Eisen Rebecca J, Lane Robert S, Fritz Curtis L, Eisen Lars
Department of Environmental Science, Policy and Management, University of California, Berkeley, CA 94720, USA.
Am J Trop Med Hyg. 2006 Oct;75(4):669-76.
Ixodes pacificus, particularly the nymphal life stage, is the primary vector to humans of the Lyme disease agent Borrelia burgdorferi in California. During 2004, we collected I. pacificus nymphs from 78 woodland sites in ecologically diverse Mendocino County, which has a moderately high incidence of Lyme disease. Within this county, nymphal density was elevated in forested areas with a growing degree day range of 2,600-3,000 (10 degrees C base). Using a geographic information systems approach, we identified all areas in California sharing these environmental characteristics and thus projected to pose high acarologic risk of exposure to host-seeking nymphal ticks. Such areas were most commonly detected in the northwestern part of the state and along the Sierra Nevada foothills in the northeast, but the analysis also identified isolated areas with high acarologic risk in southern California. This mirrors the spatial distribution of endemic Lyme disease during 1993-2005; most cases occurred in counties to the northwest (58%) or northeast (26%), whereas fewer cases were reported from southern California (16%). Southern zip-codes from which Lyme disease cases had been reported were commonly located in close proximity to areas with high projected acarologic risk. Overall, Lyme disease incidence in zip code areas containing habitat with high projected acarologic risk was 10-fold higher than in zip code areas lacking such habitat and 27 times higher than for zip code areas without this habitat type within 50 km. A comparison of spatial Lyme disease incidence patterns based on county versus zip code units showed that calculating and displaying disease incidence at the zip code scale is a useful method to detect small, isolated areas with elevated disease risk that otherwise may go undetected.
太平洋硬蜱，尤其是若虫阶段，是加利福尼亚州莱姆病病原体伯氏疏螺旋体的主要传播媒介。2004年期间，我们从生态多样的门多西诺县的78个林地采集了太平洋硬蜱若虫，该县莱姆病发病率中等偏高。在该县内，生长度日范围为2600 - 3000（基准温度10摄氏度）的林区若虫密度升高。利用地理信息系统方法，我们确定了加利福尼亚州所有具有这些环境特征的区域，因此预计这些区域存在宿主寻找若虫蜱暴露的高螨学风险。此类区域最常见于该州西北部以及东北部内华达山脉山麓，但分析还确定了南加利福尼亚州存在高螨学风险的孤立区域。这反映了1993 - 2005年期间地方性莱姆病的空间分布；大多数病例发生在西北部（58%）或东北部（26%）的县，而南加利福尼亚州报告的病例较少（16%）。报告过莱姆病病例的南部邮政编码区域通常紧邻预计螨学风险高的区域。总体而言，包含预计螨学风险高的栖息地的邮政编码区域的莱姆病发病率比缺乏此类栖息地的邮政编码区域高10倍，比50公里内没有这种栖息地类型的邮政编码区域高27倍。基于县与邮政编码单位的莱姆病发病率空间模式比较表明，在邮政编码尺度上计算和显示疾病发病率是检测否则可能未被发现的疾病风险升高的小而孤立区域的有用方法。
