Bull. Soc. Pathol. Exot. DOI 10.1007/s13149-010-0087-3

LETTER TO THE EDITOR / LETTRE À LA RÉDACTION

Tsetse control and in , quo vadis? Lutte contre la mouche tsé-tsé et la trypanosomiase en Afrique : où va-t-on ?

N. Dräger

Revised: 22 December 2009 , Accepted: 5 January 2010 © Société de pathologie exotique et Springer-Verlag France 2010

Abstract National and international efforts to eradicate Introduction -borne and trypanosomiasis are criti- cally evaluated, and possible reasons for their failure in Dr. GFT. Saunders [12], who worked in the 1930s and 40s in many cases are discussed. Some formerly performed cam- West Africa on human sleeping sickness, described the paigns in specific areas with positive results cannot be history of tsetse fly investigations and control with a taken as examples to solve the main problems. In future, a quotation from Mary Kingsley, the intrepid lady traveller, significant reduction of trypanosomiasis cases will be possi- who journeyed through western and equatorial Africa in ble to achieve only if a concerted long-term Pan-African the 19th century: “Coma, interrupted by convulsions”. approach, based on financial security, the continuity of That was 80 years ago. Is it not applicable today? expert staff, and a well-planned, ecologically sound land use, is generally accepted. To cite this journal: Bull. Soc. During the 70s, I was engaged in the field of trypanoso- Pathol. Exot. ■■ (2010). miasis research and tsetse fly control. I investigated the prevalence of T. brucei, T. congolense and T. vivax in Keywords Human sleeping sickness · Investigation · and wildlife in the Ngamiland and Chobe districts of Control · Trypanosomiasis · 1930–1940 · Zanzibar · . I also participated in the first attempts to eradicate Botswana · West Africa tsetse from the Okavango Delta, using fixed wing aircraft spraying ultra low volumes (ULV) of nonpersistent insec- Résumé Les efforts nationaux et internationaux pour ticides, now called sequential aerosol technique (SAT) [2]. éradiquer la trypanosomiase, humaine et animale, propagée After seven years in Botswana, I spent two years in West par la mouche tsé-tsé font l’objet d’une évaluation critique, Africa working as a project manager of a large-scale tsetse et les possibles raisons de leur échec, dans bien des cas, sont fly distribution survey of Northern , but also taking discutées. Certaines campagnes antérieures, ayant donné des part in control projects in , and résultats positifs dans des zones spécifiques, ne peuvent . All this work resulted in scientific papers, servir d’exemples pour résoudre les nombreux problèmes programmes, reports to the government and sets of detailed qui se posent. À l’avenir, on ne pourra obtenir une réduction maps of tsetse fly distribution [3,4,5]. significative des cas de trypanosomiase que si une approche In order to keep up to date with all the various aspects in panafricaine concertée, à long terme, basée sur une solide this field, I subscribed in 1978 to the new Tsetse and assise financière, la continuité des équipes d’experts et un Trypanosomiasis Information Quarterly released by the usage bien planifié et écologiquement viable de la terre, est Centre for Overseas Pest Research in London. The first acceptée par tous. Pour citer cette revue : Bull. Soc. Pathol. volume contained 156 relevant abstracts and listed Exot. ■■ (2010). 31 involved international organisations. The latest 2009 edition, Vol. 32, is now produced by the FAO under the Mots clés Maladie du sommeil (humaine) · Investigation · Programme against African Trypanosomiasis (PAAT). Lutte · Trypanosomiase · 1930–1940 · Zanzibar · Since 1978, the number of abstracts has risen to 14,800, Botswana · Afrique de l’Ouest and of listed organisations to 82! Much of the content is often devoted to reports on meetings and programmes of these organizations, resulting in vast numbers of resolutions, guidelines, proposals and future programmes and projects. N. Dräger (*) Private Bag 1671, ZA-6140 Grahamstown, The application of all this knowledge and technology e-mail : [email protected] has so far resulted only in two successful tsetse fly control 2 Bull. Soc. Pathol. Exot. campaigns leading to permanent eradication in Africa. In To counteract this deteriorating trend, major initiatives Unguja Island, Zanzibar, G. austeni was eradicated by the and programmes were launched in the mid 1990s, aiming sterile technique (SIT) [15] and G. morsitans in at a co-ordinated Pan-African strategy. Initiated by the Orga- Botswana by SAT [10]. The first is an island, and in the nization of African Unity (OAU), supported by FAO and second, the fly distribution is restricted to the Okavango WHO and financed by local governments, foreign aid and Delta, with only the narrow panhandle at the Caprivi the African Development Bank (AfDB), the Programme Strip as possible entry port for reinvasion. Another success- against African Trypanosomiasis (PAAT) and the Pan- ful campaign was carried out in the late 1940s in Zululand African Tsetse and Trypanosomiasis Eradication Campaign [6] using ground and aerial applications of persistent (PATTEC) founded in 2001 have made significant progress insecticide like DDT and BHC. It cleared the fly from in a number of countries. Aiming to eradicate T&T from the South Africa for a long period until re-invasion occurred African continent is an ambitious plan. It requires the from neighbouring territories. And this latter example is full political commitment of individual governments, a typical for the rest of Africa. Over the last 80 years, vast step-by-step strategy, making full use of the resources and stretches of land have been cleared by various methods the latest technology [9]. only to be re-invaded. Fly control measures can now rely on proven methods, A graphic published in a PAAT information pamphlet by like SAT with relatively environmentally friendly insecti- Hursey [8] shows that in 1930, 65,000 deaths from sleeping cides, excellent traps with effective attractants, removal of sickness were recorded; by 1960, the number had dropped to vegetation essential for tsetse survival, pour-on formulation almost none, while in 1998, the number of deaths had again for cattle and SIT. For recording distribution patterns of T&T, increased to about 45,000, according to WHO estimates. GIS and GPS are perfect tools. A number of very effective In West and Central African countries, where chronic curative drugs are available for the treatment of human and sleeping sickness, caused by Trypanosoma gambiense had animal trypanosomiasis. Every aspect of fly biology, ecology been endemic for a long time, the disease was controlled and behaviour has been investigated. The epidemiology, successfully in the 1920s and 1930s by the colonial govern- pathology, immunology and tolerance of human and animal ments by a combination of extensive medical surveys, trypanosomiasis have been studied, and a vast array of chemotherapy and the reduction of the riverine tsetse fly diagnostic tests are now available. Even the genome of habitat. The latter was done very effectively by removing has been described in a paper by dense bush from the riparian vegetation leaving only the 103 (!) authors [1]. Yet, there appears to be a startling larger clean bole trees [12,13]. The eventual drastic reduc- discrepancy between the huge wealth of knowledge accumu- tion of sleeping sickness cases in the late 1950s can also be lated in every sector in this field and the slow progress in the attributed to dedicated, long-serving and highly trained control of disease and vector. senior and junior staff and a long relatively peaceful period. Many programmes and action plans for new control pro- Since independence, strictly organized control programmes jects appear to place too much emphasis to the sterile insect were slowly abandoned, leading to a steady increase of technique. It is doubtless the most ecologically friendly sleeping sickness cases [11]. method of tsetse control, but the rearing of sufficiently large In the last 60 years, many Tsetse and Trypanosomiasis numbers of radiated, sterile males is a sophisticated and very (T&T) projects were started by African governments in expensive process. The method also requires the initial signif- the affected countries and mainly financed by First World icant reduction of the existing fly population by other means agencies. The early pre-insecticide efforts relied on game like SATand an effective barrier against re-invasion of fertile destruction and the far more effective vegetation clearing, males. Vale and Torr [14] have shown that this measure of followed by various types of traps. Eventually, the spraying control is far less cost effective when compared with the use of of fly resting sites with DDT took over until the severe and insecticide-treated cattle (ITC). To reduce the trial populations unacceptable ecological side effects become apparent. by 99%, it took 187 days with ITC and 609 days with SIT, Overseas experts were engaged to supervise tsetse surveys while the costs for the latter are up to 40% greater. and control measures with more environmentally friendly Another prerequisite to insure eradication is the suffi- insecticides, establish laboratories and tsetse fly breeding ciently long-term monitoring of cleared areas, which seems centres and engaged in the training of local specialist staff. to be difficult: it has been shown that, when even very small Eighty-two organizations, mainly from Europe and Africa, numbers of are left alive in a large control campaign, are now involved. Due to tribal wars, civil unrest, lack of eradication cannot be achieved [7], as it happened in the funds or different priorities and subsequent improper land Okavango Delta in Botswana at the first total eradication use policies, most projects were either severely interrupted attempt by SAT in the early 1990s. or had to be completely abandoned and areas cleared of fly Many countries are also lacking the continuity of dedi- were then soon re-invaded. cated, long-serving members of expert senior and junior Bull. Soc. Pathol. Exot. 3 staff. During the colonial period, staff remained in their posts References for many years, as for instance in Ghana, where between 1909 and 1949, only two senior veterinary officers with 1. Berriman M, Ghedin E, Hertz-Fowler C, et al (2005) The genome their staff dealt with animal T&T problems. The reduction of the African trypanosome Trypanosoma brucei. Science 309 of sleeping sickness cases during this period can be (5733):416–22 attributed to medical officers using mobile teams, which 2. Davies JE, Bowles J (1979) Effect of large-scale aerial applica- tions of endosulfan on tsetse fly, Glossina morsitans centralis conducted extensive medical campaigns [12]. All this infor- Machado, in Botswana. Centre for Overseas Pest Research, Mis- mation was captured in meticulous annual reports and maps, cellaneous Report no 45 showing the prevalence of trypanosomiasis and fly distribu- 3. Dräger N, Mehlitz D (1978) Investigations on the prevalence of tion. Unfortunately, such reports were often lost or never trypanosome carriers and the antibody response in wildlife in – utilized by the relevant departments. From my own experi- Northern Botswana. Tropenmed Parasitol 29(2):223 33 ence and that of several colleagues, who worked in similar 4. Dräger N, Kwakwa SO (1980) La mouche tsé-tsé et la trypano- somose au Ghana. Rétrospective et bilan de la situation actuelle. fields, this applies even to our maps and records. This has Actes du Colloque, Korhogo, Côte-d’Ivoire 1979, Eschborn, often led to wasting time and money—duplication of GTZ & Maisons-Alvort, IEMVT. projects. 5. Dräger N (1981) Tsetse fly control in Northern Ghana 1909– Finally, there is the ecological question. Is it really neces- 1980. GTZ Publication, Eschborn 22 pp sary to get rid of tsetse flies countrywide? Shouldn’t certain 6. Du Toit R (1954) Trypanosomiasis in Zululand and the control of tsetse flies by chemical means. Onderstepoort J Vet Res important biomes rather be left without livestock and crops 26(3):317–87 and saved for endemic vegetation and wildlife, including 7. Hargrove JW (2003) Tsetse eradication: sufficiency, necessity tsetse flies? For instance, during my survey of Northern and desirability. Research report, DFID Animal Health Pro- Ghana, the only place where I found any significant numbers gramme, Centre for Tropical Veterinary Medicine, University of of endemic large herbivore species was in the then margin- Edinburgh, UK 8. Hursey BS (2001) PAAT: The Programme against african trypano- ally functional Mole Game Reserve, which also was the last somiasis. Information pamphlet. DFID, Trends Parasitol PO4 strong hold of Glossina morsitans. In the rest of this vast 9. Kabayo JP (2002) Aiming to eliminate tsetse from Africa. Trends area, where only riverine flies (G. tachinoides & palpalis) Parasitol 18(11):473–5 were spotted, wild mammal populations, down to rodents, 10. Kgori PM, Modo S, Torr SJ (2006) The use of aerial spraying to had been reduced to almost nil, in the ever present search eliminate tsetse from the Okavango Delta of Botswana. Acta – – for “bush meat”. Trop 99(2 3):184 99 11. Louis FJ, Ayenengoye C, Ebo’o Eyenga V, et al (2002). Situation Is not the main problem the pressure of an ever increasing de la maladie du sommeil en 2001 dans les états de la zone human population, which will lead to politically favourable, OCEAC. Bulletin de liaison et de documentation de l’OCEAC rather than ecologically sound, decisions? 35(3):8–19 The only way to achieve long-lasting success in the 12. Saunders GFT, Morris KRS (1932) The distribution of human – age-old battle against tsetse fly, nagana and human sleeping trypanosomiasis. West Afr Med J 5(3):39 45 13. Stewart JL (1937) Report on the eradication of tsetse fly of the sickness is good governance, peace and the continuity of G. palpalis Group from the Pong-Tamale area, Northern Territo- expert staff, using the most appropriate scientific methods ries, Gold Coast (Accra: Government Printer). for long-term projects, followed by well-planned land use. 14. Vale GA, Torr SJ (2005) User-friendly models of the cost and Otherwise, the tsetse and Trypanosomiasis problem will efficacy of tsetse control: application to sterilising and insecti- – remain a stop-go affair or “Coma, interrupted by cidal techniques. Med Vet Entomol 19(3):293 305 15. Vreysen MJ, Saleh KM, Ali MY, et al (2000) Glossina austeni convulsions”. (Diptera: Glossinidae) eradicated on the island of Unguja, Zanzibar, using the sterile insect technique. J Econ Entomol Conflit d’intérêt : aucun 93(1):123–35