Optimising invasive species control to reduce zoonotic disease risk and agricultural losses in Madagascar

Invasive alien species (IAS) cost a global minimum of US$46 billion annually, including huge agricultural losses and damage to human health and wellbeing. Tackling the socioeconomic impacts of IAS thus has key significance for addressing global susceptibility to disease and hunger. However, developing effective strategies against established IAS requires significantly improving our current knowledge-base and management toolkit.
In Madagascar, the Asian toad Duttaphrynus melanostictus is spreading following an accidental introduction in the east of the island over a decade ago, with multiple socioeconomic and health consequences. As a toxic species, it poisons higher predators like snakes, eliminating predatory constraints on rodent populations (e.g. the black rat Rattus rattus), that are both agricultural pests and reservoirs for zoonotic diseases including plague and leptospirosis. As a predator, D. melanostictus can reduce beneficial crop-pest predator populations and eliminate farmers' additional income generation (e.g. honey production), reducing food availability, household resources and economic empowerment. This invasive species therefore represents an increasingly significant threat, and this project provides an opportunity to advance our ability to improve food security and human health, making progress towards UN sustainable development goals.
Currently direct and indirect interactions between toad and rodent populations and their consequences for socioeconomic and health outcomes are poorly understood. This interdisciplinary project will work in collaboration with the Madagascar Fauna and Flora Group (a local NGO), government and local stakeholders to address these knowledge gaps at a landscape scale. It will combine existing data on toad and rodent distributions and control methodologies in Madagascar, with the potential for new field data collection and individual-based and epidemiological modelling to optimise approaches across the invasion gradient. Key research aspects include:
a) Developing a targeted model of density-driven interactions between toads, rats and apex predator populations to understand the agricultural and epidemiological consequences across the invaded range
b) Investigating the efficacy of control methodologies and strategic options to slow/halt the invasion front and improve detection and response strategies
c) Testing model predictions against field data
d) Assessing the diet of toads across the invasion gradient to determine variation in socioeconomic impacts