Benefits and costs of a global cooperative surveillance strategy to control trans-boundary crop pathogens

Trans-boundary diseases are extremely complex to control and can cause global socioeconomic damages. In the context of crop protection, surveillance strategies are usually designed according to administrative boundaries. In this study, we investigate to which extent this geographical scale of surveillance is suitable for long-distance dispersed pathogens. We lever on a global epidemic network, presented in a previous work, describing worldwide potential transport of P. graminis, the causal agent of stem rust of wheat. We conceive two surveillance strategies: "Country-based" and "Cooperative" and we compare their performances, in terms of minimizing the number of sentinels deployed, to achieve given surveillance targets, both at the global and country level. As expected, we find that a "Cooperative" strategy is more efficient at the global scale, and this is particularly true for intermediate targets of surveillance. However, costs and benefits of adopting a "Cooperative" strategy are not equally distributed among countries. Medium size countries in central Europe and Asia are those that would benefit most from a cooperative strategy. On the other hand, Greece and Finland, having a small wheat production but placed in important Puccinia pathways, are those that should deploy, in the global interest, more sentinels than they would place in the national interest. Among the major wheat producers, China is the only country that would have a cost from a cooperative strategy, while India, Russia, United States, France and Ukraine would have the most benefits. It follows that the acknowledgement of these discrepancies could help to achieve general stakeholder support for a global international cooperative surveillance system.