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THE IMPACT OF CHANGING LANDSCAPES ON TSETSE DISTRIBUTION IN THE ASALS NORTH OF MT. KENYA
IMPACT DES MODIFICATIONS DU PAYSAGE SUR LA REPARTITION DES TSETSE DANS LES TERRES ARIDES ET SEMI-ARIDES (ASALS) DU NORD DU MONT KENYA
G.W. Muriuki1, J. Chemuliti1, R. Changasi1, M. Maichomo1, & J.M. Ndung’u2
1 Kenya Agricultural Research Institute (KARI) – Trypanosomiasis Research Center, P.O. Box 362 Kikuyu, Kenya
2 KARI, Biotechnology Centre, P.O. 14733 Nairobi, Kenya
Résumé
Le Kenya est infesté par huit espèces de tsétsé réparties selon l’utilisation des terres, la végétation et les hôtes. Au niveau local, le programme PATTEC fut d’abord conçu comme une « Approche à grande échelle de la lutte contre les tsétsé au Kenya », et ce, en 2002. Les objectifs de cette phase étaient de fournir des informations exactes et actuelles sur l’ampleur et l’étendue du problème des tsétsé, sur le potentiel d’éradication et l’implication des parties prenantes. Les premiers travaux ont consisté à assurer l’isolement géographique de toutes les zones du pays infestées par les tsétsé sur les cartes numériques de répartition des tsétsé. Des logiciels de système mondial de localisation (GPS) ont été utilisés pour naviguer vers les zones où la présence de tsétsé était signalée. Des échantillons de sang prélevés au bétail ont été testés avec la technique « buffy-coat ». Le piégeage des tsétsé a été effectué avec des pièges biconiques et NG2G ; des évaluations participatives en milieu rural et des évaluations de l’utilisation des terres ont été organisées avec les communautés. Une base de données a été créée pour assurer le suivi des cas dépistés positifs chez le bétail. Des images LandSat (7) de 1999-2001 ont été enregistrées et compléteront les évaluations de l’utilisation des terres et du couvert végétal.
Ces résultats permettent de conclure que la présence des trypanosomes est faible chez le bétail, et que le nombre de zones traditionnellement infestées par les tsétsé a considérablement diminué. Il y a eu d’importants changements dans les modes d’utilisation des terres et, par là même, dans la répartition des tsétsé. De nouvelles zones, abritant auparavant des ranches commerciaux, ont été infestées et converties en réserve de chasse. Le niveau de sensibilisation est plutôt faible chez les communautés vivant dans les nouvelles limites de l’infestation des tsétsé et ce niveau est en chute libre dans les zones traditionnellement infestées par les tsétsé.
Des études longitudinales, l’établissement de protocoles pour la déclaration de statut de zone exempte de tsétsé et l’initiation de programmes de contrôle des tsétsé à l’intérieur des frontières délimitées avant la campagne d’éradication sont autant de recommandations faites par le document. La sensibilisation sur les tsétsé devra être renforcée auprès des communautés qui sont maintenant exposées à la menace.
Summary
Kenya is infested by 8 tsetse species, distributed according to land-use, vegetation and hosts. At a local scale, the PATTEC programme was first conceptualised as “An Area-wide approach to tsetse control in Kenya”, in 2002. The objectives of this phase were to provide accurate and current information on the magnitude and extent of the tsetse problem, eradication feasibility, and involvement of stakeholders. Initial work involved ascertaining the geographic isolation of the tsetse belts that are contained entirely within the country, on the digital maps of tsetse distribution. GPS uploads were used to navigate to the reported incidences of tsetse presence. Livestock blood samples were screened by BCT (Buffy Coat Technique). Tsetse trapping was done with biconical and NG2G traps, PRAs and land use assessments with the communities was done. A database was maintained for follow up of positive cases in livestock. LandSat (7) TM images of 1999 – 2001 were acquired and will complement the field land use/cover assessments.
Findings indicated low trypanosome incidences in livestock and traditional tsetse belts diminished significantly. There have been major changes in land-use and consequently, tsetse distribution. New areas have been infested, where use has reverted to game conservancy from commercial ranching. Awareness is low among the communities in new tsetse frontiers, and derelict in traditional belts.
Longitudinal studies, establishment of protocols for declaration of tsetse free status, and programmes to contain tsetse within the last frontiers prior to the eradication campaign are recommended. Tsetse awareness should be raised among communities now living with the menace.
Introduction
Despite previous and ongoing activities in the majority of trypanosomosis-endemic countries in Africa, the disease, spread by the tsetse fly, remains one of the greatest constraints to livestock production and agricultural intensification in Africa. It is arguably the single most important livestock disease in sub-Saharan Africa (Winrock, 1992). It is also generally accepted that animal trypanosomosis has had a major influence on the history of settlement and land-use in tropical Africa.
The disease trypanosomosis directly constrains the productivity of cattle, sheep, and goats, by reducing birth rates, increasing abortion rates, and increasing mortality rates (Swallow, 2000). In areas where livestock is the main source of traction, trypanosomosis can seriously hamper agricultural expansion. Through these direct impacts on livestock productivity, livestock management, and human settlement, the disease has direct impacts on agricultural intensification. The disease has been shown to have the potential to reduce cattle population by 30-50%, and is one of the factors that constrain the development of specialized dairy enterprises in the subhumid and humid lowlands of the African continent. The presence of tsetse also reduces the attractiveness of frontier areas for new migrants and may reduce the value of agricultural production by 5-10% (Swallow, 2000).
By generally constraining farmers from the overall benefits of livestock, less efficient nutrient cycling, less access to animal traction, lower income from milk and meat, and less access to liquid capital, the disease trypanosomosis reduces both crop yields in mixed farming areas and livestock potential in livestock-producing areas (Kristjanson et al, 1999). It follows therefore from the above argument that the control or removal of the trypanosomosis constraint has the potential of influencing agricultural intensification and therefore land use.
More effective tsetse control in Africa may therefore reduce the constraints imposed by the livestock disease, which lowers productivity, and in some areas, may limit the ability of farmers to keep livestock and plough the land using animal traction.
The challenge of declaring Africa tsetse free remains one of the greatest concerns to member states of the African Union (AU). As highlighted in various working documents on tsetse and trypanosomosis control, it has been established that the tsetse fly infests 37 sub-Saharan African countries. 32 of them are among the 42 most Heavily Indebted Poor Countries (HIPCs) in the world falling under the HIPC initiative of the World Bank (WB).
A major milestone in the history of tsetse and trypanosomosis control was the launch of a campaign at the end of the 26th International Scientific Council for Trypanosomosis Research and Control (ISCTRC) meeting held 1-5 October 2001 in Ouagadougou, Burkina Faso called the Pan African Tsetse and Trypanosomosis Eradication Campaign (PATTEC). This was a follow up to an AU summit by African heads of state and government in Lome, Togo where the task of tsetse eradication as a development objective was made a collective responsibility of individual African countries with a resolve to eradicate tsetse flies from the African continent. This was further looped with the ‘Mombasa declaration’ during the 50th anniversary Golden Jubilee of the ISCTRC where member states were urged to give highest priority ranking to African trypanosomosis in their development programmes.
Materials and Methods
Study area
The area covered in this report represents what were termed as the Arid ad Semi-Arid lands North of Mount Kenya. They roughly cover an estimated area of 26307 km2, and lie above the equator, in two large traditional tsetse belts. The forst is a distinctly isolated pocket falling entirely within the Marsabit Forest Reserve, an island in the desert of high altitude and rainfall surrounded by arid land ranging between ecological zone 6 to 7 (Pratt and Gwynne, 1977)
The study area being reported in this report represents Belt Number 1 as shown n the tsetse distribution map of Kenya.
In Kenya, initial efforts, under the Kenya trypanosomiasis research Institute, (KETRI, now Trypanosomiasis Research Center, KARI) were made to delineate tsetse belts as shown in the tsetse distribution map (1967, revised 1996). This is because despite land use changes having taken place over time, tsetse were distinctly distributed in what appears like isolated belts.
Entomological surveys
Tsetse trapping using both Biconical and NG2G traps was carried out. The traps were baited with acetone and phenol sachets. Traps were emptied after 48 hours and the flies caught sexed, counted and identified. Site selection was based on vegetation cover, proximity of drainage systems and areas with human/animal activities e.g., watering sites and grazing areas.
Epidemiology of trypanosomosis in livestock
Peripheral blood samples were collected from the ear veins of cattle into heparinised capillary tubes. In camels, blood was obtained from the jugular into vacutainer tubes with EDTA. Localities where livestock were screened are depicted in the attached map. Trypanosomes were detected in the whole blood by dark-ground buffy coat phase contrast technique (Murray et al., 1977). Mean packed cell volume (PCV) from heparinised whole blood samples was measured after haematocrit centrifugation (Schalm et al., 1975). This procedure was also used to distinguish between trypanosome species using their morphological characteristics. The herd structure was determined by characterising the cattle into three age groups namely: calves and adults to determine the herd structure. The timing was such that the team visited the area once in the dry season (March 2003) and once soon after the rains (July 2003) to give allowance for emergence of tsetse if any.
Land use assessments
Identification and delineation of tsetse belts was done in MapInfo GIS from the National data base. Uploads to a Garmin 12XL GPS were done for navigation to reported incidences of tsetse according to the 1967 and 1996 tsetse distribution maps. Collection of background data from government, project and other technical reports; Rapid Rural Appraisals and a piling approach to describe land use changes and acquisition of LandSat Tm Imagery taken between 1999 and 2001 to facilitate more accurate mapping of land use and change.
Results
Entomology
As shown in Table 1 and Map 1, in Laikipia district, new areas were found to be infested by tsetse. This appears to be an extension of the tsetse belt previously assumed to be delineated by the Great Rift Valley. All the tsetse catches were Glossina pallidipes.
Traditionally, and according to the tsetse distribution maps, the area was infested by G.longipennis and scattered incidences of G. pallidipes.
Table 1. Tsetse trapping in Laikipia District, December 2003
Area
|
No.of traps
|
No. of tsetse Trapped
|
Species
|
FTDs
|
Biting flies
|
| Laikipia Ranch |
4 |
71 |
G. pallidipes |
8.875 |
4 stomoxys |
| Luonyek |
3 |
0 |
- |
0 |
10 stomoxys |
| Mugie Ranch |
5 |
1 |
G. pallidipes |
0.1 |
4 stomoxys |
| Total |
12 |
72 |
|
|
18 |
FTD = Flies per Trap per Day
Map 1: Tsetse distribution in Kenya showing "isolation" of tsetse belts
The extension and infestation of new frontiers was explained by the conversion of a commercial ranch to a game conservancy, and thereby, a total collapse of tsetse control activities.
Elsewhere, as shown in Table 2, no tsetse were caught in the traditional prime habitat. The map depicts a thick tsetse belt following the Ewaso River drainage all the way, and traversing the expanse game reserves laden with wildlife reservoirs (Buffalo Springs Game Reserve, Samburu National Game Reserve) and strapped between expanse pastoral grazing areas. The land use change is minimal compared to other areas, although the locals attest to a change in the thickness of the forests.
Table 2. Tsetse trapping Samburu District, December 2003
Area
|
No. of traps
|
No. of tsetse Trapped
|
FTDs
|
Biting flies
|
| Longewan |
2 |
0 |
0 |
2 stomoxys |
| Lodung’okwe |
5 |
0 |
0 |
0 |
| Wamba |
3 |
0 |
0 |
0 |
| River Ewaso Nyiro |
4 |
0 |
0 |
0 |
| Total |
14 |
0 |
|
2 |
Marsabit district
In all surveys carried out in both the dry and wet seasons, and using both Biconical and NG2G traps, no tsetse were caught. Veterinary Department Records also indicated absence of tsetse in the area over the years.
Despite the environment being largely unchanged in the Marsabit Forest Reserve, and the abundance of large wild animals, no tsetse were trapped. Only Stomoxys biting flies were evidenced. In the whole area therefore, it appears that the habitat f tsetse has changed significantly, with new areas being infested, and traditional tsetse belts diminishing.
Epidemiology of trypanosomosis in livestock
These are shown in Table 3.and Table 4.
Table 3 Summary of Point prevalences for trypanosomes and mean PCV in Laikipia, Samburu and Isiolo districts, December 2002
| Division |
Number sampled |
Mean % PCV |
Number positive |
Point prevalence |
| Laikipia |
72 |
31.1 |
3 |
4.2% |
| Samburu |
44 |
31.4 |
1 |
2.3% |
| Isiolo |
40 |
22.7 |
0 |
0% |
| Total |
156 |
30.1 |
4 |
2.6% |
The mean point prevalence for trypanosomes in the three districts was 2.6%. Laikipia district had a point prevalence of 4.2% while Samburu had 2.3%. All animals sampled in Isiolo district were negative for trypanosomes. The mean PCV in the three districts was 30.1% with all the four trypanosome positive animals having a PCV of below 25. Trypanosomes identified were all Trypanosoma vivax.
In July 2003, one hundred and twenty heads of cattle (24.5%) and 67 camels (52.34%) had PCV values below 25%. The mean PCV for cattle and camels was 27.6 and 24.0 respectively. All animals with low PCV were treated with trypanocides. Wet season screening found no positive cases in cattle in Marsabit.
Table 4 : Point prevalence for trypanosomosis in camels and cattle March 2003, Marsabit
| Sampling site |
Animal species |
Number sampled |
No. positive/ |
Point prevalence |
| Bubisa |
Bovine |
99 |
1 (T. congolense) |
0.01% |
| Diribgombo |
Bovine |
70 |
0 |
0 |
|
Cameline |
33 |
0 |
0 |
| Karare |
Bovine |
71 |
0 |
0 |
| Loglogo |
Bovine |
50 |
0 |
0 |
|
Cameline |
50 |
2 (T. evansi) |
0.04 |
| Ngurunit |
Bovine |
100 |
1 (T. theileri) |
0.01 |
|
Cameline |
45 |
0 |
0 |
Land Use
Two types of land use change were identified in the ASALs north of Mount Kenya, and which were seen as influencing the re-distribution of tsetse habitat and livestock trypanosomosis therein.
The first is the conversion of rangeland for pastoral grazing into farming and settlements.
In all the ASALs north of Mount Kenya, the predominant land use has been pastoral livestock production. In the recent past however, a large part of Samburu district has been brought under commercial large scale wheat production where rainfall permits. Also, Human population growth and encroachment on previous grazing areas has destroyed tsetse habitat, which has seen its disappearance. Massive deforestation has taken place in areas adjacent to the towns, such as Maralal.
Both wet and dry season trapping and extensive livestock screening yielded negative results in the areas. This is a confirmation of the impact of land use change on tsetse population maintenance. The implications for tsetse eradication are that land use has the potential to maintain barriers to contain the residual tsetse populations for eventual eradication.
Despite the map of Kenya depicting previous infestation by tsetse, navigation to these areas undergoing change yielded no tsetse. There were also no incidences of the disease in cattle. The single case of T.congolense in cattle in the northern frontier was tarced back to cross border livestock trading across the Kenya Ethiopia border.
Map 2: Shifting tsetse habitation?
Discussion
The findings of this work have indicated the invasion of new areas by tsetse and the shrinking of traditional tsetse belts.
This has implications in tsetse eradication, that a thorough reconnaissance needs to be undertaken before instigation of control in order to accurately map the current extent and magnitude of the problem
The infestation of new areas amidst a farming community with little or no experience with tsetse calls for a sensitization of the people before eradication, and institutionalization of control measures for the people now living with the menace, such as use of trypanocidals to cover the susceptible livestock.
The absence of tsetse in traditional pockets such as Marsabit calls for concerted efforts in laying down a longitudinal study, alongside guidelines which should be set out towards declaration of a tsetse free status.
Studies in other areas of Africa have shown that land use changes have a strong impact on tsetse distribution and maintenance (Muriuki, 2005; 2003;, Njoka, 2003; Bourn, 2001; Reid, 1999). As such, it is also anticipated that the changes taking place in the ASALs have largely influenced tsetse presence, and this would therefore mean that the problem may actually be much smaller than anticipated.
The findings of this work are far from conclusive, and are an indicator of how much more needs to be carried out before an eradication campaign is carried out. Particularly, the study recommends institutionalization of longitudinal studies in areas now reported as tsetse free, involvement of all stakeholders, community sensitization, and the setting up of protocols towards declaration of tsetse free status in some areas. This may involve capacity building of the field workers and communities in tsetse work.
The use of the satellite imagery acquired to accurately map current land use and cover in all the areas will be a major milestone not only in planning but also in determining areas undergoing rapid change, and thereby re-focusing efforts for eradication.
References
Winrock International (1992). Assessment of Animal Agriculture in sub-Saharan Africa. Winrock International, USA.
Swallow, B.M. (2000). Impacts of trypanosomiasis on African Agriculture. PAAT Technical and Scientific Series 2. Food and Agriculture Organization (FAO). pp 52
Kristjanson, P.M., Swallow, B.M., Rowlands, G.J., Kruska, R.L., and deLeeuw, P.N. (1999). Measuring effects of African animal trypanosomiasis, the potential benefits of control, and returns to research. Agricultural Systems 9, 79-98.
Muriuki, G.W., Njoka, T.J., Reid, R.S. (2003). Tsetse, wildlife, and land cover change in Ruma National Park, south western Kenya. Human Ecology 14(4), 229-235.
Njoka, T.J., Muriuki, G.W., Reid, R.S., and Nyariki, D.M. (2003). The use of sociological methods to assess land use change: a case study of Lambwe valley, Kenya. Social Sciences 7(3), 181-185.
Bourn, D., Reid, R., Rogers, D., Snow, R., and Wint, W. (2001). Environmental change and the autonomous control of tsetse and trypanosomosis in Sub-Saharan Africa: case studies from Ethiopia, The Gambia, Kenya, Nigeria and Zimbabwe. Environmental Research Group Oxford Limited. Information Press Limited, Oxford,UK. pp 248.
Reid, R.S. (1999). Impacts of trypanosomosis on land use and the environment in Africa: state of our knowledge and future directions. In: Proceedings of the 24th Meeting of the International Scientific Council for Trypanosomiasis Research and Control, Maputo, Mozambique, 29 September - 3rd October 1997, Organisation of African Unity and International Scientific council for Trypanosomiasis Research and Control. pp 607
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