Glass Gregory E, Shields Timothy, Cai Bin, Yates Terry L, Parmenter Robert
The W. Harry Feinstone Department of Molecular Microbiology and Immunology, The Johns Hopkins Bloomberg School of Public Health, 615 North Wolfr Street, Baltimore, Maroland 21205, USA.
Ecol Appl. 2007 Jan;17(1):129-39. doi: 10.1890/1051-0761(2007)017[0129:phrafh]2.0.co;2.
Interannual variation in the number of cases of human disease caused by hantaviruses in North America has been hypothesized to reflect environmental changes that influence rodent reservoir populations. This hypothesis postulates that when cases are rare reservoir populations are geographically restricted in patches of suitable habitat. Identifying these sites, which is needed to test the hypothesis, has proven to be a challenge. Satellite imagery of the U.S. Southwest has shown associations among the likelihood of human hantaviral disease and increases in the rodent populations, as well as increased prevalence of Sin Nombre virus (SNV) in rodent populations. In this study we characterize local areas that had environmental signatures that persisted as predicted highest risk sites for human disease through much of the 1990s. These areas represent a small percentage (0.3%) of the region. Exploratory analyses indicate that these areas were not randomly distributed, but were associated with certain landscape characteristics. Characteristics of elevation, slope, aspect, and land cover were associated with persistent high risk. Using multivariate Poisson regression to control for confounding effects, sites with deciduous- or mixed-forest land cover on moderate to steep slopes (>5 degrees) above 2130 m elevation were associated with increasing numbers of years at highest risk. These are candidate locations for refugia. Sites associated with cleared ground or shrubland were less often associated with high risk compared to reference conditions. The seasonal patterns of vegetation growth in persistently high-risk areas were compared to matched locations using MODIS (moderate resolution imaging spectroradiometer) NDVI (normalized difference vegetation index) during a time of a severe drought in the region from 2002 to 2004. Despite the drought and regardless of land cover, the NDVI in persistently highest risk areas had an early onset, with significantly higher levels of green vegetation that lasted longer than at comparable sites. These observations identify locations that can be monitored for the abundance of P. maniculatus and presence of SNV. If these sites are refugia, we predict they will be occupied by infected deer mice when other monitored sites are unoccupied.
北美洲汉坦病毒引起的人类疾病病例数的年际变化被认为反映了影响啮齿动物宿主种群的环境变化。该假设假定，当病例罕见时，宿主种群在适宜栖息地斑块中受到地理限制。识别这些用于检验该假设的地点已被证明是一项挑战。美国西南部的卫星图像显示了人类汉坦病毒病的可能性与啮齿动物种群增加之间的关联，以及啮齿动物种群中辛诺柏病毒（SNV）患病率的增加。在本研究中，我们描述了在20世纪90年代大部分时间里具有持续作为人类疾病预测最高风险地点的环境特征的局部地区。这些地区占该区域的比例很小（0.3%）。探索性分析表明，这些地区并非随机分布，而是与某些景观特征相关。海拔、坡度、坡向和土地覆盖特征与持续高风险相关。使用多元泊松回归来控制混杂效应，海拔2130米以上中度至陡坡（>5度）上有落叶林或混交林土地覆盖的地点与处于最高风险的年份增加相关。这些是避难所的候选地点。与开阔地或灌木丛相关的地点与高风险的关联比参考条件下更少。在2002年至2004年该地区严重干旱期间，使用中分辨率成像光谱仪（MODIS）归一化植被指数（NDVI）将持续高风险地区的植被生长季节模式与匹配地点进行了比较。尽管干旱且无论土地覆盖如何，持续最高风险地区的NDVI开始较早，绿色植被水平显著更高，持续时间比可比地点更长。这些观察结果确定了可以监测白足鼠数量和SNV存在情况的地点。如果这些地点是避难所，我们预测当其他监测地点未被占据时，它们将被感染的鹿鼠占据。
