Spatio-temporal patterns of distribution of West Nile virus vectors in eastern Piedmont Region, Italy

Abstract

BackgroundWest Nile Virus (WNV) transmission in Italy was first reported in 1998 as an equine outbreak near the swamps of Padule di Fucecchio, Tuscany. No other cases were identified during the following decade until 2008, when horse and human outbreaks were reported in Emilia Romagna, North Italy. Since then, WNV outbreaks have occurred annually, spreading from their initial northern foci throughout the country. Following the outbreak in 1998 the Italian public health authority defined a surveillance plan to detect WNV circulation in birds, horses and mosquitoes. By applying spatial statistical analysis (spatial point pattern analysis) and models (Bayesian GLMM models) to a longitudinal dataset on the abundance of the three putative WNV vectors [Ochlerotatus caspius (Pallas 1771), Culex pipiens (Linnaeus 1758) and Culex modestus (Ficalbi 1890)] in eastern Piedmont, we quantified their abundance and distribution in space and time and generated prediction maps outlining the areas with the highest vector productivity and potential for WNV introduction and amplification.ResultsThe highest abundance and significant spatial clusters of Oc. caspius and Cx. modestus were in proximity to rice fields, and for Cx. pipiens, in proximity to highly populated urban areas. The GLMM model showed the importance of weather conditions and environmental factors in predicting mosquito abundance. Distance from the preferential breeding sites and elevation were negatively associated with the number of collected mosquitoes. The Normalized Difference Vegetation Index (NDVI) was positively correlated with mosquito abundance in rice fields (Oc. caspius and Cx. modestus). Based on the best models, we developed prediction maps for the year 2010 outlining the areas where high abundance of vectors could favour the introduction and amplification of WNV.ConclusionsOur findings provide useful information for surveillance activities aiming to identify locations where the potential for WNV introduction and local transmission are highest. Such information can be used by vector control offices to stratify control interventions in areas prone to the invasion of WNV and other mosquito-transmitted pathogens.

Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States

“…LST and NDVI have been used to analyze vector-borne diseases in many previous studies [23], [27], [28]. ETa is a hydrological variable measuring the flux of water from ground to atmosphere via evaporation and transpiration and is thus an indicator of moisture available at near the ground surface.…”

Evidence of mosquito-transmitted flavivirus circulation in Piedmont, north-western Italy

“…A recent investigation on the ecology of mosquito populations in the same study area showed that the environmental features can support the maintenance of competent vectors for mosquito-borne diseases [11]. In this framework it is important to identify and characterize potentially zoonotic agents in the study areas, in order to better clarify the diffusion of mosquito-borne diseases in Northern Italy.…”

West Nile virus diagnosis and vaccination: using unique viral peptide sequences to evoke specific immune responses

“…conclusion WNV is a major (re)emerging human pathogen in the world, (1)(2)(3)(4)(5) requiring the development of new and effective preventive and therapeutic vaccine strategies. Indeed, the recent WNV outbreaks in humans and horses in Europe raise concern on public and animal health, (70,71) and highlight the lack of effective vaccines. In addition, diagnosis of WNV infections is further complicated by extensive antigenic cross-reactivity among flaviviruses.…”