RAPID EPIDEMIOLOGICAL MAPPING OF ONCHOCERCIASIS (RBMO) IN GUERA AND SALAMAT PREFECTURBS, RBPUBLIC OF CHAD*
B. E. B. Nwoke I+; Jo, oye2; N, Kirningar3;GZ,Matchoke 3; SA, Albissaty 3; N, Yotta 3 & NC Kodbaye 3
I Consultant, National Onchocerciasis control Programme, Nigeria School of Biological sciences, hno State University, p M B 2000 owerri Nigeria.
2 Ministry of Health , Project Adviser, Sight Saver lnternational, Bp 47g4yaounde, Cameroon
a J Division Des Maladies Transrnissibles, B P 440 N' Djarnena, Republic Du Tchad.
* This study received financial support frorn WHO African Programme for Onchceciasis control (APOC), Ouagadougou Burkina Faso (ou\lcp\cTD\504\Ap\gs\040\00) in collabration with Organization Pour La Prevention De La Cecite (OpC) paris and Division Des Maladies Transrnissibles, Republic of chad.
u$horq + WHO Temporaray Adviser on REMO and author to IifFIO Correspondence should be whom addressed 2
SUMMARY
ln recognition of the obvious gaps in our understanding of the actual distribution and intensity of
human Onchcerciasis in Republic of Chad, especially in the Southeastern Prefectures of Guera and Salamat, and the urgent need to determine where Community Directed Treatment with Ivermectin
(CDTI) should be implemented as wellas ensure adequate coverage, WHO/APOC sponsored Rapid
EpidemiologicalMapping of Onchocerciasis (REMO) using village onchocercalnodule rate as indi-
cator in Guera and Salamat (February 17 - March 28, 1998) Of the 158 villages selected for this
exercise, 87 (55.06%) of them were examined while the remainingTl (44.94oh) wereeither inacces-
sible (22.15o/o) or non-existing (22.78%). The present result showed that human onchcerciasis is only sporadic in Guera and Salamat Prefectures as only 6 persons from 4 (4 60%) villages (out of the 87 villages examined ) had nodules of onchocercal origin. The disease was absent in96 55% $a) of the villages examined. All factors put together, these sporadic cases may be "cases whose travel
histories or occupational activities in endemic areas suggested that they have acquired their infection
outside" Guera and Salamat Prefecture. These are discussed in the context of the CDTI control strategy.
INTRODUCTION
The issue of onchocerciasis as a serious public health problem in Chad was highlighted by
Buck etal (1969) in which they reported endemic cases in Ouli Bangala and Masidjanga (on the southern sore of Lake Iro opposite Boum Khebir) and Sporadic cases in Ouarai. Earlier in the same area, Von NOORDEM & BUCK (1969) recorded up to 9.0% blindness and 18.60/o corneal opacities as well as 18.5% disfiguring genital/inguinal complications and 61 .lYo damaging skin lesions. BUCK etal (1970) in their book, "Health and disease in Chad: Epidemiology, Culture and Environment in five villages" also hoghlighted human onchocerciasis in Southeastern Prefectures.
In these earlier studies, the Lino river was the only river system in the area where Simulium damnssum complex were caught regularly and where conditions for continued breeding were favourable (BUCK etal, 1970). Other reports on the disease included Ministry of Health (1966), National Research
Council (1966), ZIEGLER (1967). Since these earlier reports, there has been paucity of published comprehensive information on the epidemiology and socioeconomic and cultural impact of the dis- ease in most part of the country. J
In course of the present study, the team discovered that there were a lot of revealing unpublished epidemiological study by Catholic Mission of Bubokum in the Logone Oriental prefecture in l99l and another study by Africare in Logone Oriental, Logone Occidental, Mayo Kebbi, Tandjle and Maye chari Prefecture in 1986-87 and 1993-94. These studies recorded endemic onchocerciasis in most of these prefecture However, all these reports have continued to concentrate in the south- western prefectures of the country with little or no epidemiological information on the southeastern area, except perhaps speculations and extrapolative ideas. The information on the disease distribu- tion and intensity on the southeastern prefectures are none existing or so sparse to the extent that there is at present virtually no guidance on whether human onchocerciasis should be accorded any importance in the ongoing control programmes
The APOC main strategy for onchocerciasis control is Community Directed Treatment with Invermectio (CDTI) And the successful implementation of CDTI is based on comprehensive baseline epidemiological data The absence or limited data on such information makes it difficult for ApOC, Nationals and NGDOS to actually determine the degree/level of endemicity of onchocerciasis for effective CDTI prioritization in the southeastern prefectures, especially in Guera and Salamat where there are speculations of endemic onchocerciasis. It was against this background that Apoc financed this study, in collatoration with oPC Paris and NOTF Chad to generate a comprehensive epidemiological picture of the disease in Guera and Salamat prefectures using the method of Rapid Epidemiological Mapping of Onchocerciasis (REMO).
Materials And Methods
Chad is a land-locked country located in central Africa between Lat.80 and 240N, and Long. 130 and 2408 It has a population of 6,597,852 and a land surface area of 1,2g4,000 sq. km (51.4 inhabitants per sq. km).
Subjected to allvariations of tropical climate, Chad is administrative arranged with l4 prefectures. The present study is carried out in two adjacent prefectures of Guera and Salamat in the Southeastern part of the country (fig 1) Wth a population estimate of 338,046 and headquarters at Mongo, Guera is made up of four administrative Districts: Melfi, Bitkine, Mongo and Malgalme. Salamat prefecture has headquarters at Am Timan. It has an estimated population of 19g,5g3 and three Districts of Abuo Deia, Am Timan andHaraze/Mangueigne. 4
The Districts of Bitkine, Mongo, Malgaline, Abuo Deia, and northern part of Melfi and Am Timan
are with the dry Sahelian bio-ecological zone characterized by slight and irregular rainfall and very
extreme temperatures during the hot and cold seasons. On the other hand, southern Melfi and Am Timan as well as HarazelManguiegne Districts are in the savanna zone.
Drained mainly by Bahr Aouk and Bahr Salamat, most of the villages in the study area are flood plain settlements which are nearly always marshy during the rains. Some of the flood plains are bad to the extent that they are uninhabited and inaccessible. Except perhaps Bahr Aouk and Bahr Salamat, the numerous streams and rivers are seasonal flowing, only intermittently during the rainy season With
the sandy /muddy substratum, very shallow valleys and slugglish flow, these water systems are not favourable enough to support the breeding of S.damnosum vector flies. So far, no available report, whether speculative or empirical has incriminated any of these rivers as breeding sites of the disease vectors in Chad.
The study villages are rural with very sparse population. Sometimes these settlements of about 150-
400 inhabitants can be up to 70 - 120 km apart. Mllagers are primarily subsistent farmers and with Savanna/Sahelian grassy vegetation, inhabitants are also involved in extensive large-scale livestock production. As a result, the population is normadic. During the long dry season months, grazing of these animals becomes difficult as these villagers (young and old) make long migratory movement in search of food and water; sometimes this takes them into neighboring prefectures or countries.
For successful implementation ofthis exercise, a 3-day REMO training was organized for the Chadian NOTF team which ended with a practicum. Following the REMO documents (WHO, 1992;1995; NGOUMOU & WALSH, 1993) and with appropriate topographical maps (scale of l:200,000 of 1957) and complimentary technical stafl the sample villages (High risk and secondary line villages) were selected taken into consideration uninhabited areas. At the end of the training, two sub-teams (one for prefecture) each were formed and each sub-team was facilitated by a consultant and senior member of the NOTF. In course of the execution of the exercise, village guides/key informants who were familiar with the terrain were involved. The REMO results were appropriately validated in accordance with WHO (1995) protocol and finally analysed using Atlas Geographical Information (Atlas System GIS) This exercise was carried out between February 17 andMarch 2g, 199g. 5
RESULTS
To ensure adequate coverage, a total of 158 villages were selected for this exercise. Out of this
number as many as35 (22 l5%) were inaccessible while another 36 (22.78%) of the selected villages were no longer existing at the time of this study. This gave a total of 7l (4494yo) of fhe
selected villages that were not examined because of obvious factors beyond the control of the team.
Only 87 (55.06%) of the selected villages were examined (Table 1).
The results showed that human Onchocerciasis was absent in 84 (96 55%) of the villages examined
while sporadic cases of Onchocercal nodules were only recorded in 4 (4 60%)villages. three from
Salamat and one from Guera Districts. AII together 6 persons were found to be carrying nodules in the 4 villages' 4 persons from Salamat district (l from Kombol, 2 person from Batimere Rounga of Haraze/Manguagne District and I person from Labado village in Abuo Deia District). The other 2 cases were from Saraf Attai in Mongo District of Guera prefecture.
DISCUSSION
The high number of inaccessibility of selected villages (22.15%) in this study was not unconnected with suspected insecurity associated with the nearly 30 years of civil war in Chad. Vllage heads and guides sometimes adviced non-entry into some of the areas because of suspected active abandoned land mines in the selected communities. Some of the villages had foot track for only the inhabitants and their livestocks. And these were not motorable as they were deliberately allowed by the villagers to be overgrown by bush and shrubs; sometimes block by stumps. According to our key informants, this was done to make people believe that there are no settlements in the areas as well discourage attacking soldiers from entry into the settlement.
A high number of the selected villages (22.78%) were non-existing. Discussions with the key informants showed that this was mainly due the long period of civil war which has continued to cause population movement and re-settlement, sometimes resulting to refugee situation. This, of course, has left hitherto established villages in the maps non-existing. In addition, the inherent mobile nature ofthe normadic villages and the age of the topographical maps (about 41 years) have also contributed to the non-existence of hitherto established settlement. However, this situation did not affect the epidemiological pattern and intensity of Onchocerciasis in the prefectures as the REMO result from the villages examined were good representatives of the disease distribution. 6
The results of the present study shows that human onchocerciasis and endemicity is very low and sporadic in Guera and Salamat Prefectures. As a result, these Prefectures in Chad are not CDTI priority zone. It is believed that these sporadic infections were imported cases as discussion with
infected persons and key informants revealed that these villagers have severally moved into endemic
areas of the Southwestern Prefectures as wellas into Central African Republic (CAR) and Cameroon. Till date no river system in the study area has been incriminated to support the breeding
of S. damnosum vector flies. lnfact, Komboland Batimere Rounga, for example, where three cases
of nodules were recorded are flood plain settlements The nearby Bahr Aouk, bordering CAR is a
slugglish, marshy river with sandy/muddy shallow valley. If indeed there are breeding foci on this
river, and disease transmission has continued, the epidemiological pattern cannot be sporadic as observed in the present study; especially when the villages are high risk (first line).
In the study area, the population is very mobile. This habitual movement constantly take them (old
and young, of all sexes) to the rivers (possible breeding foci) at one time or the other during the year
to feed their livestock. This is one of the major occupational attitudes that has been identified to
expose population to intense disease transmission in endemic zones (NWOKE, 1987, NWOKE et al
1989; 1991). However, the sporadic infection observed in this study does not correspond to the
"expected exposure" of this population. This therefore strongly indicates that these rivers where the present populations are exposed regularly are not breeding sites of vectors or transmission foci of onchocerciasis infection. These scattered onchocerciasis infections observed in this study may not
be different from what Buck and his colleagues (BUCK et al, 1969) described to be cases of "males
whose travel histories or occupational activities in endemic areas suggested that they have acquired their infection outside the villages where they reside permanently.
ACKNOWLEGDEMENT
We remain grateful to APOC for given us the opportunity to serve and contribute and to WR
N'Djamena, WR Lagos, and WR Yaounde for their support. We were in no small measure indebted to NOCP Chad, OPC and Africare for their tremendous encouragement and assistance. We are pleased to especially acknowledge with thanks to Dr Hamdalla of Africare whose constant goodwill, encouragement and hospitality inspired and encouraged us in this challenge. The support of Ministry of Health Chad, Prefec and Sub-prefec, the canton and the District heads as well as the field guide are highly appreciated. Ahmed and Maman, the project drivers were wonderful people in the field. To all that helped in the success of this exercise we say thank you. 7
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