Page L Kristen, Gehrt Stanley D, Robinson Nathaniel P
Biology Department, Wheaton College, Wheaton, Illinois 60187, USA.
J Wildl Dis. 2008 Jul;44(3):594-9. doi: 10.7589/0090-3558-44.3.594.
The raccoon (Procyon lotor) is the definitive host of Baylisascaris procyonis, a large intestinal roundworm that is zoonotic and can result in fatal or severe central nervous system disease in young children. Prevalence of infection among raccoon populations often is high, and in the midwestern United States, B. procyonis has been reported in 68-82% of raccoons. Raccoon populations have increased in response to changes in human land use, and often reach higher densities in urban and suburban landscapes than rural landscapes. However, shifts in foraging behavior among urban raccoons could impact the transmission of B. procyonis if small vertebrate intermediate hosts are not a significant part of the raccoon diet. The objective of this study was to compare prevalence of B. procyonis infection between urban and rural raccoon populations on a regional scale. Necropsy was done on 204 raccoons collected from September through February during 2000-2005 from seven states across the Midwest (regional sample). Baylisascaris procyonis was found in 54% of examined raccoons. Prevalence differed between land-use types (chi2=11.56, df=1, P=0.0007), and was higher among animals collected from rural locations (65%) than those collected in urban locations (41%). Intensity of infection also differed (F=5.52, df=1, P=0.02), with rural raccoons having greater worm burdens (x=29.63+/-36.42) than urban raccoons (x=13.85+/-18.47). Despite high densities of raccoons in urban landscapes, fewer urban raccoons were infected with B. procyonis, suggesting decreased dependence on intermediate hosts as a food source. This possible explanation was supported by a similar trend in prevalence among subsamples of raccoons collected from three Chicago-area populations (local samples) with differing levels of urbanization, population densities, and foraging behavior that had been intensively monitored during 1995-2002. Decreased transmission of B. procyonis in urban landscapes may be due to decreased predation of intermediate hosts, and contact of juvenile raccoons with B. procyonis eggs may be an important factor in maintaining infections within such populations.
浣熊（Procyon lotor）是浣熊贝蛔虫（Baylisascaris procyonis）的终末宿主，浣熊贝蛔虫是一种大型肠道蛔虫，具有人畜共患性，可导致幼儿出现致命或严重的中枢神经系统疾病。浣熊种群中的感染率通常很高，在美国中西部，已报道68%-82%的浣熊感染了浣熊贝蛔虫。浣熊种群数量因人类土地利用变化而增加，且在城市和郊区景观中的密度往往高于农村景观。然而，如果小型脊椎动物中间宿主不是城市浣熊饮食的重要组成部分，那么城市浣熊觅食行为的改变可能会影响浣熊贝蛔虫的传播。本研究的目的是在区域尺度上比较城市和农村浣熊种群中浣熊贝蛔虫的感染率。2000年至2005年9月至次年2月期间，从美国中西部七个州收集了204只浣熊进行尸检（区域样本）。在54%的被检查浣熊中发现了浣熊贝蛔虫。感染率在不同土地利用类型之间存在差异（卡方=11.56，自由度=1，P=0.0007），从农村地区收集的动物中感染率更高（65%），高于从城市地区收集的动物（41%）。感染强度也存在差异（F=5.52，自由度=1，P=0.02），农村浣熊的蠕虫负担（x=29.63±36.42）比城市浣熊（x=13.85±18.47）更重。尽管城市景观中浣熊密度很高，但感染浣熊贝蛔虫的城市浣熊较少，这表明对中间宿主作为食物来源的依赖减少。从三个芝加哥地区种群（本地样本）收集的浣熊子样本中的感染率也有类似趋势，这三个种群在1995年至2002年期间受到了密集监测，它们的城市化水平、种群密度和觅食行为各不相同，这支持了这一可能的解释。城市景观中浣熊贝蛔虫传播的减少可能是由于对中间宿主的捕食减少，幼年浣熊与浣熊贝蛔虫卵的接触可能是维持此类种群感染的一个重要因素。
