Bournez Laure, Umhang Gerald, Moinet Marie, Boucher Jean-Marc, Demerson Jean-Michel, Caillot Christophe, Legras Léo, Devillers Elodie, Hansmann Yves, Velay Aurélie, Richomme Céline, Moutailler Sara, Boué Franck
Nancy Laboratory for Rabies and Wildlife, The French Agency for Food, Environmental and Occupational Health & Safety (ANSES), CS 40009, 54220 Malzéville, France.
Unité Mixte de Recherche Biologie Moléculaire et Immunologie Parasitaire (UMR BIPAR), ANSES, INRAE, Ecole Nationale Vétérinaire d'Alfort, Paris-Est Sud, 94700 Maisons-Alfort, France.
Pathogens. 2020 Nov 10;9(11):930. doi: 10.3390/pathogens9110930.
Tick-borne encephalitis virus (TBEV) depends mainly on a fragile mode of transmission, the co-feeding between infected nymphs and larvae on rodents, and thus persists under a limited set of biotic and abiotic conditions. If these conditions change, natural TBEV foci might be unstable over time. We conducted a longitudinal study over seven years in a mountain forest in Alsace, Eastern France, located at the western border of known TBEV distribution. The objectives were (i) to monitor the persistence of TBEV circulation between small mammals and ticks and (ii) to discuss the presence of TBEV circulation in relation to the synchronous activity of larvae and nymphs, to the densities of questing nymphs and small mammals, and to potential changes in meteorological conditions and deer densities. Small mammals were trapped five times per year from 2012 to 2018 to collect blood samples and record the presence of feeding ticks, and were then released. Questing nymphs were collected twice a year. Overall, 1344 different small mammals ( and ) were captured and 2031 serum samples were tested for the presence of antibodies against TBEV using an in-house ELISA. Seropositive rodents (2.1%) were only found from 2012 to 2015, suggesting that the virus disappeared afterwards. In parallel, we observed unusual variations in inter-annual nymph abundance and intra-annual larval activity that could be related to exceptional meteorological conditions. Changes in the densities of questing nymphs and deer associated with the natural stochastic variations in the frequency of contacts between rodents and infected ticks may have contributed to the endemic fadeout of TBEV on the study site. Further studies are needed to assess whether such events occur relatively frequently in the area, which could explain the low human incidence of TBE in Alsace and even in other areas of France.
蜱传脑炎病毒（TBEV）主要依赖一种脆弱的传播方式，即受感染的若虫和幼虫在啮齿动物身上共同取食，因此仅在有限的一组生物和非生物条件下持续存在。如果这些条件发生变化，自然的TBEV疫源地可能会随时间变得不稳定。我们在法国东部阿尔萨斯的一片山林中进行了为期七年的纵向研究，该山林位于已知TBEV分布的西部边界。研究目的是：（i）监测TBEV在小型哺乳动物和蜱之间的循环持续性；（ii）讨论TBEV循环的存在与幼虫和若虫的同步活动、宿主若虫和小型哺乳动物的密度以及气象条件和鹿密度的潜在变化之间的关系。从2012年到2018年，每年对小型哺乳动物进行五次诱捕，以采集血样并记录附着蜱的存在情况，然后将其放生。每年对宿主若虫进行两次采集。总共捕获了1344只不同的小型哺乳动物（和），并使用内部酶联免疫吸附测定法（ELISA）对2031份血清样本进行了TBEV抗体检测。仅在2012年至2015年期间发现了血清阳性啮齿动物（2.1%），这表明该病毒此后消失了。与此同时，我们观察到年度间若虫数量和年度内幼虫活动的异常变化，这可能与异常气象条件有关。宿主若虫和鹿的密度变化与啮齿动物和受感染蜱之间接触频率的自然随机变化相关，这可能导致了研究地点TBEV的地方病消失。需要进一步研究来评估此类事件在该地区是否相对频繁发生，这可以解释阿尔萨斯乃至法国其他地区人类TBE发病率较低的原因。
