^Persons who would present special signs could then undergo detailed examinations.

In areas where ophthalmological examinations were carried out periodically, any anomaly concerning the prolonged ^use

of

ivermectin would have to be the subject

of

more in-depth studies.

3.

EPIDEMIOTOGICAT EVALUATION

3.1.

^New epidemiological evaluation strategy and ^prospects

Because

of the distribution of ivermectin, it

^was

^important that the

epidemiological evaluation techniques previously used by OCP be re-examined.

At

^present,

four

possi.bilities could be envisaged

in

the Programme area:

Sltuation l:

^Areas

that had

undergone successful vector

control for

14 years

and

where the prevalence

of

infection, as diagnosed

with

the ^use

of

the skin snip, was zero

or virtually

zero. Such areas were subjected

to

epidemiological surveillance

in

an

effort to

detect

any

recrudescence or infection in the cohtext of devolution. In this case, the best means of detection

of

recrudescence was serology;

in

the absence

of

that, skin snip could be used.

ocP/EAcl4.2

Page 9

Situation 2:

^Areas

that

^were

still

undergoing

larviciding

alone

and

where

the

prevalence was

continuing to

drop.

In such areas, skin snipping could be used

for

the epidemiological evaluation.

Situetion

3:

Areas where only ivermectin treatment ^was being carried

out.

^In such areasr skin snip,

for

the monitoring

of

the decrease in prevalence, and ophthalmoligical examination

of

patients could be used.

Sltuetion

4:

Areas where both larviciding and ivermectin treatments were being carried

out.

In such areas, skin snip and ophthalmological examination could be ^used

for

the monitoring

of

^{patients and}

serology

for

the detection

of

new infections.

During

the meeting, the Programme Director asked that a group _should study

this

new epidemiological evaluation strategy; a report would ^be prepared and submitted to the Expert Advisory Committee.

3.2.

Consequences

of

large-scale lvermectin

dlstrlbution on

epidemiological evaluation

of

vector control

The method

of

epidemiological evaluation

of

the vector control activities in OCP, was the three-yearly epidemiological surveys carried out

in

the indicator villages.

In addition to this

cycle

of

epidemiological surveys, there were surveys undertaken in specified areas to help

in

the decision-making on whether

or

not larviciding could stop.

The third category of epidemiological evaluation ^was what obtained in the extension areas, or other marked-out ^areas of the Programme where both ivermectin distribution and larviciding were undertaken.

3.2.1

Measurement

of

^prevalence

At

present, the epidemiological evaluation depended mainly

on

the use

of

the skin snip which made

it

possible to assess the prevalence and the community

microfilarial

load (CMFL).

This type

of

evaluation

of

vector control was

only valid in

areas where the

only form of

control was

larviciding. It

was, therefore, used

in

the

river

basins

in

the

original

Programme area,

in

the zones which were not under ivermectin treatment.

The decision as

to

^whether

larviciding

could stop

in

a

particular river

basin was ^based especially on the epidemiological situation

in

the area concerned.

It

was therefore crucial that the parasitological findings obtained

from

evaluations

in

such basins reflected the true picture

of

the situation without any influence

from

ivermectin use.

3.2.2,

Measurement

of

lncidence

In the extension areis or areas

within

the original area where OCP applied both ivermectin and larvicides, the epidemiological evaluation became complex because

of

the short-term effect

of ivermectin. In

such situations the

only

way to assess the impact

of

vector control combined with ivermectin

on

transmission was the measurement

of

the incidence

of infection. It

was therefore essential that a cohort

of

negatives be periodically monitored parasitologically (skin

snip). It

^was

important not to give ivermectin to such individuals who should receive only ^placebos.

3.2.3.

^Serology

The way to minimize the

difficulties with

the evaluation

of

^vector control

in

the ^presence

of

the widespread use

of

ivermectin was

to

have a diagnostic tool capable

of

detecting ^prepatent infections or better

still

parasite antigens.

nt

the moment the

tri-cocktail

antigen appeared ^promisinB,

for

the detection

of

^prepatent infections

in

the young ag,e group.

ocP/EAct4.2

Page

l0

Research was

in

^{progress with} a view to the development

of

a polymerase chain reaction (PCR) methodology, for the detection of parasite antigen, which would make

it

possible to reveal any onchocercal infection.

3.3.

Immunodlagnosls: Development

of

a serologlcal test

As ^part of the

research supervised

by the

immunodiagnosis subcommittee

of

SC/FIL (Steering Committee/Filariasis), considerable progress

had

been made

in the

development

of

immunodiagnostic tools

for

the detection

of

onchocercal infection.

During its last meeting on

l5

March 1993, the subcommittee concluded that the results

for

the

tri-cocktail of

the antigens Ov7, Ovl

t

and

Ovl6

were promising enough to

justify

its large-scale testing in operations planned in the Programme area.

It

^was therefore proposed to undertake ^a pilot study between

April

and October 1993. The objective

of

the pilot _study was

two-fold:

To obtain an operationally meaningful estimate

of

the specificity

of

the

tri-cocktail.

This would be done in a large sample

of

children

from

the central OCP area who ^had never been exposed to onchocerciasis infection.

To

confirm

the sensitivity

of

the

tri-cocktail

antigen in detecting patent infection, as

shown against the sera

from

the village

of

Pendie.

To attain

these objectives, blood samples

would

have

to

be taken and

specificity

and sensitivity tests carried out.

For the

blood collection, the age group selected was that

of 5 to

15

years. The

blood collection would _{be on}

filter

paper through

finger-pricks.

Analysis would be done by ELISA, and

for all

sera the Optical Density (OD) values would _be recorded. The

filter

^papers would then be stored

dry

and refrigerated after analysis

for future

reference.

A consultant ^was expected

in

Bouake in June 1993

for

the training

of

staff and the setting up

of

the laboratory which should be operational

in July

1993. During the

pilot

study, serological testing would be undertaken in parallel in the reference laboratory in Basle. In addrtion to this study,

SC/FIL

recommended that blood collections be made

with

the view

of

having reference collections

from

villages where recrudescence

of

onchocercal infection could theoretically occur.

3.4.

Ophthalmological evaluation

The objective

of

the ophthalmological evaluation was to determine the impact

of

vector control on ocular disease.

Indicator villages

in

which the communities had a.high level

of

infection would therefore have

to

be selected. These villages should be representative

of

the

river

basins, ensuring a goo(

sampling.

.

Emphasis should be laid on the maintenance

of

standardization

of

data collection and the Czifryttig out

of

regular quality

control.

The periodicity

of

the examination should be long enough

16 elldin the measurement

of

any change

in

the ocular lesions. This periodicity was that used

in

the ffg..gq.inttg.at the time when larvicideJalone were ^used, i.e., three, five, seven, ren and.rwelve ^years

iittbr

ttie Stdrt

of

the control measure.

l,-

i. .rrn.:e(:r,in sotthern Sierra Leone, eight villages had been selected

for

the evaluation

of

control by i.v.efnqSLirl treatment

alone. [n

Guinea, ten villages

in six river

basins had been selected

for thl

e,yaluatio.n of vec0or control combined with ivermectin treatment. In the original area,

it

was plalned

tgfhooss l3 ^villaies

that had been regularly monitored

in

order

to.evaluite

the impact

oi

voctot control after 20 years

of

larviciding.

ocP/EAcl4.2

Page I I

3.5.

3.5. r.

Definitive cessation

of

larviciding

in

the

origlnal

Programme area Recent epidemlologlcal results thet could help ln declslon-making

Map 2 shows the basins under larviciding in

OCP.

The basins in the original area that were concerned

with

these latest evaluations were the White Bandama and the Comoe in Cote d'Ivoire, the lVhite

Volta in

Ghana and the Black Volta

in

Burkina Faso, Cote

d'Ivoire

and

Ghana.

The White Volta had been under larvicidi;rg since Januaty ¹⁹⁷⁶ and the lVhite Bandama and Black Volta ^since February 1975. The section of the Comoe which ^was evaluated had been under treatment since March

t979.

(a)

_{lYhite Bandema}

The raw prevalences observed recently

in this

basin ranged between 0.0% (Bissidougou, Dickodougou, Oureguekaba) and 23.1% (Tchebrou).

The epidemiological situation ^was, on the whole, good in the areas located upstream from

the

confluence

of ^the Bou-lVhite

Bandama (prevalence less

than 5%

everywhere

except

at Nabediakaha where

it

was 7.4olo).

It

was markedly less good

in

the localities found downstream

from

this confluence.

A

human migration study (results currently being analysed) carried out concurrently with the above-mentioned evaluations indicated the existence

of

an intense migratory movement

in

the lVhite Bandama basin.

(b)

rVhlte Volta

The raw

prevalence obtained

on this

basin showed a satisfactory situation

with

figures ranging from 0.0% (Duu) _to 2.1% (Mushuo).

(c)

.Black Volta

Evaluations made on both sides

of

this watercourse (Ghana and Cote

d'Ivoire)

revealed a

satisfactory

situation

(prevalence less

than

5%

everywhere). On the Burkina side where

the epidemiological evaluation had not yet been completed, a replacement village presented a prevalence above

l0%.

The meeting recommended that investigations be continued on this part

of

the Black Volta

in

Burkina Faso and that ivermectin treatment be instituted there.

(d)

_Comoe

On both banks

of

this watercourse (from Toumbo to the confluence

with

the Diore), almost

all the

prevalences observed were above 5% and between l0% and 20%

in

most

of ^the

^localities

visited.

The resuls showed an unsatisfactory situation on this reach

of

the Comoe where juvenile infections (low loads) and heavily loaded adults were found.

(e) Kuntuli

focus on the

Oti

The investigations conducted

within

a radius of about

l5

km around the village

of Kuntuli

showed a certain complexity

of

the epidemiological situation in this focus. The prevalences observed were low on the Togo side (Oti-village: 0.0%; Bonwido: 1.7%) and higher on the Ghana ^side (Nakwu:

10.2%; Gnalajodo:

l2.l%)

in the localities visited on the Kulaw (small right-bank tributary of the Oti).

Because

of

the cessation

of larviciding on

the

Oti,

these villages

would

have

to

be treated with ivermectin.

ocP/EAct4.2

Page 12

3.5.2.

Plan

for

definltlve cessatlon

of

larvlcldlng

ln

the

orlglnal

Programme area

The epidemiological results

of

the lVhite Bandama had made

it

^possible to envisage the

definitive

cessation

of

larviciding on the reaches located upstream

from

the Bou confluence.

The decision to stop larviciding on some reaches

of

the Comoe, the Black Volta and the White Volta basins would be taken during the year after an in-depth analysis

of

the epidemiological data.

3.5.3.

^Plannlng

of

future epidemlologlcal evaluatlon actlvlties

With a view to intensifying the collection

of

epidemiological data necessary

for

decision- making on the

definitive

cessation

of

larviciding

in

the original Programme area, future _evaluation campaigns would be carried out on the

N'zi

basin in C6te d'Ivoirer on the Daka in Ghana and on the Bagoe and the Baoule

in Mali

where the situation observed

in

1992 was not completely satisfactory.

It

was also planned to make an evaluation on the

Alibori,

the Mekrou and the Pendjari.

3.6.

^{Human mlgratlon} studles

3.6.1.

^Infected migrants and

rlsk of

recrudescence

The simulation of the risk of recrudescence following the arrival of many migrants in a zone where vector control had made

it

^possible to reduce the prevalence to a very low level showed that in a Tiecoura type

of

village

with

a pre-control CMFL

of 7l mf/s,

where the population was about 200 inhabitants and the

biting

rates high, even a small number

of

infected immigrants could lead to a high

risk of

recrudescence. The

risk

depended on the

microfilarial

load

of

the

migrants.

This showed the importance

of

the ivermectin treatment

of

any migrant settling

in

the cleared zone.

3.6.2.

Studies carrled out recently

The most recent human migration studies were those conducted

in

the Kulpawn basin in Ghana (February _{1993) and}

in

the White Bandama basin (March 1993). The analysis

of

the resulrs was

in

^progress.

4.

^DEVOLUTION

4.1 Institutional

framework _{and roles}

of

the principal actors

The principal _actor in the implementation

of

the devolution ^process in a country remained the country

itself.

To help the countries in their tasks, a number

of

institutional organs or structures had been or would be put in place. Thus, on the recommendation

of

the JPC

of

December 1992, the document

defining

the institutional framework and roles

of

the

principal

actors was revised and presented to the meeting ^(see document9S/l15/devo/2.17, March 1993 and Table attached as Annex 2). The meeting ^was also informed of the holding of another meeting after that of the annual internal technical review

for

detailed discussions on some aspects related to the roles

of

the principal _actors, the epidemiology

of

onchocerciasis and data analysis.

4.2.

Proposed entomological surveillance

ln

the context

of

devolution

In the devolution ^plans prepared by the Participating Countries, the only activities selected were epidemiological surveillance, centred

on

parasitological surveys

(skin

snip), and ivermectin treatment of onchocerciasis patients. Currently, the parasitological surveys were encountering, more and more, a number

of difficulties,

the main ones being:

a decrease in the sensitivity

of

the skin-snip technique because

of

the treatment

of

the populations

with

ivermectin which reduced the

microfilarial

load

in

^persons treated;

reluctance

of

the populations to accept the skin snip;

ocP/EAct4.2

Page I 3

absence, at the moment,

of

a reliable technique

for

the early detection

of

a ^possible recrudescence

of

infection.

Because

of

these remarks, the possibility

of

introducing entomological surveillance into the devolution ^plans

of

the Participating Countries was raised. This entomological surveillance should be much simplified so that it could be used by the national teams. It could ^be envisaged in the former hyperendemic areas. The technique would consist

in

making villagers catch the blackflies, making partial parous-nulliparous dissections and looking

for

the larvae of O. volvnlus only in the head of the parous blackflies.

The interpretation

of

the data

by

the onchocerciasis transmission epidemiological model (ONCHOSIM) would probably enable any possible recrudescence

of

the disease to be detected.

The meeting

recommended

that a

select committee should

study the possibility of introducing

entomological surveillance eventually

into the

devolution plans

and

make concrete proposals.

4.3.

Support

of

OCP

rnd

IYHO/AFRO to devolutlon activities

in

the Particlpating Countries

4.3.r

^OCP

On the basis

of

the entomo-epidemiological results, OCP had selected and made available

to

the seven countries

in

the

original

Programme area,

for a

^period

of

^{three years,}

a list of

¹⁷⁷

sentinel villages as

part of

the epidemiological surveillance together

with a

map indicating their geographic location (Map 3). This list ^was not exhaustive; the countries could add other villages. The meeting urged the

different

countries to look actively for other sources

of

funding, apart from OCP,

for

the

carrying out of

these epidemiological

surveys. In addition to

these activities, OCP ^was assisting the Participating Countries technically in the preparation or update of their devolution ^plans (see report

of

meeting between OCP and National Coordinators

for further

details).

lVith regard to ivermectin distribution, OCP was intervening by giving technical and logistic supporq

it

was participating

in

^practical

training in

the

field during

ivermectin

distribution

and epidemiologiial evaluation and in advanced training and refresher courses organized by the countries

(Benin).

OCP was helping

actively in the training of

^villagers

and in

establishing community treatments, was participating in consciousness-raising at all levels by organizing forums, speaking at conferences and giving radio interviews, and was maintaining contact

with

NGOs,

inviting

them to get involved in all devolution activities, notably ivermectin distribution.

4.3.2.

^WHO/AFRO

The participation

of

WHO/AFRO

in

the setting up

of

the intercountry devolution support and monitoring ^process concerned technical and financial support.

4.3.2.1.

Technlcal support

(a)

Training

of

health personnel on human trypanosomiasis, schistosomiases and Guinea worm or dracunculosis

(in

Burkina Faso and Niger).

(b) The putting at the

disposal

of

^WHO Representatives

in the

eleven Participating Countries, in June 1992, of a set of ten modules for the organization of district seminars according

to the

problem-solving teaching method (Prldagogie

par

Rrisolution des Problimes).

(c)

Making available to National Coordinators a 30-parameter form

for

the monitoring

of

devolution activities extended to other diseases.

(d)

The sending to WHO Representatives and National Coordinators

of

an outline

for

the implementation of devolution as part

of

the scenario

for

health development in Africa.

ocP/EAct4.2

Page 14

(e)

Missions to three countries in the original area

for

advice with a view to the update

of

the devolution plans and the setting up

of

national committees.

4.3.2.2.

Flnanclal support

The country budget programming (AFROPOC), amounting to some US $ 50,000, ^{was used}

for

the training

of

health workers and the organization

of

consciousness-raising days on devolution extended to the control

of

other diseases (trypanosomiasis, schistosomiases and Guinea worm).

4.4

^Mall's tonsclousness-raising committee

A

survey conducted

in

the

Banifing IV

and Baoule (Bougouni) basins revealed that the populations had very limited knowledge of onchocerciasis. This deficiency motivated the setting up

of

a consciousness-raising committee

in

the western

zone.

This committee set as its objective the preparation

of

a simple and functional strategy

with

a view

to

^getting across

to

the villagers the message on onchocerciasis and ivermectin treatment

in

the whole

of

Mali's onchocerciasis zone.

The messages

to

be disseminated were the information

of

the target populations on the symptoms of the disease, its transmission, OCP activities, the return

of

uninfected blackflies after the cessation

of larviciding,

ivermectin treatment, the impact on individual and community health and the socioeconomic impact.

This committee was collaborating closely

with

NGOs involved

in

ivermectin distribution so that they would include public awareness (information, education and communication)

in

their

field activities.

The means used

for

^getting the ^message across were forums

with

the villagers and the use

of

the

prlnt

media and radio.

This experience

in

Mali could be spread later to the other OCP countries.

5 RESULTS OF VECTOR CONTROL AND VCU RESEARCH

5.1.

Entomological evaluation (March 1992 to February 1993)

In the original area, about 94% of the catching points had an Annual Transmission Potential (ATP) below 100; six points had an ATP slightly above 100.

In the southern extension in Ghana, Togo and Benin, the transmissions recorded were due to forest females, viz., S. soubrense Beffa form, S, yahense and S.squamosum. In Cote

d'Ivoire,

the Kongasso catching point (Marahoue) had an ATP

of

^129.

In the western extension, in Guinea, only six points had an ATP slightly greater than 100.

The transmission at five

of

these points was due to forest females. In Sierra Leone, in the area under

larviciding,

I

I

^points had an ATP above 100; the transmission

at

these points was entirely due to forest females.

On the whole, the entomological situation was good throughout the Programme area. For the savanna females, only eight points had an ATP above 100.

5.2.

Summary

of

post-control _studies

The post-control studies were aimed

at

proving that the parasite had disappeared

in

the vector, S. damnosura s.1., after showing epidemiologically that

it

had disappeared in man. Below the threshold

of

one infective female per 1,000 parous, larviciding could be

definitively

stopped.

ocP/EAcl4.2

Page 15

POST.CONTROL STUDIES 1991 - 1992- 1993

Results

The results obtained were excellent at Nabere and Zambo on the Bougouriba (0.39 and ^0.61 infective females per 1,000 parous), Pont Leraba (see Fig. 6b) on the Leraba (0.50 infective females

per

1,000 parous! Ziou-Zabre and Nangodi on the Red Volta (0.49 and 0.65

infective

females per 1,000 parous), and Zongoiri-rapids on the White Volta (1.17

infective

females

per

1,000 parous).

Because

of

these good results, larviciding and blackfly catches had been

definitively

stopped on the Bougouriba,

the

Leraba, the Red Volta and the lYhite Volta upstream

from

the Zongoiri-rapids.

Before the beginning

of

OCP activities, the number

of

^infective females on these watercourses ^was E0-100

per

1,000 parous. The situation was satisfactory at Badikaha on the White Bandama ^(1.08

infective

females

per

_1,000 parous).

Larviciding

had been suspended on the reaches

of

the White Bandama above the confluence

with

the Bou.

The results obtained at Batie ^(see Fig. 6a) on the Bambassou, a tributary

of

the Black Volta (3.81 infective females per _1,000 parous) and at Keremou on the Mekrou (3.12 infective females per

1,000 parous) were not satisfactory, hence the resumption

of

larviciding on these rivers.

Post-control studies were being continued at Porga and Bukasu on the

Oti.

^A post-control study ^was envisaged on the Banifing

IV

in

Mali in

¹⁹⁹³ during the transmission period, with a view

Points (River)

Period Number

of

parous females dissected

Number

of

females with

L3 in

^head

Number

of

infective females

per

I,000 parous flies.

Situation Pont Leraba

(Leraba)

from 03.01.91

to 2E.02.93 21,679

ll

^0.50Good

Zrmbo

(Bougouriba)

from

^13.06.91

to 31.12.92 17,E66

n

^0.6tGood

Bukasu

(oti)

^January

1992

to 2l -03-93 3,714 ²

0.54 (Study in progress)

Panseni

(oti)

January and

February 1993 2,839 0

0 (Few

blackflies) Bailikaha

(White Bandama)

mid-January to mid-June

l99l

January to September 1992

20,335 22

1.08

Acceptable

Keremou (Mekrou)

from 6-07-92

to 6-08-92 4,1 65

l3

3.12 Bad.

Resumption

of

larviciding Batie

(Bambassou

tributary of

Black Volta)

24-08-92 to

20-t0-92

^{5,237 20}

3.81 Bad.

Resumption

of

larviciding

ocP/EAct4.2

Page 16

to collecting infective larvae

for

identification by

DNA

^probe 5.3.

5.3.1

Larviciding and eerlel operations Insecticide use

The rotational use of insecticides was applied on all the rivers with a few changes according to the hydrological regime and/or ^prospects

of

resistance.

During the dry ^season, at low waterr B.t. H-14 was

virtually

the only insecticide used, with larviciding suspensions as soon as the entomological situation allowed it.

During the rise in water level, the maximal productivity of the breeding sites did not permit any suspension, whose duration would ^be too long, and necessitated the use of only attack insecticides

which offered

less prospects

of

resistance compared

with the other compounds. This

mainly concerned pyraclofos, knowing that at these discharges

of

the period

of

rise in water level, the other products

could not be

used because

of the risk of

resistance

(Abate), toxicity

(permethrin, carbosulfan) or cost-effectiveness

(E!.

H- l4).

At high water, larviciding could be suspended as soon as the entomological situation allowed

it,

and classically the

following

rotation was used: permethrin/Abate/carbosulfan/Abate.

During the flood-subsidence period, at the end

of

the rainy season, the productivity

of

the breeding sites increased again and larviciding could no longer be suspended. Abate and pyraclofos were then used preferentially _up to the

dry

season when

BL

^H-14 appeared again.

In

1992, some 11,300 km

of river

(233 reaches) were treated

in

the western zone, which represented insecticide consumptions roughly similar to those of the previous year, with the exception

of

B.t. H-

l4 for

which an additional consumption of 84,500 litres became necessary in order to make up

for

the poor performance

of

the

l99l

and 1992 batches.

In

the eastern zone, the six operational insecticides were used and they gave good results.

The

insecticides used most were

Abate, phoxim and, particularly,

pyraclofos'whose quantities consumed were double those

of

the previous ^year.

Ground larviciding, although negligible compared .with helicopter larviciding, constituted an indispensable support to aerial larviciding and was carried out mainly

with

B.t. H-14 and Abate.

In

terms

of

cost

of

aerial larviciding, the calculations showed that the sum

of

US $40 per kilometre

of river

treated represented a threshold beyond

which

helicopter

larviciding

operations became too costly.

If

the toxicity

of

the compounds used on the non-target fauna was also taken into account,

it

^would give a range

of

use that would provide some surprises compared

with

the classic standards

of use.'Thus,

carbosulfan could be used reasonably

only

between 70

and

150 m3/sec.

although this

limit

could be exceeded exceptionally because

of

the fact that

it

was the only carbamate in the Programme. Conversely, permethrin could be used at very high discharges and became the only insecticide utilizable beyond 450 m3lsec. which wasi moreover, the upper

limit of

the use

of

Abate.

Although the purchase price

of

pyraclofos was high,

it

could be used between 15 and 300 m3lsec. at a reasonable cost because

of

the low dose used and its great

carry.

B.t. H- 14, on the other hand, had

a very limited

range

of

use (between

0 and

15 m3/sec) because

of its

poor carry and

high

river application dose.

The consequence! at the operational level, was that considerable progress had been made

in

the

field of

help

for

decision-making on

larviciding.

As a matter

of fact, if, in

addition to the problems

of

cost and

toxicity,

the

different

physical and biological parameters

of

the environment were taken into account as well as those related to the insecticide itself and to the conditions

for

its application, the selection

of

the compound most appropriate

for

a given context had been greatly facilitated.

ocP/EAcl4.2

Page 17

5.3.2.

Insecticideresearch

(a)

Reslstance

The situation

of

blackfly resistance to the insecticides had ^been relatively stable since two years. This was largely due to the successful application of rotation of the six operational insecticides.

Phoxim resistance was present

only in

the lower Comoe and lower Bandama basins and

its

level seemed to be regressing. Temephos resistance had appeared mainly

in

Simulium sanctipauli and ^Si damnosum s.s.

in

the two basins already mentioned.

In

the rest

of

the OCP area under larviciding, where the

principal

vector remained Simulium sitbanum, temephos resistance

did

not represent an operational obstacle. Temephos susceptibility

in

Sierra Leone had proved preoccupying

in

recent years because of a gradual decrease. However, a recent mission to the central and north-western ^areas ievealed

a

normal susceptibility to temephos.

lYith

regard to the other insecticides,

all

the points visited in Sierra Leone showed a normal susceptibility.

(b)

Reseerch

ln

^progress

Insecticide research

in VCU

followed a resolutely applied orientation, i.e.,

finding

new formulations and new insecticides that would make

it

^possible

to

increase the

efficacy of

blackfly control while reducing their cost and impact on the non-target organisms.

lVith

regard

to

the chemical insecticides,

the

main

part of ^the

research concerned the selection

of

a non-organophosphorus insecticide that could be ^used

for

a discharge between

l5

and 70 rnP/sec. Two insecticides which formed part

of

a new group, the pseudo-pyrethroids, would ^be tested as a

priority in

1993 because of their efficacy on blackfly larvae and very low

toxicity

on fish.

They were OMS 3002 (Vectron) and OMS 3050. The next trials would cover the

effect of

Vectron on the non-target fauna (crustacea and insects);

if

the results proved positive, operational trials would

be conducted. Concurrently with this

research,

quality control activities on the

operational insecticides were going on;

in

this connection, there had been no incident

in

recent months.

lVith

regard

to Br H-14, the ^new

^{bioassay system}

(orbital

shaker)

had

reached the operational st4ge. Its use, in ^place of the mini-gutter system, would increase significantly the analysis potential

of

the tnsecticide Research

Unit (IRU).

^Further, great progress had been made

in

recent years through collaboration

with Institut Pasteur. It

had, thus, been possible

to

determine the susceptibility

of

the blackfly larvae to the

different

toxins present in

E

^H-

^l4

formulations. These results allowed

it

to be hoped that there would ^{be a} rapid and rational development

of

more powerful B.t. H-14 formulations

for

the control

of

^{blackfly larvae.}

5.3.3.

^{Some lmportant points on aerial operations}

The meeting was informed

of

the progress made

in

the management

of

aerial operations, both administratively and technically. Steps had also been taken

for

better cooperation between the eastern and western zones so as to standardize the methods used

for

the management of data collected in each

of

the two zones. In this connection, an analysis programme had been developed with a view to evaluating the cost

of

larviciding and the amount

of

savings made

from

larviciding suspensions.

With regard to the conduct of aerial operations, the spraying systems were giving complete satisfaction and the relations between OCP and Evergreen Helicopters were good. The new contract covered only the Hughes 500 helicopters.

5.4.

^Results

of

^parasite identifications by DNA ^probes

The

DNA-probe

laboratory, set up a year ago

in

Bouake, ^was receiving samples collected throughout the Programme area. The identification

of

all the

life

^stages

of

the parasite, Onclocerca volwlus, was being made there routinely. Its analysis capacity increased with the assumption of

office

of

an assistant

in

December 1992.