Project

ENIDE

Long-term monitoring of non-intentional effects of larvicides used for mosquito control on aquatic invertebrates in French Atlantic coastal wetlands

Timeframe : 2006 - 2015 Local Budget: 0 € Coordinator: ESE research unit Contact: Laurent LAGADIC Marc ROUCAUTE Keywords : <i>Bacillus thuringiensis israelensis</i>, Larvicide, Mosquito control, Non-target invertebrates, Taxonomic richness and diversity, Bird food resources, Long-term field biomonitoring, Wetlands

Research

Context and Issues

Both the increase in human mobility and climate change contribute to the globalisation of vector-borne diseases. Some mosquito species are efficient disease vectors in Europe, thus increasing the risk of epidemic (re)emergence. In such a context, mosquito control is of primary importance for human and animal health. Bacillus thuringiensis var. israelensis (Bti) is considered the most efficient larvicide to control mosquito populations with negligible environmental impacts. However, repeated field applications of Bti over many years raises the issue of possible long-term effects on non-target invertebrates, with subsequent alterations of food webs. Up to now, environmental effects of Bti have been studied mainly in continental freshwater wetlands. Much less is known about its effects in brackish water coastal wetlands.

Objectives

The objective of the study is to investigate whether repeated treatments of Bti, applied as VectoBac® WG over consecutive years, affects non-target invertebrate communities in wetlands of the French Atlantic coast. Particular attention is devoted to invertebrates potentially used as food resources by shorebirds and wading birds.

Methodology

• Invertebrates have been sampled in the water and sediment of control and VectoBac®-treated wetlands since 2006 in the Morbihan department and since 2010 in the Loire-Atlantique, Vendée, Charente-Maritime and Gironde departments, thus covering the entire area where the Etablissement Interdépartemental de Démoustication du littoral Atlantique is in charge of controlling mosquito populations.
• Non-target invertebrate taxa abundance data are used to calculate community descriptors and to analyse potential structural changes due to VectoBac® using the principal response curve method and similarity analysis.
• Environmental parameters are measured in each invertebrate sampling site, so that homogeneity of the environmental conditions between the control and treated areas can be continuously checked.

Results

• Based on the data obtained in Morbihan between 2006 and 2012, we demonstrated that long-term use of VectoBac® WG in coastal wetlands had no influence on the temporal evolution of the taxonomic structure and taxa abundance of non-target aquatic invertebrate communities, which is highly driven by abiotic factors. In addition, over the long term, the amount of invertebrates that could be used as food resources by birds was maintained in VectoBac®-treated areas.
• Reduced application rate and targeted spraying of VectoBac® WG in mosquito breeding sites obviously minimize potential environmental impacts of Bti. Even so, surveillance of its possible primary side effects is needed, which requires comparable control and treated areas. The deployment of our methodology along French Atlantic coastal wetlands where VectoBac® WG is used to control larval mosquito populations will provide an overall assessment of the potential effects of Bti on non-target aquatic invertebrates over the long-term at a large geographical scale. This study represents the largest investigation ever conducted to analyse non-intentional effects of Bti-based mosquito control in wetlands.

Publications issued from the project

People involved

LAGADIC Laurent, Scientist Phone : +33 2 23 48 52 37 Email : laurent.lagadic@inrae.fr

ROUCAUTE Marc, Technician Phone : +33 2 23 48 70 38 Email : marc.roucaute@inrae.fr

Partners

Funding and Support

District Councils of Charente-Maritime, Gironde, Loire-Atlantique, Morbihan and Vendée (annual budget)