Crucially, the data included uncertainty information in meters for geographic coordinates, summarizing the likely area across which each of the ticks was likely collected. Geographic coordinate information was generated previously by WRBU using standard methods, including Biogeomancer ( ) and the MANIS georeferencing protocol ( ). The ticks were identified morphologically by entomologists using standard taxonomic keys for North American tick identification. americanum that were questing or attached to military personnel. This dataset had collection records from 1995–2015, and included all life stages of A. Locations within North America where lone star ticks have been collected (and positively identified) were made available for this study in digital format by the Walter Reed Biosystematics Unit (WRBU). We evaluated these scenarios via model outputs from 4 different general circulation models (GCMs) to permit detailed assessment of uncertainty in model predictions. We used ecological niche modeling approaches under two scenarios of greenhouse gas emissions and consequent climate change: Representative Concentration Pathway (RCP) 4.5, representing medium-to-low emissions levels, and RCP 8.5, representing a high emissions scenario. Here, we have assessed the spatial distribution of lone star ticks in North America under present climate conditions, with the goal of understanding and anticipating its potential distribution under future climate scenarios. We note that this model failure is parallel to one on which we have remarked previously, as regards the western limits of the range of Ixodes scapularis which was related to erroneous assumptions in the process of model thresholding. The western edge of the current distribution described in their study, however, falls well short of areas from which we have routinely collected ticks in Kansas and Nebraska over the years, albeit at relatively low abundances. (2015) presented an ensemble spatial distribution model for current and future distributions of lone star ticks in the conterminous United States. Our earlier analyses of ecological niches and geographic distributions of lone star ticks in Kansas indicated a westward range expansion compared to the CDC map. In fact, our own surveys in Kansas, Oklahoma, and Nebraska over the past five years have yielded numerous records of all questing life stages of lone star ticks throughout the tick season (mid-April through mid-August), well outside the “known” distributional area, indicating that the ticks are well established in areas where they were presumed to be absent in the recent past. This tick probably has expanded and/or shifted its range owing to non-stationary drivers such as climate change and the population explosion in white-tailed deer ( Odocoileus virginianus) populations. The methods used to identify this range limit are not fully clear, and this map is described as providing only broad guidance it was based on multiple surveys, some dating as far back as the 1940s. Reports of infections outside such endemic areas may relate to travel from endemic areas or misdiagnosis, but may also indicate range expansion of vector species into new regions.Ĭurrently, the leading edge of the geographic distribution of lone star ticks is considered to lie in the central midwestern United States. Many vector-borne disease infections occur within geographic areas that are highly concordant with the range of transmitting, pathogen-infected vector species this point likely holds true also for infections vectored by lone star ticks. It has been implicated in transmission of several pathogens known to cause morbidity and mortality to humans and companion animals. The medically significant tick species, Amblyomma americanum (Linn.) (Acari: Ixodidae), commonly known as the lone star tick, is distributed widely across the eastern United States.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |