Early warning of West Nile virus mosquito vector: climate and land use models successfully explain phenology and abundance of Culex pipiens mosquitoes in north-western Italy

Abstract

BackgroundWest Nile Virus (WNV) is an emerging global health threat. Transmission risk is strongly related to the abundance of mosquito vectors, typically Culex pipiens in Europe. Early-warning predictors of mosquito population dynamics would therefore help guide entomological surveillance and thereby facilitate early warnings of transmission risk.MethodsWe analysed an 11-year time series (2001 to 2011) of Cx. pipiens mosquito captures from the Piedmont region of north-western Italy to determine the principal drivers of mosquito population dynamics. Linear mixed models were implemented to examine the relationship between Cx. pipiens population dynamics and environmental predictors including temperature, precipitation, Normalized Difference Water Index (NDWI) and the proximity of mosquito traps to urban areas and rice fields.ResultsWarm temperatures early in the year were associated with an earlier start to the mosquito season and increased season length, and later in the year, with decreased abundance. Early precipitation delayed the start and shortened the length of the mosquito season, but increased total abundance. Conversely, precipitation later in the year was associated with a longer season. Finally, higher NDWI early in the year was associated with an earlier start to the season and increased season length, but was not associated with abundance. Proximity to rice fields predicted higher total abundance when included in some models, but was not a significant predictor of phenology. Proximity to urban areas was not a significant predictor in any of our models. Predicted variations in start of the season and season length ranged from one to three weeks, across the measured range of variables. Predicted mosquito abundance was highly variable, with numbers in excess of 1000 per trap per year when late season temperatures were low (average 21°C) to only 150 when late season temperatures were high (average 30°C).ConclusionsClimate data collected early in the year, in conjunction with local land use, can be used to provide early warning of both the timing and magnitude of mosquito outbreaks. This potentially allows targeted mosquito control measures to be implemented, with implications for prevention and control of West Nile Virus and other mosquito borne diseases.

Flavivirus Seroepidemiology in Blood Donors in Mersin Province, Turkey

“…Virus x için son konak olan atlar ve insanlar, rezervuar kuşlar ve sivrisinekler arasında gerçekle-şen döngüde enfekte olmakta ancak döngüye katkıda bulunmamaktadır 6 . İnsanlarda WNV enfeksiyonları sıklıkla asemptomatik olmasına rağmen, enfekte kişilerin yaklaşık %20'sinde ateş, döküntü, artralji ve miyalji ile karakterize Batı Nil ateşi; %1'inde ise meningoensefalit, ensefalit ve paralizi gibi bulgular izlenen nöroinvazif enfeksiyon geli- Kene kaynaklı ensefalit (Tick-borne encephalitis, TBE), Japonya ve kuzey Çin'den başlayarak Rusya ve Orta-Kuzey Avrupa'yı içine alan bir bölgede endemik olarak bulunur.…”

Mapping of Aedes albopictus Abundance at a Local Scale in Italy

“…The trap location was included as a random effect to take into account the variability among sampling locations [44]. We carried out multi-model inference to compare all possible models using the R package 'MuMIn' [45], as described in Rosà et al [46]. The models were ranked using AIC, and differences in AIC (∆AIC) between consecutively ranked models were used to calculate the weights and relative evidence ratios for each variable.…”

Evaluation of a Multivariate Syndromic Surveillance System for West Nile Virus

“…Previous early warning systems developed for WNV only identified risk factors of WNV outbreaks, but did not evaluate the detection performances of those systems (Gosselin et al 2005, Shuai et al 2006, El Adlouni et al 2007, Brown 2012, Chaskopoulou et al 2013, Bellini et al 2014bRosà et al 2014, Valiakos et al 2014. Only two attempts to assess the sensitivity and specificity of surveillance have been made (Leblond et al 2007a, Andersson et al 2014, but the parameters of interest were only evaluated based on a limited number of outbreaks, which did not allow any conclusions to be drawn regarding the overall system performance.…”

“…This framework provides a means of weighting the results from syndromic surveillance, and thus, additional information can be easily added. Then, a next step in the early detection of WNV outbreaks should be to test the efficiency of the method with other data, such as the predicted abundance of mosquitoes (Calistri et al 2014, Rosà et al 2014, environmental risk factors (Tran et al 2014), and risk of introduction , Bessell et al 2014). In addition, the Bayesian approach could be easily adapted to spatiotemporal analysis.…”