Risk of Malaria Reemergence in Southern France: Testing Scenarios with a Multiagent Simulation Model

Abstract

The Camargue, a region in southern France, is considered a potential site for malaria reemergence. All the suitable factors of the disease transmission system are present -- competent mosquito vectors, habitats for their breeding, and susceptible people -- except for the parasite. The objective of this study was to test potential drivers of malaria reemergence in this system after possible changes in biological attributes of vectors, agricultural practices, land use, tourism activities, and climate. Scenarios of plausible futures were formulated and then simulated using a spatially explicit and dynamic multiagent simulation: the MALCAM model. Scenarios were developed by varying the value of model inputs. Model outputs were compared based on the contact rate between people and potential malaria vectors, and the number of new infections in case of reintroduction of the parasite in the region. Model simulations showed that the risk of malaria reemergence is low in the Camargue. If the disease would reemerge, it would be the result of a combination of unfavorable conditions: introduction of a large population of infectious people or mosquitoes, combined with high levels of people-vector contacts resulting from significant changes in land use, tourism activities, agricultural policies, biological evolution of mosquitoes, and climate changes. The representation in the MALCAM model of interactions and feedbacks between different agents, and between agents and their environment, led in some cases to counterintuitive results. Results from scenario analyses can help local public health authorities in policy formulation.

Pathogenic landscapes: Interactions between land, people, disease vectors, and their animal hosts

“…The model allowed testing potential drivers of malaria re-emergence such as changes in biological attributes of vectors, agricultural practices, land use, tourism activities and climate. Scenarios of possible futures varied the value of exogenous variables (e.g., tourist population visiting the area), initial conditions (e.g., land cover, in response to changes in land use policies or market forces) or parameters (e.g., level of protection of visitors against mosquito bites) [27]. …”

“…Different socio-economic groups are represented in various proportions in different regions of a country. In the Camargue, the scenarios tested using a multi-agent simulation showed that water management practices in rice fields influence the rate of contact between people and potential malaria vectors [27]. According to the flooding date of rice fields, the maximum abundance of vectors and people can be reached simultaneously, resulting in high contact rates.…”

Assessing the future threat from vivax malaria in the United Kingdom using two markedly different modelling approaches

“…Processed-based [50] models and statistical ones [19] have both been used to explore the global risk of malaria, whilst at the local and countrywide scales processed-based models, of differing levels of complexity, have been used for assessing future risk in Europe (France [51,52], Germany [53] and Portugal [54]). The present study differs from these since it uses both processed-based and statistical models to explore the risk of malaria, and validates both models with independent data sets of historical cases of malaria.…”

Analysis of the causes of spawning of large-scale, severe malarial epidemics and their rapid total extinction in western Provence, historically a highly endemic region of France (1745–1850)

“…Data and references concerning past distribution of anophelines in Provence can be found in Ponçon’s thesis [51]. Current data, mainly from Camargue, has been collected by the Didier Fontenille’s laboratory in Montpellier, France [51-56]. …”