How the FAO and IAEA are assisting the Government of Senegal in its efforts to eradicate tsetse from the Niayes area

How the FAO and IAEA are assisting the Government of Senegal in its efforts to eradicate tsetse from the Niayes area Tsetse transmitted trypanosomosis or nagana is one of the most devastating livestock diseases in Sub-saharan Africa. The disease prevents the integration of livestock keeping with crop production and is therefore considered one of the root causes of hunger and poverty in Africa. The disease is often lethal and leads in addition to a debilitating chronic condition that reduces fertility, weight gain, meat and milk production and work efficiency of oxen used to cultivate the land. Every year, at least 3 million animals succumb to the disease in sub-Saharan Africa.

The Niayes area is located north-east of Dakar, Senegal and has a coastal microclimate favourable to exotic cattle breeds for milk and meat production, but its ecological conditions are also favourable to the tsetse fly Glossina palpalis gambiensis. The G. p. gambiensis population of the Niayes constitutes the most extreme north-western limit of the tsetse distribution in Africa. In 2006, the Government of Senegal embarked on a project with the ultimate aim to create a sustainable G. p. gambiensis free area in the Niayes. The Directorate of Veterinary Services (DSV) of the Ministry of |Livestock of the Government of Senegal is implementing the project in collaboration with the Senegal Institute for Agricultural Research (ISRA) and technical and financial support have been provided by the International Atomic Energy Agency (IAEA) through its Joint FAO/IAEA Programme of Nuclear Techniques in Food and Agriculture and its Department of Technical Cooperation, the USA (through its Peaceful Uses Initiative (PUI)), and France (through the deployment of a CIRAD staff member on site in Senegal).

From 2006 to 2010, a comprehensive feasibility study was undertaken to assess whether a sustainable tsetse free zone could be created in the Niayes and subsequently, to develop and implement the most appropriate control strategy. The study consisted of an entomological base line data collection effort using a stratified sampling strategy (indicating that suitable tsetse habitat was extremely fragmented, that flies were present in very small pockets but at high densities, and that the total infested area was limited to 525 km2), a parasitological and serological survey of the trypanosomosis disease in cattle residing inside and outside the tsetse-infested areas (on average 28.7% of the cattle population was infected), and a population genetics study that indicated the absence of gene flow between the G. p. gambiensis populations of the Niayes and the nearest known population in the west of the main tsetse belt of Senegal and which confirmed the apparent isolated nature of the Niayes population. These data confirmed that the creation of a zone free of G. p. gambiensis in the Niayes would be sustainable without any risk of re-invasion with flies coming from the main tsetse belt in Senegal. The feasibility was completed with a socio-economic survey, carried out on a total of 277 farms,which indicated that farmers located outside the tsetse infested area produced 38% more milk, 64% more meat and sold 2.8 times more livestock than those located in the tsetse infested area for similar herd sizes. An environmental study has been designed to assess any potential impact of the eradication on biodiversity and the ecosystem. Environmental data have been collected throughout the duration of the programme and until now, no significant impact has been measured.

As a result of this study, the Government of Senegal opted for an area-wide integrated pest management (AW-IPM) approach to create a sustainable G. p. gambiensis-free zone in the Niayes. Application of insecticide as pour-on on livestock, impregnated in traps, and in netted fences around pig pens were selected as the most appropriate tactics to reduce the high fly population densities, whereas the release of sterile male flies (the sterile insect technique) would be used as the final eradication component.

How the FAO and IAEA are assisting the Government of Senegal in its efforts to eradicate tsetse from the Niayes area During the period 2008-2011, a number of preparatory activities were carried out that enabled the project to proceed towards the final operational phase: (1) a dispersal center was established in Dakar where pupae are received from a rearing facility in Burkina Faso and adult flies can emerge, (2) a colony originating from the Niayes was established at the FAO/IAEA Insect Pest Control Laboratory (IPCL) in Austria as a back-up should the strain from Burkina Faso not perform adequately in Senegal, (3) mating compatibility was confirmed between the Senegal strain and the Burkina Faso strain in field cage studies at the IPCL, (4) pupae handling and transport protocols were developed at the IPCL and validated during weekly shipments from Burkina Faso to Senegal, (5) ground trial releases were carried out in four different ecosystems to assess the performance of the sterile flies in the target area including competitiveness, survival and dispersal (weekly releases for two years), (6) data on temporal and spatial dynamics of the native fly population were collected over three years including natural abortion rate, (7) a new aerial release machine was developed by the Mexican company Mubarqui to allow chilled adult fly releases, and (8) trial releases were carried with boxed flies from a gyrocopter that proved to be very suited for releasing flies over the target area.

How the FAO and IAEA are assisting the Government of Senegal in its efforts to eradicate tsetse from the Niayes area Operational activities (2011 – present) – The entire project area was divided into 3 operational blocks (Figs. 1 and 2). In 2011, suppression activities using insecticide impregnated targets and as pour-on cattle were implemented in Block 1. This was followed in 2012 by operational ground releases of sterile males in selected release sites and in 2013 by aerial releases using boxed flies. Monitoring activities indicated no wild fly catches since April 2012. In Block 2, > 1200 insecticide impregnated traps were deployed at the end of 2012 which was complemented with a treatment of >2900 cattle with pour-on insecticides as an additional method to suppress the fly population (Fig. 1). Monitoring and control activities were optimized based on a distribution model combining Landsat and MODIS data layers, with a very good PCC (Percentage of Consonants Correct) index of 0.8. During the December 2013 monitoring, wild flies were only trapped in 2 of the 72 monitoring traps of Block 2 indicating excellent suppression. Operational aerial releases of sterile males over Block 2 will be initiated in early 2014.