Loss Scott R, Hamer Gabriel L, Walker Edward D, Ruiz Marilyn O, Goldberg Tony L, Kitron Uriel D, Brawn Jeffrey D
Department of Natural Resources and Environmental Sciences, University of Illinois, Shelford Vivarium, 606 E. Healey St., Champaign, IL 61820, USA.
Oecologia. 2009 Mar;159(2):415-24. doi: 10.1007/s00442-008-1224-6. Epub 2008 Nov 26.
Vertebrate host diversity has been postulated to mediate prevalence of zoonotic, vector-borne diseases, such that as diversity increases, transmission dampens. This "dilution effect" is thought to be caused by distribution of infective bites to incompetent reservoir hosts. We quantified avian species richness, avian seroprevalence for antibodies to West Nile virus (WNV), and infection of WNV in Culex mosquitoes, in the Chicago metropolitan area, Illinois, USA, a region of historically high WNV activity. Results indicated high overall avian seroprevalence and variation in seroprevalence across host species; however, there was no negative correlation between avian richness and Culex infection rate or between richness and infection status in individual birds. Bird species with high seroprevalence, especially northern cardinals and mourning doves, may be important sentinels for WNV in Chicago, since they were common and widespread among all study sites. Overall, our results suggest no net effect of increasing species richness to West Nile virus transmission in Chicago. Other intrinsic and extrinsic factors, such as variation in mosquito host preference, reservoir host competence, temperature, and precipitation, may be more important than host diversity for driving interannual variation in WNV transmission. These results from a fine-scale study call into question the generality of a dilution effect for WNV at coarser spatial scales.
脊椎动物宿主多样性已被假定为可介导人畜共患的媒介传播疾病的流行，即随着多样性增加，传播会受到抑制。这种“稀释效应”被认为是由感染性叮咬分配给无能力的储存宿主所致。我们在美国伊利诺伊州芝加哥大都市区（一个历史上西尼罗河病毒（WNV）活动高发的地区），对鸟类物种丰富度、鸟类针对西尼罗河病毒抗体的血清阳性率以及库蚊中WNV的感染情况进行了量化。结果表明总体鸟类血清阳性率较高，且不同宿主物种的血清阳性率存在差异；然而，鸟类丰富度与库蚊感染率之间，以及丰富度与个体鸟类感染状况之间均无负相关关系。血清阳性率高的鸟类物种，尤其是北方红雀和哀鸽，可能是芝加哥WNV的重要哨兵，因为它们在所有研究地点都很常见且分布广泛。总体而言，我们的结果表明物种丰富度增加对芝加哥西尼罗河病毒传播没有净效应。其他内在和外在因素，如蚊虫宿主偏好的变化、储存宿主能力、温度和降水等，可能比宿主多样性对驱动WNV传播的年际变化更为重要。这项精细尺度研究的结果对在更粗空间尺度上WNV稀释效应的普遍性提出了质疑。
