Optimising rodent control strategies in rural Madagascar to increase agricultural productivity and reduce zoonotic disease risk

Across the developing world, food insecurity is greatest in rural areas, where smallholder farms predominate. Effectively reducing crop losses from agricultural pests requires both an understanding of the biological processes linked to loss levels and consideration of the societal and cultural issues impacting on the adoption of potential resistance strategies.
Rodent pests contribute significantly to food insecurity due to both pre and post-harvest losses. Globally, rats and mice annually eat and spoil cereals that could feed ~280 million people in developing countries alone. They are also important reservoirs for a range of livestock and human diseases. In some countries in Asia and Africa, increased understanding of processes contributing to variation in rodent pest abundance has led to the successful development of Ecologically Based Rodent Management (EBRM). Experience in SE Asia demonstrates that EBRM targeting community actions at key times of year in specific locations can significantly reduce losses, and emphasises the importance of integrating socio-cultural factors through building on local knowledge, experiential learning and social capital (1).
In Madagascar, undernourishment remains a prevalent and persistent problem. Smallholders predominate, with production mainly aimed at domestic subsistence. Rice is the staple food, with both irrigated and pluvial rice cultivation. The black rat, the major rodent pest, is found in all habitats from forest to cultivated areas and villages, and is also a reservoir for zoonoses, including plague. EBRM is not presently practiced in Madagascar and there is an opportunity to develop strategies that improve both food security and human health.
Previous studies in Madagascar provide some evidence of how differences in the seasonality of rat reproduction and peak abundance depend on variation in resource availability at local and landscape scales, as well as evidence of movement between habitats (2). However, as the timing of crop damage is crucial to the ultimate impacts on productivity, with rice able to at least partially compensate for damage incurred at some growth stages (3), it is essential to identify the habitats that act as sources of rats at critical times and the scale at which movements between habitats operate. In addition, to maximise the effectiveness and adoption of EBRM, it is important to understand the scale of the losses incurred by smallholders with different cropping practices (e.g. irrigated vs pluvial rice, inter-cropping) and any societal or cultural factors that may act as barriers to acceptability of control options (e.g. labour shortages at key times, fear of disease).
This interdisciplinary project will consider EBRM strategies for heterogeneous rural landscapes in Madagascar - with the twin objectives of increasing productivity (through reducing pre and post harvest losses), and reducing the risk from rodent-borne disease. This project will (i) use existing rodent trapping data, remotely sensed data on land-use and local knowledge to produce seasonal risk maps for rodent abundance; (ii) use tri-trophic predator-herbivore-plant models borrowed from population ecology to explore the interactions between rice, rats and humans and identify the key points in the seasonal cycle for high-impact control; (iii) build on existing questionnaire data related to perceptions of rodents, to collect detailed information on what impact rats have, what control/resistance strategies are currently employed and how local networks (e.g. farmer co-operatives) may support any action; (iv) use field experiments to examine movement patterns of rats at key points in the rice growing season and quantify pre and post-harvest losses for smallholders with different cropping practices and (v) with continued participation of local stakeholders and communities integrate the findings to consider how to effectively implement control on the ground.