Purse B V, Caracappa S, Marino A M F, Tatem A J, Rogers D J, Mellor P S, Baylis M, Torina A
Institute for Animal Health, Surrey, United Kingdom.
Vet Ital. 2004 Jul-Sep;40(3):303-10.
Vector (911 light-trap catches from 269 sites) and serological surveillance data were obtained during recent bluetongue (BT) outbreaks in Sicily. The distributions of Culicoides vectors are compared with that of bluetongue virus (BTV) to determine the relative role of different vectors in BTV transmission in Sicily. The 'best' climatic predictors of distribution for each vector species were selected from 40 remotely-sensed variables and altitude at a 1 km spatial resolution using discriminant analysis. These models were used to predict species presence in unsampled pixels across Italy. Although Culicoides imicola, the main European vector, was found in only 12% of sites, there was close correspondence between its spatial distribution and that of the 2000 and 2001 outbreaks. All three candidate vectors C. pulicaris, C. newsteadi and C. obsoletus group were widespread across 2002 outbreak sites but C. newsteadi was significantly less prevalent in outbreak versus non-outbreak sites in Messina and BTV has been isolated from wild-caught adults of both C. pulicaris and C. obsoletus in Italy. The yearly distribution and intensity of outbreaks is attributable to the distribution and abundance of the vectors operating in each year. Outbreaks were few and coastal in 2000 and 2001 due to the low abundance and prevalence of the vector, C. imicola. They were numerous and widespread in 2002, following hand-over of the virus to more prevalent and abundant novel vector species, C. pulicaris and C. obsoletus. Climatic determinants of distribution were species-specific, with those of C. obsoletus group and C. newsteadi predicted by temperature variables, and those of C. pulicaris and C. imicola determined mainly by normalised difference vegetation index (NDVI), a variable correlated with soil moisture, vegetation biomass and productivity. The predicted continuous presence of C. pulicaris along the Appenine mountains, from north to south Italy, suggests BTV transmission may be possible in a large proportion of this region and that seasonal transhumance between C. imicola-free areas should not generally be considered safe. Future distribution models for C. imicola in Sicily should include non-climatic environmental variables that may influence breeding site suitability such as soil type.
在西西里岛近期发生蓝舌病（BT）疫情期间，获取了病媒（来自269个地点的911次灯光诱捕捕获量）和血清学监测数据。将库蠓病媒的分布与蓝舌病病毒（BTV）的分布进行比较，以确定不同病媒在西西里岛BTV传播中的相对作用。使用判别分析从40个遥感变量和1公里空间分辨率的海拔高度中，为每个病媒物种选择分布的“最佳”气候预测因子。这些模型用于预测意大利未采样像素中物种的存在情况。尽管欧洲主要病媒伊氏库蠓仅在12%的地点被发现，但其空间分布与2000年和2001年疫情的分布密切对应。所有三种候选病媒——鬃库蠓、纽氏库蠓和废弃库蠓组在2002年疫情发生地点广泛分布，但在墨西拿，纽氏库蠓在疫情发生地点的流行率明显低于非疫情发生地点，并且在意大利，已从野生捕获的鬃库蠓和废弃库蠓成虫中分离出BTV。疫情的年度分布和强度归因于每年活动的病媒的分布和丰度。2000年和2001年疫情较少且集中在沿海地区，原因是病媒伊氏库蠓的丰度和流行率较低。2002年疫情众多且分布广泛，因为病毒传播到了更普遍且数量更多的新病媒物种——鬃库蠓和废弃库蠓。分布的气候决定因素具有物种特异性，废弃库蠓组和纽氏库蠓的分布由温度变量预测，而鬃库蠓和伊氏库蠓的分布主要由归一化植被指数（NDVI）决定，该变量与土壤湿度、植被生物量和生产力相关。预测表明，鬃库蠓在意大利从北到南的亚平宁山脉沿线持续存在，这意味着该地区很大一部分可能存在BTV传播，并且一般不应认为在无伊氏库蠓地区之间的季节性游牧是安全的。西西里岛伊氏库蠓未来的分布模型应纳入可能影响繁殖地适宜性的非气候环境变量，如土壤类型。
