Department of Chrono-environment, UMR UFC/CNRS 6249 aff. INRA, Université de Franche-Comté, Besançon, France.
PLoS Negl Trop Dis. 2008;2(9):e287. doi: 10.1371/journal.pntd.0000287. Epub 2008 Sep 3.
Alveolar echinococcosis (AE) presents a serious public health challenge within China. Mass screening ultrasound surveys can detect pre-symptomatic AE, but targeting areas identified from hospital records is inefficient regarding AE. Prediction of undetected or emerging hotspots would increase detection rates. Voles and lemmings of the subfamily Arvicolinae are important intermediate hosts in sylvatic transmission systems. Their populations reach high densities in productive grasslands where food and cover are abundant. Habitat availability is thought to affect arvicoline population dynamic patterns and definitive host-intermediate host interactions. Arvicoline habitat correlates with AE prevalence in Western Europe and southern Gansu Province, China.
Xiji County, Ningxia Hui Autonomous Region, borders southern Gansu. The aims of this study were to map AE prevalence across Xiji and test arvicoline habitat as a predictor. Land cover was mapped using remotely sensed (Landsat) imagery. Infection status of 3,205 individuals screened in 2002-2003 was related, using generalised additive mixed models, to covariates: gender; farming; ethnicity; dog ownership; water source; and areal cover of mountain pasture and lowland pasture. A Markov random field modelled additional spatial variation and uncertainty. Mountain pasture and lowland pasture were associated with below and above average AE prevalence, respectively.
Low values of the normalised difference vegetation index indicated sub-optimality of lowland pasture for grassland arvicolines. Unlike other known endemic areas, grassland arvicolines probably did not provide the principal reservoir for Echinococcus multilocularis in Xiji. This result is consistent with recent small mammal surveys reporting low arvicoline densities and high densities of hamsters, pikas and jerboas, all suitable intermediate hosts for E. multilocularis, in reforested lowland pasture. The risk of re-emergence is discussed. We recommend extending monitoring to: southern Haiyuan County, where predicted prevalence was high; southern Xiji County, where prediction uncertainty was high; and monitoring small mammal community dynamics and the infection status of dogs.
在中国，泡型包虫病（AE）对公共健康构成严重挑战。大规模筛查超声调查可以检测到无症状的 AE，但针对医院记录确定的区域进行筛查，对于 AE 来说效率不高。预测未检测到或新出现的热点可以提高检测率。田鼠科的田鼠亚科的田鼠和旅鼠是森林传播系统中重要的中间宿主。它们的种群在食物和庇护所丰富的肥沃草原上达到高密度。栖息地的可获得性被认为会影响田鼠种群的动态模式和终宿主-中间宿主的相互作用。田鼠的栖息地与西欧和中国甘肃南部的 AE 流行率相关。
宁夏回族自治区西吉县与甘肃南部接壤。本研究的目的是绘制西吉县的 AE 流行率图，并测试田鼠栖息地作为预测因子。利用遥感（Landsat）图像绘制土地覆盖图。利用广义加性混合模型，将 2002-2003 年筛查的 3205 个人的感染状况与性别、农业、种族、犬只拥有、水源和山地牧场与低地牧场的面积覆盖等协变量相关联。马尔可夫随机场模型用于模拟其他空间变化和不确定性。山地牧场和低地牧场与 AE 流行率低于和高于平均水平分别相关。
低归一化差异植被指数值表明低地牧场对草原田鼠的适宜性较差。与其他已知的流行地区不同，草原田鼠可能不是西吉县泡型包虫的主要宿主。这一结果与最近的小型哺乳动物调查结果一致，该调查显示，在重新造林的低地牧场上，田鼠密度较低，而仓鼠、鼠兔和跳鼠密度较高，这些都是泡型包虫的合适中间宿主。讨论了再次出现的风险。我们建议将监测范围扩大到：预测流行率较高的海原县南部；预测不确定性较高的西吉县南部；监测小型哺乳动物群落动态和犬只的感染状况。
