Tsetse-fly-transmitted trypanosomiasis remains one of the major disease constraints on improved livestock production in sub-Saharan Africa. It directly reduces productivity in cattle, contributes to mortality, and discourages the use of more productive, improved breeds in infested areas. Particularly affected are pastoral and agropastoral communities, comprising a population of approximately 260 million, among the poorest in Africa.
Current control relies on three principal strategies: trypanocidal drugs, trypanotolerant cattle, and tsetse control or eradication. However, recent research at ICIPE offers a promising alternative technology for tsetse control that would expand the arsenal of techniques available, potentially reducing dependency on trypanocides (thereby conserving this control technique through lower risk of the development of resistance in the causative organism) as well as environmentally hazardous acaracides.
A prototype of the technology has been developed. It is now ready for field testing to adapt it properly to the needs and circumstances of the targeted population of livestock keepers and to formulate appropriate strategies for its use in the integrated control of trypanosomiasis.
The technology is based on a mild, natural repellent of Savannah tsetse species that demonstrated a substantial reduction in the tsetse challenge (>80%) and feeding efficiency on cattle (>90%). The challenge is to evaluate how these repellents can be integrated with other existing techniques to design improved control strategies that rely less on drugs.
Particularly promising is a ‘push-pull’ strategy that uses a combination of repellents (to ‘push’) and baited traps or targets (to ‘pull’) to enhance suppression rates substantially. Integrated control strategies based on repellents will be highly relevant for pastoralist and agropastoralist livestock keepers. The repellent technology will be especially suited for transhumant communities – often among the poorest – since the repellent technology affords full mobility.
In order to assess the biological efficacy of the repellent under field conditions, trials are planned for a pastoral – agropastoral area of Kenya (Nguruman and Narok area).
The twin objectives are to:
- reduce poverty among pastoral and agropastoral communities in sub-Saharan Africa whose livestock are at risk of trypanosomiasis; and
- accelerate the adaptation and transfer to livestock keepers of a new, more cost-effective, biocontrol technique to combat trypanosomiasis, using tsetse repellent refined and field-tested under the programme.
Optimizing the prototype tsetse repellent through laboratory studies
The technology will be refined, including the possibility of augmenting the currently available repellent with other volatile repellents identified from waterbuck (Kobus ellipsiprymnus), and identifying candidate short-range or contact allomones.
Development of an epidemiological model prototype
Related research will be carried out at the International Livestock Research Institute (ILRI) and the Kenya Trypanosomiasis Research Institute (KETRI) on trypanosomiasis infection dynamics, to evaluate the expected impact of repellent-based control. The prototype will be used as input for the appropriate design of field trials, and – as the model is refined based on the results of those trials – it will serve as the basis for a decision-support tool to formulate recommendations for implementing repellent-based control across the various eco-epidemiological situations faced by livestock keepers.
Refining the tsetse repellent technology through researcher-managed field trials
A series of field trials will be designed and implemented to validate critical parameters and results derived from the epidemiological modelling regarding optimal integrated control strategies (i.e. the appropriate proportions of cattle to treat with repellent versus pour-on insecticide in the proposed “push-pull” technique). The performance of the controlled release repellent formulation and devices, their placement and deployment on the animal for long-term use, and their toxicological assessment with respect to animal health will be evaluated.
Socio-economic evaluation of “best-bet” control strategies in farmer-managed trials
“Best-bet” repellent-based control strategies will be identified as a result of the preliminary results from the modelling and researcher-managed field trials. “Best-bet” strategies will be evaluated on farm using a participatory research approach in partnership with livestock keepers and local livestock health services. The economic and technical incentives that will drive eventual uptake of the technology will be assessed. The farmer-based trials will also provide feedback for further adaptive research as needed, to ensure the technology is appropriate for pastoralist production systems.
Development of a business plan for production and delivery
A detailed business plan will be developed to identify and evaluate possible options for commercial production, cofinancing and distribution of repellent products.
Although the project has only just started activities, a successfully adapted and commercially produced repellent product is expected to have significant impact. The current widespread use of trypanocides, which again often represent the single largest livestock health input in pastoralist communities, demonstrates pastoralists’ recognition of trypanosomosis as a critical livestock health constraint, and – more importantly – their willingness to act and invest in protecting their livestock. Assuming that the proposed research confirms the preliminary results suggesting demonstrable reduction in disease incidence when the repellent is used, then uptake should follow as pastoralists realize savings from lower trypanocide use, depending upon the longevity of the eventual commercial repellent product. The technology has the particular advantage that pastoralists can monitor the presence of tsetse on their animals and see for themselves if the repellent works. It is also expected to be attractive for transhumant pastoralist communities for whom alternative tsetse control with traps and targets is often impractical.
It will be important to recognize, though, that successful uptake will also depend on the ability of researchers and livestock health services to formulate appropriate recommendations for using repellent products under varying conditions. These recommendations will be derived from the modelling and field study components of the project. Developing strategies for making this type of information available and accessible to livestock keepers will be addressed through the participation and training of pastoralist communities and livestock health service staff in the study.
Widespread, sustained uptake will be possible only if the technology can be commercially produced and delivered. Current expectations are that repellents would offer a viable commercial product for the private sector, yet affordable to resource-poor livestock keepers. The development of a business plan will be needed to confirm this.
Beyond the direct effects of repellent use, i.e. reducing the incidence of trypanosomiasis, its uptake could also provide potential environmental and human health benefits by reducing the need to use acaricides, including pour-ons. Although the proposed “push-pull” tactic would still entail the use of pour-ons, their use would be much more strategic than is currently the practice, and limited to a small number of target animals.
The expected cost savings and improved cost effectiveness of repellent-based control will enhance its acceptability and uptake, enabling pastoralist communities to improve the productivity of their existing livestock and maintain optimal herd sizes, thereby contributing to higher incomes and improved livelihoods.
