THE USE OF INSECTICIDE TREATED- CATTLE AND INSECTICIDE IMPREGNATED TARGETS FOR THE SUPPRESSION OF TSETSE FLY G. PALLIDIPES POPULATION IN THE SOUTHERN RIFT VALLEY OF ETHIOPIA, STEP AREA.

UTILISATION DES BOVINS TRAITES A L’INSECTICIDE ET DES ECRANS IMPREGNES D’INSECTICIDE POUR ELIMINER LA POPULATION DE TSETSE G. PALLIDIPES DANS LA PARTIE AUSTRALE DE LA VALLE DU RIFT EN ETHIOPIE, DANS  LA ZONE DU PROJET (STEP)

Berisha Kapitano¹, Bergene Bancha¹, Gizaw Weldeyes¹, Kasahun Bekele¹ & Temesgen Alemu²        

¹ Regional Project Coordination Office, STEP, P.O.Box, 1438, Awassa, Ethiopia.
² National Project Coordination Office, STEP, P.O.Box 19917, Addis Ababa, Ethiopia. 

            Dans le cadre des efforts d’éradication des tsétsé grâce à la technique de l’insecte stérile (TIS), une campagne d’élimination des tsétsé a été initiée dans la partie australe de la Vallée du Rift, en Ethiopie, à l’aide de pièges NGU, d’écrans imprégnés d’insecticide et de bovins traités à l’insecticide. Ces deux dernières techniques sont les méthodes appropriées pour l’opération à grande échelle dans la zone du projet STEP, tandis que les pièges NGU ont été jugés fastidieux et nécessitent un apport professionnel et des contrôles fréquents. Au cours des deux à trois dernières années d’activités, plus de 30 000 écrans imprégnés d’insecticide ont été déployés, et environ 1,4 million de bovins ont été traités à l’insecticide pour la campagne.

            Afin  d’évaluer l’impact des techniques sur la population de tsétsé et la prévalence de la maladie, une surveillance entomologique et parasitologique a été effectuée. Les résultats de la surveillance ont révélé que l’élimination des tsétsé a considérablement réduit la densité apparente des mouches d’une moyenne de 4,11 mouches/piège/jour avant la campagne à 0,31 mouche/piège/jour pendant l’intervention, soit une réduction de 92 % de la population glossinaire. De même, la prévalence de la trypanosomose a chuté d’une moyenne de   17 % avant la campagne à 7 % pendant l’intervention, soit un taux de réduction de 60 %, et la valeur moyenne de l’hématocrite a augmenté de 23,2 % avant la campagne à 27,9 % pendant l’intervention, soit une hausse de 20,5 %.

            Un changement important a également été noté au niveau de la production animale et agricole. Ce résultat remarquable a, en fait, été obtenu grâce à la participation active de la communauté et des parties prenantes à tous les niveaux ainsi qu’à l’engagement sans faille de l’État.

Mots-clés : Tsétsé, trypanosomose, élimination, pièges, écrans, bovins, communauté et parties prenantes.

            As part of the effort to eradicate tsetse flies using SIT, tsetse suppression was initiated in the southern rift valley of Ethiopia using NGU traps, insecticide impregnated targets and insecticide treated cattle. The later two techniques are the appropriate methods to be used for the Area-Wide Insect Pest control operation in the STEP area while NGU traps were found cumbersome, required high professional input and frequent revisiting ...etc. During the past 2-3 years of operation, over 30000 insecticide-impregnated targets were deployed and about 1.4 million cattle were treated with insecticide (Deltamethrin pour on or the spray formulation) for the campaign.

            To assess the impact of the techniques on tsetse flies population and disease prevalence, both entomological and parasitological monitoring were carried out. The monitoring results revealed that tsetse suppression had  significantly reduced the fly apparent density from an average of 4.11 F/T/D during the pre-control to 0.31F/T/D during the intervention, a 92% population reduction. Similarly, trypanosome prevalence dropped from an average of 17% during the pre-control to 7% during the intervention  percentage reduction of 60% and the mean PCV value rose from 23.2% during the pre-control to 27.9% during the intervention a percentage increase of 20.5%.

            A significant change was also observed on livestock and crop production. This remarkable change was as a result of active participation of the community at all levels and the stakeholders and high commitment of the government.

Key words:  Tsetse, trypanosomiasis, suppression, traps, targets, cattle, community, and stakeholders.

            Tsetse transmitted trypanosomiasis is a major constraint to livestock and agricultural production in the southern rift valley of Ethiopia in particular and Ethiopia in general. Various efforts have been made by different organizations to alleviate the problem by using trypanocidal drugs and conventional tsetse control techniques in  the last 3 decades. However, although the techniques used have proved to be effective, they could not remove the problem but only give a temporary relief. Having seriously considered the menace of tsetse and trypanosomiasis and its enormous effect on the economy of the nation in general and agricultural development in particular, the Federal Government of Ethiopian (FGE) in collaboration with the International Atomic Energy Agency (IAEA) and the Southern Nations Nationalities and Peoples Regional State (SNNPRS) has established the Southern Tsetse Eradication Project (STEP) (Fig. 1). The primary objective of the project being building the national and regional capacity on the use of SIT and eradicating the tsetse fly (Glossina pallidipes) initially from an area of 25000km2 in the southern rift valley of Ethiopia. Obviously, this will contribute significantly to the national poverty reduction strategy in which the country is working hard on in order to meet the millennium goal.

            Before embarking into the tsetse fly suppression program, due consideration was give to the importance of baseline information that would assist in guiding the next phases of the project activities, for which the entomological, parasitological, socioeconomic and environmental data were collected satisfactorily.  With this information available at hand, tsetse fly suppression was initiated in  block one of the project area with involvement of the community.

             The main objective of the tsetse suppression operation was to reduce tsetse fly density and trypanosome prevalence to a level that would allow the application of sterile insect technique (SIT) for the final eradication of flies from the valley. The operation has integrated the conventional tsetse control techniques.

Pre-suppression activities

Capacity building, sensitization and mobilization

            As one of the immediate objectives of the project, efforts were made to build the capacity of the technical staffs of the project and different organizations that would be directly or indirectly involve in the operation through local and /foreign training. Similarly, it was agreed and strongly justified that community participation held the largest share  of responsibility during the fly suppression and was believed to be the key element during the field operation at all levels. To date,   over 3000 community members with in the project operational area were given awareness creation. 

            Moreover, a regional project steering committee chaired by the president of the Regional State (SNNPRS), and the district and peasant association’s tsetse control committees were established to give the required administrative support and help in overall decision making process of the field operation. Similarly, the beneficiary community  willingly participated in target impregnation, target deployment and maintenance; crush pen construction and application of insecticides to cattle, etc. School clubs were also established to strengthen community awareness creation activities. So the results obtained were due to the strong community participation at all levels.

            No strong linkage have also been established with different institutions (research organizations, Universities, NGOs etc) that would enhance the project activities in general and capacity building in particular.

Fig. 1 STEP area

Baseline data acquisition

            The main objective of baseline data collection was to generate information that would help to make appropriate decision for the activities related to tsetse and trypanosomiasis suppression and the subsequent tsetse fly eradication in the STEP area. The baseline data collected so far consisted of field surveys related to the tsetse flies population distribution and density, trypanosome prevalence, information on the socioeconomic and environmental aspects.

Entomological baseline data collection

            The objective of the entomological baseline data collection was to generate sufficient background information on the diversity, seasonal distribution, abundance and ecology of the tsetse in question (Glossina pallidipes) within the project area.

            A total of 105 UTM grids (a grid is a block of 10kmx10km or 100km2 area) in Block-I were surveyed in four cycles (from September 1998 to October 1999) and each cycle covered 3 months. In each surveyed grid, a total of 8 to 28 NGU traps baited with cow urine and acetone was deployed for three days in different vegetation types and altitude gradient.  The entire trap positions were geo-referenced using a hand held GPS (Garmin 48) for further incorporation of the data in GIS. All the vegetation classes and altitude below 2000m sl were covered during the survey. Each trap was visited after three days of deployment and the information gathered (tsetse and other flies caught) was entered into an entomological survey data sheet.

            Out of the total 105 UTM grids surveyed 63 UTM grids (60%) were found to be infested with tsetse fly species of G. pallidipes and G.f fuscipes. G. pallidipes were trapped from 50 grids (47.6%) and G.f.fuscipes was trapped from 5 grids (4.76%) while the remaining 8 grids (7.6%) had a combination of both species. G. pallidipes was dominant tsetse species caught in the project area. In addition, G. f. fuscipus was found in a confined area northwest of lake Abaya, the Deme basin, which was originally not included in the project area but now forms part of the earmarked 10,500 km2  Block-I intervention area of the project. The highest tsetse fly catch during the survey was obtained from grids along Lake Abaya in the west (grid F8, F7, F9 and G10) with the fly apparent density (AD) ranged from 5.73 flies/trap/day in grid G10 to 68.6 flies/trap/day in grid F8 and the lowest catch was 0.01 fly/trap/day respectively from grids E6, J12 L10, J10 and K6 (most of these grids are in the east of Lake Abaya). The altitudes at which tsetse flies were trapped ranged from 786 to 1850m sl. The highest catch of tsetse flies was between altitudes 1100-1500 m sl. In addition 40% of the flies were trapped from the wooded grassland (WGL) vegetation class and the lowest catch (1.4%) was from grassland (GGL) vegetation class.

Parasitological baseline data collection

            To determine the trypanosome situation in the project area, 61sampling sites were randomly selected and a total of 150 cattle were sampled in each sampling points in two seasons, wet and dry season. As for the trap sites during the entomological survey, sampling sites for the parasitological survey were also geo-referenced using a hand held GPS (Garmin 48). The wet season survey was done from May to July, 1999 and the dry season was done from February to April, 2000 seasons. Trypanosome infection in cattle was detected using the buffy coat darkground-phase contrast technique while anaemia was estimated by Packed Cell Volume (PCV) percentage. Identification of trypansoma species was done on Giemsa stained thin blood smears form positive samples. Serum was harvested from a jugular blood sample collected in plane vacutainer for serological analysis with two different antibody detection ELISA tests at the National Animal Health Centre. A total of 20,000 sera were collected and submitted to the Centre for sero-epidemiology work.

            The highest disease prevalence rate detected was 17% during the wet season (Table 1) and the lowest was 1% (Table 2).The percentage of animals with low PCV values (below 25% was high (30%). Low PCV values are a valuable indication on the presence and degree of anaemia, which is the most important clinical sign of trypanosomiasis. Anemia can also be due to infections with helminths, other parasites, and ticks and /or due to poor nutritional status.  The highest trypanosome infection was due to T. congolense (56%) followed by T. vivax (35%), T.brucei (5%) and some mixed infections (4%).

            At higher altitude sites (above 1900masl) no animals were detected with trypanosomes. The average PCV value of the animals was higher and the number of animals with PCV below 25% was lower. The analysis of the four cycle's entomological survey and two seasons parasitological survey generally showed an overlap and positive correlation between the vector and the parasite distribution in block 1 showing that tsetse flies were the main vectors of the disease in Block I of the project area.

Table 1: Summary of parasitological data during the wet season

Table 2: Summary of parasitological data during the dry season

Socioeconomic baseline data collection

            With the objective of obtaining information on the socioeconomic situation of the project area five transects that covered the entire project area (25,000 km2) were drawn. Of the five transects, two transects pass through Block I and the other three passed through the remaining block (BlockII). About 40% of the peasant associations (PA) and 1.5 % of the households in each PA was included in the sample. The data was collected from a total of 6754 geo-referenced households. Data entry and analysis was accomplished and the draft report  prepared.

Environmental assessment 

            The environmental baseline data collection was conducted and the report presented and the information to be used further for the analysis of the impact of tsetse intervention techniques used and eradication of tsetse and trypanosomiasis on the environment.

Tsetse fly population suppression

            Based on the information gathered during the baseline data acquisition, STEP started tsetse fly population suppression program from 2002 through a collaborative effort of the beneficiary community and governmental and non-governmental organizations involved in the rural development activities. The techniques used for the tsetse suppression were odor-baited NGU traps, insecticide-impregnated targets and insecticide treated cattle.

Uses of odour baited NGU traps

            Tsetse control operation was initiated in about 500km2 area of Block I in April 2002. A total of 1500 odor baited NGU traps (Fig. 2)  were deployed with large community participation. The use of this technique has significantly reduced the tsetse population and gave a temporary relief to the farmers. Farmers developed even more interest and confidence on trap technology  when they observed the tsetse flies caught and collected in the trap’s collecting cage which make them believe that the flies are really killed. However, while the suppression went on there have developed some practical problems associated with using traps.  The traps are deployed far away from the settlement areas (in the bushes) and required high professional and community input and frequent re-visiting for maintenance and odour replenishment.  Thus, only a small area could be covered. The technique only  proved to be effective when regular and proper maintenance was made but is not feasible for area wide operation. Thus, the suppression with traps was discontinued and replaced wholly with targets and insecticide treated cattle. 

Figure 2: NGU trap used for suppression

Use of  insecticide impregnated targets

            Over 30000 blue-black-blue targets of 175cmx50cm size were used for the suppression program. The targets were impregnated with Deltamethrin 20% Sc diluted with water to a concentration of 0.8% and deployed in the tsetse habitat at the density of 4-5 targets/km2. Tsetse suppression with targets proved to be effective but still required maintenance and a close follow up by the beneficiary communities and professionals. The cloth material of the targets was imported and the color of the material was observed to fade with in less than 5 months. The fading requires further investigation.

Use of  insecticide treated cattle

            Tsetse suppression was also conducted using the insecticide treated cattle. About 1421260 animals were sprayed with Deltamethrin 1% (both pour on and spray formulations) over the last 3 years. So far, over 70% of large and old animals of cattle in about 10500km2 of Block I and adjacent areas were sprayed. The technique needed less expertise, was very highly attractive to the community and had a quick knock down effect as compared to other techniques. However, there were areas in the project that were partially inaccessible to the existing techniques that need other techniques such as sequential aerosol technique (SAT) that could easily penetrate and bring a significant reduction of tsetse flies to the level which is acceptable for SIT application.

            Monitoring was used to find out the decline of tsetse flies population, trypanosomiasis prevalence and improvement of socioeconomic and other related parameters. An attempt was made to find out the impact of the suppression program as briefly described below. 

Tsetse flies density

            Five NGU traps baited with acetone and cow urine were deployed in each of the 15 sites identified for tsetse flies monitoring. The traps were removed after 72 hours of deployment and the catches collected, identified and counted. The fly apparent density was determined as the mean catch of tsetse flies per trap per day which significantly reduced from an average mean catch of 4.11 F/T/D during the pre-control to 0.31 F/T/D during the monitoring with 92% percent reduction. 

            Further more, only one species of tsetse fly (G. pallidipes) was encountered  in the rift valley during the monitoring, the same as during pre-control/baseline data collection - confirming that the only potential vector of pathogenic trypanosomes in cattle in the southern rift valley of Ethiopia  G. Pallidipes.

Trypanosomes prevalence

            The same number of sites (or some close to those) identified for tsetse flies monitoring were used for the trypanosome monitoring. A total of 50 animals were sampled from each site and an average of 40 animals was selected per site and their blood sample examined using the buffycoat technique. Packed Cell Volume (PCV) was determined. This  increased from 23.17 % during the pre-control to 27.92% during the monitoring a total percentage increment of 20.5%. 

            The capillary tubes were cut and the buffycoat examined for the presence of trypanosomes using a dark ground-phase contrast technique. The overall disease prevalence rate, compared with the pre-control period, revealed a significant reduction, from an average of 17% during the pre-control to 7% during the intervention and the overall reduction of 60%. Thick and thin blood smears were also prepared from the positive samples for trypanosomes species identification.

            The animals selected for the monitoring were all treated with diminazene aceturate (Berenilâ, Hoechest) at the dose rate of 7mgkg-1 body weight after the initial examination. In addition, the animals found parasitaemic and those with PCV below 25% during the subsequent monitoring were all treated with diminazene aceturate (Berenilâ, Hoechest) at the same dose rate. The results of monitoring are shown in Table 3.

Table 3: Summary of the monitoring results in STEP area

Field operation site              Tsetse density (F/T/D)                     Disease prevalence (%)           

                              Pre-intervention    Post-intervention           Pre-intervention     Post-intervention         

Soddo                           4.1                    0.31                                      27                                 6

Dilla                             2.3                    1.36                                      18                               10

Arba minch                   2.29                  0.4                                        23                                 8 

Benefits of the tsetse suppression (farmers’ observation)

            The beneficiary community in various parts of the operation area were interviewed to get additional information on the improvements achieved as a result of tsetse and trypanosomiasis suppression. The community response showed that the control operation had brought a remarkable change on different socioeconomic parameters. They had witnessed that, after the intervention,  there has been increase in the milk yield (from 0.5litre to 1.5liter), an increase in sale price of adult cattle (from 250birr to1500birr), reduced mortality to trypanosomiasis (from 5-10% to < 3%), reduced abortion (10-20% to < 5%), reduced frequency of treatment (15 days to > 3months), oxen working hours(2 to 8hrs), trypanosomiasis case(ca100/day  reduced by 60%) , animals body condition (weak and emaciated before and now highly improved) (Fig. 3), and related parameters.  The suppression program had also reduced ticks and other biting flies that cause nuisance to animals. In addition, the area was identified for resettlement programs. They also reported that pack animals, particularly donkeys had been introduced to their area after the initiation of tsetse suppression.

Conclusion and recommendations

• The use of odour baited traps for tsetse control had certain problems like the need of frequent re-visiting and maintenance to continue using for the tsetse control program. Because of this the traps were totally removed and replaced with insecticide-impregnated targets and insecticide treated cattle.

• At present, tsetse suppression operation is conducted by integrating insecticide-impregnated targets with insecticide treated cattle; although insecticide treated cattle were preferred by the beneficiary community. Insecticide treated cattle was preferred by the beneficiary community because of its immediate effect on the tsetse population, and too, its effect on the biting insects, ticks and other pests on the body of the animal. As the monitoring result indicated, tsetse and suppression had brought a remarkable drop in the fly density and disease prevalence rate.

Figure 3: Well-fed and healthy animals during the intervention

• The overall tsetse fly density detected during the monitoring revealed that the control program resulted in a significant drop of tsetse fly population from 4.11 flies /trap/day of the pre-control peak to 0.31 flies /trap/day. Moreover, the control operation had also resulted in a marked drop in the trypanosome infection rate from about 17% during the pre-control survey to 7.26% during the monitoring.

• The widely distributed targets in the operation area and the large number of insecticide treated cattle grazing in the area had contributed to the low tsetse fly catch and drop in trypanosomiasis prevalence rate. The high mean PCV value observed during the monitoring revealed a very significant change/ improvement of the anaemic situation, which positively correlated with a very low disease prevalence rate detected during the monitoring. In addition, very impressive qualitative changes/improvements on livestock and agricultural production and productivity were obtained as witnessed by the community where people hardly detect a poor body conditioned animal except the newly purchased/introduced ones.

• The high prevalence rate of trypanosomiasis in the pre-control survey was directly related to the high population of tsetse flies. Because the population of biting flies which is still relatively high as compared to the number of tsetse flies during this monitoring could not even maintain the infection that had been detected during the pre-control survey.

•  The input and the collaborative effort of some Non-Governmental Organizations (NGOs) such as Agri-Service Ethiopia Amaro Integrated Food security Program, Kucha Kalehiwot Integrated Rural Development Program and Ethiopian Rural Self-Help Association (ERSHA), etc had played a prominent role in achieving this result.

• Nevertheless, there is a significant inaccessible pocket area in Block I and adjacent areas which is not reached with the existing techniques. These areas, therefore, require more attention. These areas are  located along the lakes, major rivers, and national parks and forests. The areas are far away from the settlement areas and would require community participation to suppress tsetse. Only few or no targets could be deployed there and the insecticide treated cattle hardly penetrate there for grazing.  The areas are likely to remain a continuous source of infestation for the claimed area and should be attacked with the most effective technique possible like SAT that can mop up the flies and make the area ready for the SIT application.

• The community participation observed so far is encouraging but seems to be inclined on spraying animals with the insecticides. The deployment and maintenance of targets, however, had been given a bit less attention than required. Thus, the targets torn out, lost or disturbed were not sought and properly maintained to good working condition level. So, further community awareness creation activities should be conducted continuously to draw the attention of the community to strongly, fully and effectively participation in both target deployment and insecticide application to cattle

• Monitoring should be done in a well structured manner so as to give a scientific explanation. It had been conducted as an additional workload by the field operation teams. Therefore, separate team, which would take as its major activity to properly design/plan and timely execute the work, must be established within the project at the regional office. This would assist greatly in the analysis of the impact of tsetse suppression.

            Finally, it should be emphasized to and understood by all partners involved in the operation that the result achieved must be maintained until sterile insect technique (SIT) is applied for the final eradication of tsetse flies. Therefore, the operation should be continued with no interruption of necessary input (insecticides, targets and others) which may occur due to lack of budget or policy change (like happened in IAEA).

Future work

• Continue tsetse suppression in Block I
• Conduct tsetse and trypanosomiasis survey in the remaining blocks.
• Establish a well-designed monitoring system
• Conduct species compatibility test in different adjacent valleys
• Raise community awareness on tsetse and trypanosomiasis control techniques and the level of their involvement.
• Establish artificial barrier where necessary.
• Conduct sterile male flies test release in identified areas.

Acknowledgements

            The authors are grateful to IAEA for material and technical support and taking part in capacity building, the federal and regional government authorities for their high level commitment, the local government authorities for their coordination and day to day contribution in organizing the community, community members in all the project sites for their willingness to collaborate and participate in deployment and services of targets and  traps and applying insecticides on animals, the Ethiopian Science and Technology Commission (ESTC) for its high level commitment in transferring the technology for the benefit of the poor and the project staff at various levels.   

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