AlboRun: the hunt for the tiger mosquito

Mosquitoes transmit many major pathogens worldwide. In Réunion, the tiger mosquito, Aedes albopictus, spreads dengue every summer. To control these outbreaks, the local regional health agency monitors this mosquito species using AlboRun , a spatial modelling tool that maps tiger mosquito population density. It was conceived and developed by CIRAD and is described in a recent publication in PlosOne on a study coordinated by Annelise Tran, a CIRAD researchers specializing in remote sensing and spatial modelling.

In Réunion , the health authorities now use AlboRun entirely independently. The tool gives them access to precise maps predicting mosquito density, enabling them to pinpoint the priority zones for control operations. "The health authorities keep a record of their interventions, and compare the information provided by AlboRun with reported cases of dengue, which enables them to optimize the organization of such operations. If dengue is circulating quietly, with few if any declared cases, AlboRun is their only source of information" , Annelise Tran says.

A model to predict mosquito population levels

"AlboRun can predict the number of mosquitoes over time and space, depending on meteorological and environmental variables. It takes account of daily rainfall and temperature, based on information supplied by a network of weather stations, and of other parameters such as the density of breeding sites**", the researcher adds.

The model combines two modelling approaches. One relies on empirical data on mosquito density, from field trapping operation, while the other draws on a mechanistic approach, based on the insect's life cycle . "The two approaches complement each other", Annelise Tran says. "For instance, the correlations pinpointed by the statistical approach, based on data, serve to steer the choice of processes to be taken into account with the mechanistic approach. In turn, the mechanistic approach even provides satisfactory predictions for zones for which there is no data."

The mosquito population dynamic model was conceived in 2011 by Priscilla Cailly, a CIRAD-INRA PhD student, and was applied to the species Aedes albopictus before being spatialized using the Ocelet*** software.

A tool with offshoots in other regions

AlboRun is easy to use, thanks to a computer app that offers maps of the island. It is also easily adapted to other regions and other mosquito species. In December 2019, two other tools derived from AlboRun were launched: one for Mauritius - AlboMaurice - and the other - Arbocarto - for mainland France and its overseas regions. This is a major step forward for vector-borne disease control.

AlboRun was developed with funding from the Agence de Santé Océan Indien, while the tests to improve the tool were funded by two ERDF projects, INTERREG TROI and REVOLINC (ERC).

Reference

Tran A., Mangeas M., Demarchi M., Roux E., Degenne P., Haramboure M., Le Goff G., Damiens D., Gouagna L-C., Herbreteau V., Dehecq J-S., 2020. “Complementarity of empirical and process-based approaches to modelling mosquito population dynamics with Aedes albopictus as an example—Application to the development of an operational mapping tool of vector populations”, PLoS ONE 15 (1): e0227407

Other references

Tran A., L'Ambert G., Lacour G., Benoît R., Demarchi M., Cros M., Cailly P., Aubry-Kientz M., Balenghien T., Ezanno P. 2013. A Rainfall- and Temperature-Driven Abundance Model for Aedes albopictus Populations. International Journal of Environmental Research and Public Health , 10 (5): p. 1698-1719.

Cailly P., Tran A., Balenghien T., L'Ambert G., Toty C., Ezanno P. 2012. A climate-driven abundance model to assess mosquito control strategies. Ecological Modelling , 227 (1): p. 7-17.

* Marie Demarchi (independent geomatics engineer).

** water reserves, often small recipients, in which female mosquitoes lay their eggs.

***Ocelet is a programming language developed by CIRAD that serves to model spatial dynamics