Baxter Lindsay, Lubelczyk Charles, Harrington Laura C, Angelico Jake, Meagher Molly C, Smith Robert P, Robich Rebecca M
Cornell University College of Agriculture and Life Sciences, Ithaca, New York.
MaineHealth Institute for Research Lyme and Vector-Borne Disease Laboratory, Scarborough, Maine.
Am J Trop Med Hyg. 2024 Jul 30;111(6):1302-1310. doi: 10.4269/ajtmh.23-0532. Print 2024 Dec 4.
Powassan virus lineage II or deer tick virus (DTV) is a rare but increasingly reported human infection in the United States transmitted by Ixodes scapularis ticks. The virus is thought to be maintained in environmental foci that are optimal for tick and vertebrate reservoirs, but details on DTV ecology are poorly understood. We investigated DTV tick infection rates and reservoir host abundance in a focus of consistent DTV activity in Maine, USA. Host and tick abundance, vegetation, and microclimate conditions were measured in three forest sites representing increasing invasive understory infestation. Sites were selected representing native understory, mixed vegetation with some invasive Japanese barberry (Berberis thunbergii), and a highly invasive site dominated by Japanese barberry. Japanese barberry in the mixed vegetation site averaged 1 m in height with space between plants, whereas the highly invasive site had impenetrable Japanese barberry over 1.5 m. The DTV infection rate was greater in the highly invasive site. Density of I. scapularis ticks were significantly lower in the native forest site, and no DTV was found. Another feature of the DTV focus was more stable humid microclimate throughout the year compared with the other sites and a nearby continuous section of forest, consistent with reports from Connecticut, USA. We conclude that invasive Japanese barberry stands provide favorable and consistent microclimate conditions to maintain high DTV infection rates annually among questing I. scapularis ticks. Understanding environmental and landscape features that support high infection rates could lead to the identification of high-risk habitats for contracting DTV.
波瓦桑病毒II系或鹿蜱病毒（DTV）是一种在美国罕见但报告病例日益增多的人类感染病毒，通过肩突硬蜱传播。该病毒被认为在对蜱虫和脊椎动物宿主适宜的环境疫源地中存续，但人们对DTV生态学的细节了解甚少。我们在美国缅因州一个持续有DTV活动的疫源地调查了DTV在蜱虫中的感染率以及宿主的丰富度。在三个代表林下植被入侵程度不断增加的森林地点测量了宿主和蜱虫的丰富度、植被以及小气候条件。所选择的地点分别代表原生林下植被、含有一些入侵性日本小檗（小檗）的混合植被以及以日本小檗为主的高度入侵地点。混合植被地点的日本小檗平均高度为1米，植株之间有间距，而高度入侵地点有超过1.5米高、无法穿越的日本小檗。在高度入侵地点，DTV感染率更高。原生森林地点肩突硬蜱的密度显著更低，且未发现DTV。与其他地点以及附近一段连续森林相比，该DTV疫源地的另一个特点是全年小气候更稳定湿润，这与美国康涅狄格州的报告一致。我们得出结论，入侵性日本小檗林提供了有利且稳定的小气候条件，使得每年在觅食的肩突硬蜱中保持较高的DTV感染率。了解支持高感染率的环境和景观特征可能有助于识别感染DTV的高风险栖息地。
