1 Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo , PO Box 1066, Blindern, 0316 Oslo , Norway.
2 Evolutionary Ecology Group, Department of Biology, University of Antwerp , Universiteitsplein 1, 2610 Wilrijk , Belgium.
Proc Biol Sci. 2019 May 29;286(1903):20190759. doi: 10.1098/rspb.2019.0759.
Many vector-borne diseases are transmitted through complex pathogen-vector-host networks, which makes it challenging to identify the role of specific host groups in disease emergence. Lyme borreliosis in humans is now the most common vector-borne zoonosis in the Northern Hemisphere. The disease is caused by multiple genospecies of Borrelia burgdorferi sensu lato bacteria transmitted by ixodid (hard) ticks, and the major host groups transmit Borrelia genospecies with different pathogenicity, causing variable clinical symptoms in humans. The health impact of a given host group is a function of the number of ticks it infects as well as the pathogenicity of the genospecies it carries. Borrelia afzelii, with mainly small mammals as reservoirs, is the most common pathogen causing Lyme borreliosis, and it is often responsible for the largest proportion of infected host-seeking tick nymphs in Europe. The bird-borne Borrelia garinii, though less prevalent in nymphal ticks, is more likely to cause Lyme neuroborreliosis, but whether B. garinii causes disseminated disease more frequently has not been documented. Based on extensive data of annual disease incidence across Norway from 1995 to 2017, we show here that 69% of disseminated Lyme borreliosis cases were neuroborreliosis, which is three times higher than predicted from the infection prevalence of B. garinii in host-seeking ticks (21%). The population estimate of migratory birds, mainly of thrushes, explained part of the annual variation in cases of neuroborreliosis, with a one-year time lag. We highlight the important role of the genospecies' pathogenicity and the host associations for understanding the epidemiology of disseminated Lyme borreliosis.
许多虫媒传染病是通过复杂的病原体-媒介-宿主网络传播的，这使得确定特定宿主群体在疾病出现中的作用具有挑战性。人类莱姆病现在是北半球最常见的虫媒动物传染病。该病由伯氏疏螺旋体多种基因型细菌引起，通过硬蜱传播，主要宿主群体传播具有不同致病性的伯氏疏螺旋体基因型，导致人类出现不同的临床症状。给定宿主群体的健康影响是其感染的蜱数量以及携带的基因型致病性的函数。以小型哺乳动物为主要宿主的阿费尔森螺旋体（Borrelia afzelii）是引起莱姆病的最常见病原体，它通常是欧洲感染宿主寻求的蜱若虫中感染比例最大的病原体。虽然鸟类传播的伯氏疏螺旋体（Borrelia garinii）在若虫蜱中的流行程度较低，但更有可能引起莱姆神经Borreliosis，但伯氏疏螺旋体（Borrelia garinii）是否更频繁地引起播散性疾病尚未有记录。根据 1995 年至 2017 年挪威年度疾病发病率的广泛数据，我们在这里表明，69%的播散性莱姆病病例为神经莱姆病，这是从宿主寻求的蜱中伯氏疏螺旋体（Borrelia garinii）感染率（21%）预测的三倍。候鸟的种群估计，主要是画眉，解释了神经莱姆病病例年度变化的一部分，具有一年的时间滞后。我们强调了基因型致病性和宿主关联在理解播散性莱姆病流行病学中的重要作用。
