Institute of Biology, Laboratory of Eco-Epidemiology of Parasites, Université de Neuchâtel, Neuchâtel, Switzerland.
Vector Borne Zoonotic Dis. 2012 Aug;12(8):633-44. doi: 10.1089/vbz.2011.0763. Epub 2012 May 18.
We compared Ixodes ricinus questing density, the infestation of rodents by immature stages, and the diversity of Borrelia burgdorferi sensu lato (sl) in questing ticks and ticks collected from rodents in two Lyme borreliosis (LB)-endemic areas in Switzerland (Portes-Rouges [PR] and Staatswald [SW]) from 2003 to 2005. There were variations in the seasonal pattern of questing tick densities among years. Questing nymphs were globally more abundant at PR than at SW, but the proportion of rodents infested by immature ticks was similar (59.4% and 61%, respectively). Questing tick activity lasted from February to November with a strong decline in June. The seasonal pattern of ticks infesting rodents was different. Ticks infested rodents without decline in summer, suggesting that the risk of being bitten by ticks remains high during the summer. Rodents from SW showed the highest infestation levels (10±21.6 for larvae and 0.54±1.65 for nymphs). The proportion of rodents infested simultaneously by larvae and nymphs (co-feeding ticks) was higher at SW (28%) than at PR (11%). Apodemus flavicollis was the species the most frequently infested by co-feeding ticks, and Myodes glareolus was the most infective rodent species as measured by xenodiagnosis. At PR, the prevalence of B. burgdorferi sl in questing ticks was higher (17.8% for nymphs and 32.4% for adults) than at SW (10.4% for nymphs and 24.8% for adults), with B. afzelii as the dominant species, but B. garinii, B. burgdorferi sensu stricto, and B. valaisiana were also detected. Rodents transmitted only B. afzelii (at PR and at SW) and B. bavariensis (at SW) to ticks, and no mixed infection by additional genospecies was observed in co-feeding ticks. This implies that co-feeding transmission does not contribute to genospecies diversity. However, persistent infections in rodents and co-feeding transmission contribute to the perpetuation of B. afzelii in nature.
我们比较了 2003 年至 2005 年瑞士两个莱姆病（LB）流行地区（Portes-Rouges [PR]和Staatswald [SW]）中游离若蜱密度、幼蜱感染啮齿动物的情况以及游离蜱和从啮齿动物中收集的蜱中伯氏疏螺旋体（sl）的多样性。几年来，游离若蜱密度的季节性模式存在变化。PR 的游离若虫总体上比 SW 更丰富，但受幼蜱感染的啮齿动物比例相似（分别为 59.4%和 61%）。游离若虫的活动从 2 月持续到 11 月，6 月急剧下降。感染啮齿动物的蜱季节性模式不同。夏季蜱的感染没有下降，这表明夏季被蜱叮咬的风险仍然很高。来自 SW 的啮齿动物感染水平最高（幼虫为 10±21.6，若虫为 0.54±1.65）。同时感染幼虫和若虫（共食蜱）的啮齿动物比例在 SW（28%）高于 PR（11%）。共食蜱感染最频繁的物种是黄腹草原田鼠，而通过皮肤移植物法检测到最具感染性的啮齿动物物种是黑线姬鼠。在 PR，游离若蜱中伯氏疏螺旋体 sl 的流行率较高（幼虫为 17.8%，成虫为 32.4%），高于 SW（幼虫为 10.4%，成虫为 24.8%），优势种为伯氏疏螺旋体 afzelii，但也检测到伯氏疏螺旋体 garinii、伯氏疏螺旋体 stricto 和伯氏疏螺旋体 valaisiana。啮齿动物仅向蜱传播伯氏疏螺旋体 afzelii（在 PR 和 SW）和伯氏疏螺旋体 bavariensis（在 SW），在共食蜱中未观察到其他共生种的混合感染。这意味着共食传播不会导致共生种多样性增加。然而，啮齿动物的持续性感染和共食传播有助于伯氏疏螺旋体 afzelii 在自然界中的持续存在。
