November 2001 EAST AFRICAN MEDICAL JOUR 4AL 595 East African Medical Journal Vol. 78 No. I I November 2001 LYMPHATIC FILARUSIS IN KENYA SINCE 1910, AND THE PROSPmS FOR ITS ELLMINATIOI I: A REVIEW C. N. Wamae,BSc, MSPH, PhD, Principal Research Officer, C. Mwandawiro. BSc, MSc, PhD, Senior Reva ch Officer, Centre for Microbiology Research. E. Wambayi. BE4 MSc, PhD, Senior Research Officer, Centre for Biotechnology Research and Developmat. S. Njenga BSc. MSc. Research Officer, Centre for Clinical Research. F. Kiliku, DMLT. HDMLT, Rincipal Medical Laborarory Technologist,Cenm for Microbiology Rd.Kenya Medical Research Institute, P.O. Box 54840. Nairobi. Kenya Request for reprints to: Dr. C. N. Wamae, Centre for Microbiology Research, Kenya Medical Research Ins itute, P. 0. Box 54840. Nairobi, Kenya. LYMPHATIC FILARIASIS IN KENYA SINCE 1910, AND THE PROSPECTS FOR ITS ELIMINATION: A REVIEW C. N. WAMAE, C. MWANDAWIRO, E. WAMBAYI, S. NJENGA and F. KILIKU ABSTRACT Objectives: To provide an overview of lymphatic fhriasi in Kenya from the first time its prevalence was reported to the present day, with suggestio~nsof issues that are yet to be resolved and to present the prospects for its elimination. Ikukz sources: Published and unpublished reports on filarias s studies in Kenya. Sady selection: Field-based epidemidogical studies covering a spects of clinical, parasitology, entomology, social, economic, dingwsi and control of filarii sis. Ikukz extraction: Review of published articles in scientific jcmrnals and communications, retrieval and review of published scientific articles front the Internet and personal communications. Ikukz synthesis: Re-organisation and pooling retrieved publk hed data. Conclusions: Almost one century after the first documented report of lymphatic filariasis in Kenya, no National Control Programme has been instituted. However, important findings that have implications on its control have been made and they! hould be utilised to implement a National Control Programme. On implementation of the I iational Control Programme, research should be focussed on the remaining unresolved is! ues and conducted within the framework of the Programme. The World Health Orgaeation has targeted lymphatic fdariasis for global elimination by the year 2020. Kenya is wl :U positioned to formulate her National Plan for Elimination of Lymphatic Filariasis (NPELF) and join dher endemic countries worldwide, which have already launched their ldans, in the global efforts to eljminate lymphatic filariasis as a public Mthproblem. INTRODUCTION clinical" hidden damage of their lymphatic and renal systems(3). Added to this disease burden, there are the Lymphatic filariasis is a major public health problem serious psycl~osocial consequences, the sexual/social throughout the tropical and sub-tropical areas of Asia, dysfunction cff men with hydroceles or other genital Africa, the Western Pacific and some parts of the abnormalities and of young women with lymphoedemaof Americas(1). Over 120 million people in 73 countries the breasts or l:enitals(4,5). Among Wuchereriubancrofti, worldwide areafflicted with lymphatic filariasis, which is Bmgia malay and B. timori, the three aetiologic agents of a leading cause of disabling morbidity. Approximately lymphatic filariasis, W. bancrofti is the only known cause one-third of people with this infection live in India while of infection in Africa where an estimated 564 million another third live in countries in Africa. Most of the persons are either infected or have chronic disease(6). In remaining one-third of the infected population live in the Africa, incluc ing Kenya, the infection predominates in remaining endemic regions. Over 1.1 billion people (20% rural areas wh, :re access to health care is mostly inadequate. of the world's population) live in areas where they are at It is estimatec that all persons living in endemic areas in risk of infection(2). Thus, lymphatic filariasis has been coastal Ken! a are at risk of infection as they are recognised as an important impediment to socioeconomic continuousl~ exposed to infective mosquitoes development in many parts of Africa, Asia, the western (Mwandawirc ,personal communication). Moreover, some Pacific and certain regions of the Americas due to the of the peoplt living in the Lake Region may also be physical disabilities associated with it. A total of 44 infected (Gitf ure, personal communication). million persons currently suffer from one or more clinical Thought Ere have been some significant successes in manifestations such as lymphoedemaand elephantiasis of the control of the disease, in most endemic countries the the limbs or genitals, hydrocele, chyluria, pneumonitis or burden of lyr lphatic filariasis remains unaffected, or is recurrent infections associated with damaged lymphatics. even on the ir crease. However, the introduction in recent The remainder of the 120 million infected have "pre- years of new drugs and improved diagnostic tools to 596 EAST AFRICAN MEDICAL JOUK NAL November 2001 combat the disease prompted the International Task Force ten mile "cosstal strip", the areas along the Tana and on Disease Eradication to identify lymphatic filariasis as Sabaki Rivers and the Mombasa-Nairobi road, excluding one of the six potentially eradicable diseases(7). In 1997, more inland a.eas (Figure I ). the World Health Assembly passed a resolution on the elimination of lymphatic filariasis as a public health Figure 1 problem through mass chemotherapy of affected individuals and appropriate morbidity management of Map of the Kenp coast showing the towns and villages where DEC mass treutmen was curried out (ufier Wijers und Kuleli, 1984) those presenting with clinical signs. Whilst Kenya is endemic for lymphatic filariasis, the disease remains of low priority in health circles although agood proportion of people living in the Coastal region are condemned to psychosocial, physical and reproductive disabilities due to filarial infection. This paper gives an Slyu -- overview of all the major research and control activities, Pate town on bancroftian filariasis in Kenya, from the time it was Lamu town first documented in 1910 to the present time and also Manda describes some of the on-going projects. Since there are Lamu unresolved issues still to be addressed, prospective studies in the field of lymphatic filariasis have been outlined in the last part of the paper. In recognition of Kenya's position in both lymphatic filariasis research and the focal (regional) L7 INDIAN OCEAN endemicity of the disease, the formulation of the National Plan for Elimination of Lymphatic Filariasis (NPELF) is advocated. DOCUMENTED STUDIES Parasitological and clinical investigations (Tables 1, 2 and 3): The only known type of lymphatic filariasis afflicting humans in Kenya is bancroftian filariasis, which is endemic along the Indian Ocean coastal districts of The rnost ex ensive work was carried out in 1977 Kwale, Kilifi, Malindi, Tana River and Lamu. About three (1 I), which coverc:d the same coastal length but extended million people live in areas where transmission occurs. deeper inland, examining only males over 14 years of age The disease causes severe morbidity, deformity and in the four district; of Kwale, KilifiMalindi, Tana River disability in infected persons. It has been known on Pate and Lamu borderiiig the sea (Figure 2). Prevalence in the (Faza) Island, where pioneering epidemiological work wet, densely pop~latedten-mile wide coastal strip was began, since 1910. Documented epidemiological work(8) generally low; it \/as much higher in the more sparsely was conducted in 1921 in Pate Island and the Tana River populated, drier : nland areas. Microfilaria rates and area, during which 3 17 persons (285 males and 32 females) densities seemed t') increase with age but levelled off at inendemic villages wereexamined. Out ofthese, 97 males around the age oi 50 years. Similarly, hydrocele and and 15 females (35.33%) were microfilaraemic. This was elephantiasis incresed steadily with age. Elephantiasis followed by another survey by members of the Division of was found to be more common in the north than the south, Insect-Borne Diseases in 1946 who found eight out of 34 and occurred without the accompanying abnormalities of persons examined in Siyu to have microfilariae in their the genitals. However, the disease in males of the East blood. A human infection rate of 32 % was recorded from African coast is gen :rally characterised by a lack of severe night blood samples in another study carried out in Pate or acute signs of lyr ~phvessel inflammation compared to Island, Figure l(9). The highest parasite density was other parts of the w~rld(12). foundinsix totwenty-yearage group, with themicrofilarial Differencesin tl~eepidemiologyof lymphaticfilanasis densities being three times higher in males than in females, were observed betvfeen a small compact Moslem town despite the latter living in closer contact with the vector. (Mambrui) and an inland rural area (Jaribuni) where A broader survey conducted in 1962 (10) covered 36 people over one yea1 old were examined(l3). In Mambrui, villages in the entire coastline from Vanga near the microfilaria rates ar d densities were lower in the richer Tanzanian border to Pate Island on the northern coast. people living in beter quality houses and higher in the Microfilaria rates were found to vary from 25% in the poor individuals livi ]gin poor quality and less-lit houses. north to 10 % in the south. Men were more heavily infected In Jaribuni,