7-7 tlp,-n a a RAPID EPIDEMIOLOGICAL MAPPING OF ONCHOCERCTASTS (REMO) rN MALAWI MISSION REPORT (UAY L6 - JUNE 1-5, 1997' FOR WORLD HEALTH ORGANTZATION AFRTCAN PROGRAUME FOR ONCHOCERCIASIS CONTROL (APOC) BY DR. B.E.B. NI{OKE (OVlrCP/cTDl 5O4lAPle7 I O40' STATUS: WHO Temporary Adviser (U197 lOt4329l Professor of Medical/Public Health Parasitology & Entomology School of Biological Sciences Imo State University PMB 2000 Owerri, Nigeria i. ' ., Phoner (234)83-23 05 85 (Home) a Fax: (2341A3-23 18 83 ( it, ') t" rfw JUNE 15, 1997 ,, /.l'^ Fr;r lrr iol nr.;1i :.rr" I .,, ;'1 !r 'y[' ruf II ) SUMMARY Under the sponsorship of the African Programme .for Onchocerciasii Control (APOC), Rapid Epidemiological Mapping of onchocerciasis was conducted in Malawi Uelireen 1,6th May and June l-6th L997. During the course of the exercise-, 4O5 villages were primarily selected to be examined for the prevalence of onchocercal nodules of due to which 48 ( 1f-. 85Ul were not sampled - inaccessibility. Pending the final Atlas GIS analysis of the data, the results showed that: L. O onchocerciasis is apparentty absent from all the 5 Northern Districts of Uafawi: ChitiPa, Karonga, Mzimba, Rurnphi, and NkhatabaY. 2.O In the central Region, onchocerciasis is absent in 7 districts of Kasungu, Nkhotakota, salima, Mchinji, Dowa, Ntchisi and Lilongwe out of the 9 Districts. Ntcheu District has endemic communities on the western border with Mozambique as welI as with the southern border with the Mwanza/Neno area. There is also onchocerciasis at the east-central- part of Dedza district. 3. O The Southern Region is the onchocerciasis zone in Malawi. Onchocerciasis is endemic in Thyolo, south and Eastern Mulanje, Phalombe, Mwanza, Chiradzulu, and western and southern BIantyre. The Mwanza and Thyolo onchocerciasis foci spread into meso endemic foci in northern Chikwawa District. 3 LIST OF CONTENTS Title page ""'l Summary 2 List of contents " " 3 ]-.0 INTRODUCTION ........4 2.O MATERIALS AND METHODS ....6 2.L StudY Area ""'6 2.2 Training of National Teams... " " "9 2.3 Planning and Implementation ' ' 10 3. O RESULTS AND DISCUSSION . ].]- 4.0 REFERENCES... ......].3 5.0 ACKNOWLEDGEMENTS ...15 6.0 ANNEXES ..].6 6.1 Trip Schedule ""'L6 6.2 Population of Mal-awi(1"989).... " "t7 6.3 Map of Matawi showing the Present onchocerciasis areas as determined by REMO..l-8 6.4 Summary of REMO results in Malawi May/June L997 19 4 1.0 INTRODUCTION Human onchocerciasis was first formally reported in Malawi by Gopsil (L939). Later Harvey (L967 ) made another report-. These early studies described cases only i" Thyolo District. The first systematic atternpt to present a nation-wide prevalence- 1t'd geographical ai=t.iUrtion of onchocerciisis in Malawi was carried out by Ben-sira and his colleagues in L972. In this study a totaL of 3482? people from alt over the country were randomly chosen ind skin snipped and most of these came from Th-yo]o district. This \^ras followed up subsequently othei epidemiological studies which include the work by -(1-976), (L986), of Rampen ' 'L991)eudaen (L979), Chirambo et AI gurnham (1-988 , . AI1 these studies showed that endemic onchocerciasis is far from being restricted to the Thyolo District as was previously thought. nntomoroqical studies have also confirmed this, ds vector r-ri"= have been found breeding and biting in other areas outside Thyolo (Berner & carr, 1954; Lewis, L96L; Davies, t985; TambaIa, 1-988; Roberts, r-ee0). Before the last two decades or so, simulium neavei complex was the predominant vector of human or"iro"".ciasis in MaIawi, especially on the Thyolo Highlands, the main onchocerciasis foci in the country ao" MeiIIon , 1-930; Lewis ,Lg6L) - with the rapid population growth and movement of people in the l-960s i"'a L97os i; the country (Coleman, L974), and resultant widespread deforestation as welI as other environmental modifications Simulium damnosum complex displaced the less aggressive S.nearrei complex as the main disease vector. Burnham (1991-) noted that the prevalence of Simulium has increased steadily since the 1950s when Berner & Carr (1954) observed that S.damnosum was hardly noticeable. This increase of S.damnosum was to the extent that in Lg85-87, over 99.92 of the l-00,000 Simulium flies caught biting man in the country were S.damnosum s.7. (Roberts, 1990). From the already known bionomics of s.damnosum.s.7., especially the ffignt range and vectorial capacity as welt as Lfre continued movement of inhabitants in the country, the extent to which onchocerciasis is endemic has rernained undefined. This has created Some fundamental questions and difficulty to health planners i-nvolved in onchocerciasis control to operationally define endemic Districts/areas. The definition of people at risk of infection in Malawi is especially important now that wHo executed African Programme for Onchocerciasis Control (APOC) is determined to control 5 this debilitating disease in Africa to such a level that it will no longei be a public health problem or obstacle to socioecoromi" development in the continent. The APOC main strategy for tnis control effort is Community Oirectea Oistrif-uifion (CDD) of ivermectin to endemic areas. For obvious operational reasons, and successful i*pi"*""iation of the cDD strategy, there is, therefore, need for a nation-wide baseline- epidemiological information gathering based on uiriformTstindard procedure to define areas where cDD should be applied, where it is possible and where the disease is not endemic. This information is not readily avaitable or comprehensive in most endemic African countries including Malawi. In Malawi and elsewhere r^lhere onchocerciasis is endemic, and where mass ivermectin distribution has been adopted, the hitherto acceptable conventional diagnostic procedure f or identifying _communi-ti-es e1igibIe f or treatment is the skin lnip method to determine community Microfilarial Rate tcMRl.- The advantage of this method is that it is a specific diagnostic procedure very useful in small scale survey, in irospitals and laboratories, and very reliable. when efficiency of intervention programmes needs to be assessed. However, skin snip method has a lot of technical and Iogistic Iimitations: it is invasive and time consumi-ng, ?equires expensive equipment/materials and cornmunities show poor cooperation. This method is also likely to increale the risk of infection of HIV, infective hepatitis etc (wHo, L9g2). In Malawi in particular, tne skin snip method is complicated by the ieculiar length and the tough topography of the _Great ifift Valley -system as weII as the scattered settlement pattern. arl these make national-wide coverage aifficuft if not impossible by this method' AII these shortcomings taken into consideration, TDR/WHO has developed and adopted an alternative epidemiological assessment method for rapid mapping of human onchocerciasis in endemic countries in Africa. This current method is Rapid Epidemiological Mapping of onchocerciasis (REMO). REMO exercise is based on the prevalence of palpable onchocercal nodules lonchocercomata) in the community. T-ni= has a very good ierationship with community Microfilariar Rate (Taylor et AI, Lggz; wHo , :-gg7). REMO has been used severally in the field in the last 2-3 years and has proven to be simple and non-invasive, rapid and cheap, appllcable and pratticable over wide range of ecological conditions. rt i= also reliable and sensitive regardless of the severity and duration of infection. ft is non-technical acceptable and tolerable in terms of sociocultural and relilious considerations as weII as absence of risk of 6 complications or infections (Nwoke, 1993;L9941 Nwoke et aI l-9931 Ngoumou & Walsh l-993). With the APOC interest to support endemic African countries including Malawi to control human onchocerciasis, and the absence of a comprehensive national-wide epidemiological data on the disease as werr as the urgent need to determine endemic areas where community Directed Distribution of ivermectin should be implemented and at the same time ensure adequate coverage, the objectives of my mission as WHO Temporary Adviser were: 1 To assist the NOTF of Malawi with the training of REMO survey teams and 2 The planning and i-mplementation of REMO surveys throughout Malawi. 2.0 MATERIALS AND METHODS 2.I STT]DY AREA The study area for this mission was Marawi, a randrocked southeast African country of dramatic highrands and extensive lakes. The Repubric of Marawi with a current estimated population of 1,2 miltion occupies a narrow, curvinq strip of rand along the East African Great Rift Valley stretching about 837km from north to south, it has a width varying from 8km to t-60km. rt is bordered by Tanzania to the north, Mozambique to the east and south, and south west, and Zambia to the west. Its total area of l-18,484 sq.km includes some 24,ZOg sq.km. of inland water areas of Lake Malombe, Chilwa, Cniuta and Lake Ma1awi (Green, l_983). While Malawi's landscape is highly varied, there are four basic physicat regions: viz. the East African or Great Rift Valley, the centrar prains, the highrands and the isolated prateau or mountaineous areas. The Great Rift Valley by far the dominant feature of the country i9 a gigantic trough like depressj-on runnin| throughout the country from north to south and containing Lake Marawi and shire River valrey. The Lakers littorar situated along the western and southern shores and ranging from 8km to 24km in width, covers about 8z of the total rand area and is spotted with swamps and Lagoons. The shire River valrey stretches some 4o0km from the southern end of the Lake Marawi at Mangochi to Nsanje at the Mozambique border and contains Lake Malombe at its northern end. The central region prains rise to an artitude of between 760 and tillo 7 metres (2500 4500ft) and lies beyond the littoral to the west.