Remote sensing based identification of environmental risk factors associated with West Nile disease in horses in Camargue, France.

The study utilizes geographic information system and remote sensing technologies to identify landscape features that increase the risk of West Nile virus transmission in horses in Camargue, France.

Methodology

• The researchers utilized the SPOT-4 (Satellite Pour l’Observation de la Terre-4) images of the Camargue area to create a map detailing various landscape categories in areas of the epidemic’s focus.
• The geographic information system was used to determine the proportion of various landscape components near 10 sites of confirmed horse disease cases and 17 control sites.
• A spatio-temporal analysis of the outbreaks was conducted, with a focus on a spatial window of 9 km and a temporal window of 18 days—these measurements suggested the most promising results.

Findings

• This analysis identified two significant clusters, both located within the wet areas of Camargue, near the town “Les Saintes Maries de la Mer”. These clusters had a relative risk of 3.35 with the first cluster having a radius of 4 km, while the second one stretched up to 9 km.
• The researchers then analyzed the relationships between these confirmed cases and proportions of the diverse landscape categories by applying a generalized linear model.
• The best model indicated that rice fields and dry bushes, along with open water and wet “sansouire” (a type of marshland dense in vegetation), were significant landscape features associated with the presence of West Nile virus cases among horses.

Significance of the Study

• The study offers crucial insights into how certain environmental factors, particularly landscape features, can influence the transmission of the West Nile virus.
• This could have valuable implications for public health endeavours, specifically those focusing on preventing or mitigating the spread of this disease among horses.
• By understanding these landscape associations, officials could improve planning and implementation of control measures, such as targeting these high-risk areas for additional surveillance or prioritizing them for mosquito control efforts.