# Influence of water on the circulation of the West Nile Virus in horses in Southern France

Sophie Pradier, Alain Sandoz, Gaëtan Lefebvre, Annelise Tran, Sylvie Lecollinet, Agnès Leblond

► To cite this version:

Sophie Pradier, Alain Sandoz, Gaëtan Lefebvre, Annelise Tran, Sylvie Lecollinet, et al.. Influence of water on the circulation of the West Nile Virus in horses in Southern France. Retrovirology, 2010, 7, pp.P186. 10.1186/1742-4690-7-S1-P186. hal-02657913

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POSTER PRESENTATION

Open Access

# Influence of water on the circulation of the West Nile Virus in horses in Southern France

Sophie Pradier¹,²*, Alain Sandoz³, Gaëtan Lefebvre³, Annelise Tran⁴, Sylvie Lecollinet⁵, Agnès Leblond²,⁶

From 16th International Symposium on HIV and Emerging Infectious Diseases
Marseille, France. 24-26 March 2010

## Background

West Nile Virus (WNV) affects humans and horses, potentially causing severe neurological manifestations. Recent outbreaks of West Nile fever in horses were reported in Camargue (2000, 2004), Var (2003) and Pyrénées Orientales (2006). The circulation of this virus is strongly influenced by environmental conditions. This study aimed at explaining the circulation of WNV in

horses by quantifying water bodies around equine stables using Landsat images.

## Methods

A total of 135 stables were selected in three French departments (Hérault, Gard, Bouches-du-Rhône) and 1161 horses were tested by serological analysis between 2007 and 2008.

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<footnote>* Correspondence: spradier@vet-alfort.fr
¹Clinique équine ENVA, Maisons-Alfort, France</footnote>
15 Landsat images (August 2006 to August 2008) were classified into 3 classes: open water, flooded vegetation and other. Surface areas of the first two classes were calculated for buffers of 2 to 5 km around each stable and for each date.

Two multivariate analyses were conducted: GLMs to identify which environmental variables were involved in the viral circulation in stables and GRMs to identify the horse variables linked to WNV circulation after retrieving the effect of the environment.

## Results

The best model distinguishing 46 negative stables (no positive horse considering an error threshold of 0.15) from 61 positive stables (at least 1 positive horse) used 2 km buffers and included mean area of flooded vegetation, total number of horses present in the stable, mean area of open water and X and Y geographic coordinate. The first two variables had a positive effect and the other three a negative effect. The model predicted correctly 73% of positive stables and 71% of negative ones. At the horse level, breed, activity and age were significant. See Figure 1.

## Discussion

These results can be used to target the surveillance of this human and equine disease in Southern France.

### Author details

¹Clinique équine ENVA, Maisons-Alfort, France. ²UR 346 Epidémiologie animale INRA, Saint Genès Champanelle, France. ³Tour du Valat, Arles, France. ⁴CIRAD Agirs, Montpellier, France. ⁵UMR 1161 Virologie INRA AFSSA ENVA, Maisons-Alfort, France. ⁶Clinéquine ENVL, Marcy l'étoile, France.

Published: 11 May 2010

doi:10.1186/1742-4690-7-S1-P186

Cite this article as: Pradier et al.: Influence of water on the circulation of the West Nile Virus in horses in Southern France. Retrovirology 2010 7 (Suppl 1):P186.

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