THE CURRENT SITUATION OF TSETSE AND TRYPANOSOMOSIS IN ETHIOPIA

LA SITUATION ACTUELLE DES TSETSE ET DE LA TRYPANOSOME EN ETHIOPIE 

Miressa Keno

Ministry of Agriculture and Rural Development,Veterinary Services Department
P.O. Box: 62347
ADDIS ABABA- Ethiopia

Background

            Ethiopia is a densely populated country with 70 million peoples wirh about 85% of the population, living in rural areas with agriculture as their mainstay of livelihood. In the Ethiopian context agriculture including livestock, is central to rural development. Livestock plays a major role in agriculture. In addition to its shear number and its direct contribution in terms of GDP and foreign export earning, livestock provides virtually all the draught power for the cultivation and transportation of agricultural crops and people in rural Ethiopia.

            Statistical estimates show that 88% of the human population and 70% of livestock exist in the highlands of Ethiopia that constitutes only 36.3% of the country's land area. The lowlands of Ethiopia that constitute about 63.7% of the land area of the country, therefore support only 12% of the human, and 30% of livestock populations. Most of the highland area of Ethiopia is now heavily degraded and unable to provide sufficient food for the people that live on it.

            Agriculture is mainly rain-fed, has low productivity and is vulnerable to natural and man-made calamities. As a result, food security is a widespread problem in Ethiopia in general and in the rural areas in particular, where close to 25.5 million of the 57 million rural inhabitants living in abject poverty. Rural poverty is caused by a number of factors, prime amongst which is the fact that a substantial proportion of the country's fertile agricultural lowland is rendered inaccessible by the threat of tsetse and trypanosomosis (T&T). Tsetse & Trypanosomosis for the most part, dictate where people live and practice agriculture and keep livestock. It also constrains the use of oxen, which are the most important source of traction on the majority of farms. The relatively few people that currently live in the fertile lowlands suffer from low levels of draught power and productivity that is manifested by low level of meat, milk, and other animal products that compromises the socio-economics and nutritional status of the inhabitants.

            The priority in addressing rural poverty and improving food security in Ethiopia must therefore be by promoting agricultural production in the fertile lowlands and reducing the pressure on over-utilized highlands. The Federal Democratic Republic of Ethiopia has already committed itself to this strategy within its Rural Development Policy and Strategy, and its Agricultural Development Lead Industrialization Strategy of its Poverty Reduction Strategy Paper.

Tsetse and Trypanosomosis

            Tsetse & Trypanosomosis has kept farmers and livestock keepers out of areas that have very high potential for agricultural development.  The problem caused by T&T is not only that of disease but also a significant negative impact on natural resource conservation and sustainable utilization. Increasing gap between population growth and food production creates an increasing pressure for utilization of new land and diversification of food resources. Tsetse transmitted animal trypanosomosis is, therefore, one of the most significant and costly diseases in Ethiopia hindering the effort made for food self-sufficiency.   This is especially true when one considers losses due to mortality and morbidity in domestic animals, cost of livestock treatment and the cost of tsetse control, Inaccessibility of sufficient animal draught power and inaccessibility of T&T infested areas for millions of Ethiopians that are forced to make their living on agriculture in the highly degraded highlands of the country.

Fly species and distribution

            The tsetse flies in Ethiopia are confined to the southern and western regions between longitude 33o and 38o E and latitude 5o and 12o N which amounts to about 200,000 km2. Tsetse infested areas lie in the lowlands and also in the river valleys of Abay (Blue Nile), Baro, Akobo, Didessa, Ghibe and Omo (Fig. 1). The infested area extends from the southern part of the Rift Valley, around the south-western corner of the country and along the western lowlands and escarpments to the Blue Nile. Restricting a further eastward spread is the cold limit imposed by highlands that rise to the height above which tsetse cannot survive, or the semi-desert condition along the southern border east of the Rift Valley.

            To date five species of Glossina (G. m. submorsitans, G. pallidipes, G. tachinoides, G. f fuscipes and G. longipennis) have been recorded from Ethiopia but only four are widespread and significant economic importance. These are G. m. submorsitans and G. tachinoides, which have a west to east distribution across Africa south of the Sahara desert, and G. pallidipes and G. f. fuscipes which often occur together in East Africa, although the former extends far to the south whereas the latter has essentially central African distribution. Out of the nine regions of Ethiopia five (Amhara, Beneshangul-Gumus, Gambella, Oromiya and SNNPR) are infested with more than one species of tsetse flies.

Figure 1: Tsetse infested river basins in Ethiopia

Trypanosome species and distribution

            Six species of trypanosomes are recorded in Ethiopia and the most important trypanosomes, in terms of economic loss in domestic livestock are the tsetse-transmitted species: T. congolense, T. vivax and T. brucei. The closely related T. brucei subspecies, T. b. rhodesiense causes human sleeping sickness. The other trypanosome species of economic importance are T. evansi of camels and T. equiperdum of horses. The tsetse-transmitted trypanosomes (T. congolense, T. vivax and T. brucei) are restricted to the tsetse-infested river basins of the country while T. vivax has a countrywide distribution as a result of its ability to be transmitted through other biting flies. T. evansi is restricted to camel production areas such as Afar, Somali and part of Oromia regions while Dourine (T. equiperdum) is confine to Arsi-Bale highlands (Fig. 2).

Host range

            Economically the tsetse-transmitted trypanosomosis is the most important disease in cattle, with 14 million heads at risk in Ethiopia. All species of domestic animals are susceptible to infection with one or more species of trypanosomes, but trypanosome infections are economically important in cattle, considering its major role in the agricultural economy of the country. Studies conducted on tsetse-transmitted trypanosomosis showed prevalence of 20 – 30% in cattle, 5 – 7% in small ruminants and 20 – 25% in equines. Among the non-tsetse transmitted trypanosomosis, the prevalence of surra ranged from 10 – 15% in camels, and mechanically transmitted T.  vivax infection in cattle ranged from 6 – 10% on the highlands of Ethiopia. Seroprevalence of dourine in horses of Arsi-Bale highlands ranged from 20 – 28%. Among the domestic animals cattle, camel and horses suffer from the disease with signs of anaemia, loss of weight and productivity.

Figure 2: Distribution of pathogenic trypanosomes in Ethiopia

Major activities

Vector control

            In Ethiopia, vector control techniques have been tried and are still in use in the different tsetse infested areas. In Didessa valley the Technical Co-operation Programme (TCP) from FAO initiated a tsetse control/eradication programme in 1986. A low-cost, non-pollutant, effective and community based odour-baited, insecticide impregnated target/trap technology was selected in an initial area of 30 km2 and later extended to some 800 km2. Other programmes include collaborative work between the Ethiopian government and the International Livestock Research Institute (ILRI) in Ghibe valley with different techniques being tested including target technology and pour-on. Another project just completed with EU funds in Didessa valley as part of the East African Region African Trypanosomosis Control Programme is “Farming in Tsetse Control Areas (FITCA)” as an extension of the previous activities. It covered an area of over 4,500 km2 of the upper Didessa valley for controlling tsetse flies toand rehabilitate mixed farming practices.

            Currently tsetse and trypanosomosis problem has drawn seriously attention to the government and several projects have been prepared and are under implementation. Among these is the Southern Tsetse Eradication Project (STEP). Much is expected from this project for sustainable tsetse and trypanosomosis control/eradication. This project is currently under implementation and run by the Ethiopian Science and Technology Commission. The project is designed as a model with its long-term vision to eradicate the tsetse fly G. pallidipes the only species in the Southern Rift Valley. The area, which is deemed to be cleared from this fly species, is estimated to be 25,000km2. The project, which is underway, plans to suppress the fly population up to the minimum level required, after which the sterilized male flies will be released in the areas to totally eradicate the remaining flies and make the land available for integrated agricultural development. The use of insecticide impregnated target and application of pour-on on cattle in the area has suppressed the tsetse population from 4.1 to 0.9 fly/trap/day. As a result the prevalence of bovine trypanosomosis has dropped from 27 to 6% in a period of two years time.

Tsetse and trypanosomosis diagnosis and survey

            Tsetse and trypanosomosis survey and diagnosis is undertaken mainly by NTTICC, regional veterinary laboratories and research and teaching institutes. The five tsetse infested regions of Ethiopia have now the capability for tsetse and trypanosomosis investigation and control activities. Recent surveys by NTTICC in the affected regional states showed that trypanosomosis prevalence rate is very high in Oromia and Benishangul-Gumuz regional states. Tsetse transmitted animal trypanosomosis is widely distributed in the west and south-western lowlands of the country. The situation of tsetse and trypanosomosis, which was not so significant in the early 1960’s in the country, is currently very alarming and there is a crucial demand to curb the condition where the disease is prevalent and imposes colossal direct and indirect damages to the national economy.

Research on tsetse and trypanosomosis

            The research on tsetse and trypanosomosis in Ethiopia mainly focus on the adaptation of different tsetse control techniques, effective use of trypanoocidal drugs and identification and performance evaluation of trypanotolerant cattle breeds. NTTCC and STEP have given emphasis to vector technology while the National Animal Health Research Centre (NARC) in collaboration with ILRI is working on trypanotolerence. The Faculty of Veterinary Medicine, Addis Ababa University in collaboration with STEP, ILRI and other relevant institutes works on the epidemiology of tsetse and non-tsetse transmitted trypanosomosis with major emphasis on the distribution of tsetse and trypanosomosis and degree of drug resistance.   Research findings on vector control technology have shown the importance of insecticide-impregnated targets and the use of pour-on application in reducing the tsetse challenge and incidence of trypanosomosis. Results on the incidence of drug resistance indicate high degree of resistance to diminazene and isometamidium. In areas where drug resistance is a problem, integrated vector and parasite control has been found to be effective. In areas such as Ghibe and Didessa valley the application of vector control along with chemotherapy has significantly reduced the tsetse challenge as well as the disease consequently livestock and crop productivity have increased.  With regard to the trypanotolerance work encouraging results have been obtained.

Capacity building

            The Farming in Tsetse Controlled Areas (FITCA) project is among the others which was funded by the European Commission through the initiation of the African Union Interafrican Bureau for Animal Resources(AU-IBAR) and operated by the Ministry of Agriculture and Rural Development from the year 2000 to 2004. The project mainly focused on capacity building at national and regional levels in Oromia, Amhara, Benishangul Gumuz and Gambella regional states. These regional states are prioritised as they are heavily affected by the menace of tsetse and the disease they transmit animal trypanosomosis. FITCA capacity building focused on

• Training of professionals, sub professionals and farming communities
• Infrastructure development
• Provision of transportation facilities
• Participatory Rural Appraisal
• Studies on: land use, socioeconomic, forestry management, GIS application, environmental assessment and gender main steaming

STEP

            Southern Rift Valley of Ethiopia Tsetse Eradication Project (STEP) is a ten-year tsetse eradication programme of two five-year phase prepared in line with the agreement between the Ethiopian Government and the International Atomic Energy Agency (IAEA) of the United Nations. The Sterile Insect Technique (SIT) is envisaged to supplement the national effort of tsetse and trypanosomosis management, using area wide eradication approach of the resident fly species (Fig. 3) in the Rift Valley, Glossina pallidipes. The programme has two main components:

1. establishment of sterile insect production plant, which is centrally organised and operated and
2. the actual field operation of the fly eradication process, which is implemented on regional level.

Kality Tsetse Mass rearing and Irradiation Center

            The construction of the centre though delayed is now ready to start its mass rearing activity. Two of the modules are ready to give shelter to the already adapted and propagated Kality colony, which is the fourth generation of Arbaminch strain of G. pallidipes. The mass-rearing centre is designed for a large production of sterile male flies, which is the vital component of the project. Currently the centre has a colony of 50,000 G. pallidipes fliesand an adequate collection of blood meal for its fly population.

 
Fig.3 

            Necessary vehicles, equipment, materials and establishments of the field and laboratory facilities have been acquired to enable the smooth implementation of planned activities

            The capacity building component of the project has two basic elements: manpower development and laboratory establishment. Training in various capacities was given both in the country and abroad. More than 27 staff members of the project have attended foreign training programmes ranging from one to six months. In addition, significant numbers of trainings were offered to individuals of collaborating institutions. Moreover, all of the technical staffs of the project have got local trainings on map reading, use of GPS, vegetation classification and sampling, field note taking, tsetse morphology, reproduction and dissection techniques, identification and development of standard criteria for selection and trap deployment, computer training and data entry, parasitological sampling, blood meal analysis, etc.

            As part of the capacity building component, laboratory establishment for some national institutions was done. Some of the institutions (Department of Geology and Geophysics, Addis Ababa University and National Animal Health Research Centre, NAHRC) have acquired high level of competence in their field of specialization.

Faculty of Veterinary Medicine, Addis Ababa University

Tsetse and trypanosomosis is one of the research and training agenda for the Faculty of Veterinary Medicine. Through it’s undergraduate and postgraduate programmes fly survey and disease prevalence studies are being addressed. In collaboration with national and international institutes the Faculty has undertaken several studies on tsetse flies, parasite, disease, drug resistance etc For instance the Faculty in collaboration with STEP has conducted the MSc studies on:

• Distribution, Density and Infection Rates of Tsetse Flies in Selected Sites of Southern Rift Valley of Ethiopia

• Epidemiology of Bovine Trypanosomosis in Selected Sites of the Southern Rift Valley of Ethiopia,

• Integration of Tsetse Survey Data and Agro-ecological Characteristics from remotely Sensed and Field Observation in Geographic Information System in Southern Rift Valley of Ethiopia

• Control of tsetse and trypanosomosis in the Southern Rift valley (STEP area): evaluation of deltamethrine application

• Similarly, collaborative graduate studies were performed between the Faculty and FITCA on drug resistance and socio-economic impact of tsetse-transmitted trypanosomosis in tsetse controlled and non-controlled areas in Didessa valley.

Future Plans

Expand and sustain the intervention:

            The tsetse control activities, which are currently underway shall be strengthen with a particular emphasis on the settlement areas. The settlement scheme aims at settling half a million chronically food insecure households over the coming years. A survey has indicated that approximately one million hectares is available for settlement in Amhara, Tigray, Oromia and Southern Nation and Nationalities People Regional state. Most of these areas however need to be free from tsetse flies.  Therefore tsetse intervention activities will continue primarily in the new settlement areas .The tsetse eradication activities in the southern Rift valley will continue with release of sterile male flies in areas where suppression of the wild fly has been achieved.

Improve coordination:

            Tsetse and trypanosomosis control activates need to be coordinated by the collective effort of the FDRE, all the affected Regional States and all stakeholders, set against a background of an urgent need to rid Ethiopia of the constraints of T&T in agricultural development and food self-sufficiency.

Strengthen capacity:

            The major objective of the capacity building and baseline data and information collection and analysis effort is to enable the country to have the necessary trained and skilled administrative and technical manpower as well field and laboratory equipment for countrywide T&T intervention, and make data and information available.  This would allow the country to make knowledge-based decisions and apply appropriate technologies for the control and eradication of T&T.

Step up research efforts:

            Applied researches need to be strengthening to insure appropriate planning and implementation of the technical aspects of tsetse and trypanosomosis control programmes in Ethiopia. Some of the areas that need due attention are the followings:

• Persistence of insecticides in live baits in different altitudes and seasons
• Persistence of insecticides on targets in different altitudes and seasons
• Performance of different disposable traps
• Performance of different odors and their longevity under field condition
• Experiment to determine preferable targets
• Experiment to determine appropriate trap/target density for fly population suppression and barrier establishment
• Genetic studies to understand fly population movement and their boundaries
• Experiment on strain adaptation and colony establishment for the remaining four tsetse fly species found in Ethiopia
• Epidemiological study on drug resistant strains of trypanosomes

            In conclusion tsetse and Trypanosomosis have kept farmers and poor livestock keepers out of areas that have very high potential for agricultural development. The problem caused by tsetse and trypanosomosis is not only that of disease but also a significant negative impact on natural resource conservation and sustainable utilization. Increasing gap between population growth and food production creates an increasing pressure for utilization of new land and diversification of food resources. In Ethiopia, the emergence of multiple drug resistance has seriously hampered the control of animal trypanosomosis. The resistance trait is known to be stable for a long time and such stocks can spread to wider areas through animal movement and/or the spread of tsetse populations. Tsetse transmitted animal trypanosomosis is, therefore, one of the most significant and costly diseases in Ethiopia hindering the effort made for food self-sufficiency. It is therefore important to remove the burden of tsetse and trypanosomosis and make the infested areas of Ethiopia accessible for wise and sustainable land resource utilization.