Ixodes scapularisTicks Collected by Passive Surveillance in Canada: Analysis of Geographic Distribution and Infection with Lyme Borreliosis AgentBorrelia burgdorferi

Abstract

Passive surveillance for the occurrence of the tick Ixodes scapularis Say (1821) and their infection with the Lyme borreliosis spirochaetes Borrelia burgdorferi s.l. has taken place in Canada since early 1990. Ticks have been submitted from members of the public, veterinarians, and medical practitioners to provincial, federal, and university laboratories for identification, and the data have been collated and B. burgdorferi detected at the National Microbiology Laboratory. The locations of collection of 2,319 submitted I. scapularis were mapped, and we investigated potential risk factors for I. scapularis occurrence (in Quebec as a case study) by using regression analysis and spatial statistics. Ticks were submitted from all provinces east of Alberta, most from areas where resident I. scapularis populations are unknown. Most were adult ticks and were collected in spring and autumn. In southern Québec, risk factors for tick occurrence were lower latitude and remote-sensed indices for land cover with woodland. B. burgdorferi infection, identified by conventional and molecular methods, was detected in 12.5% of 1,816 ticks, including 10.1% of the 256 ticks that were collected from humans and tested. Our study suggests that B. burgdorferi-infected I. scapularis can be found over a wide geographic range in Canada, although most may be adventitious ticks carried from endemic areas in the United States and Canada by migrating birds. The risk of Lyme borreliosis in Canada may therefore be mostly low but more geographically widespread than previously suspected.

Linkages of Weather and Climate WithIxodes scapularisandIxodes pacificus(Acari: Ixodidae), Enzootic Transmission ofBorrelia burgdorferi, and Lyme Disease in North America

“…Ticks require three conditions for their persistence: 1) a suitable climate for completion of their life cycle and host-seeking activity; 2) a suitable habitat that protects ticks from weather or other abiotic extremes that may kill them; and 3) suitable densities of host species from which to take bloodmeals. For I. scapularis there is evidence that populations at the northern limit of the range, and their rates of spread there, are limited by temperature in a way that has been predicted by simulation models of the effects of temperature on tick survival via effects on tick life cycle length (Ogden et al 2006a,b, 2008a, 2014; Leighton et al 2012; Bouchard et al 2013b). To the west, low rainfall and humidity prevent I. scapularis from establishing in open prairie habitats, although they can persist in woodlands bordering on the prairie (Rydzewski et al 2011, Rynkiewicz and Clay 2014) and perhaps along riparian corridors in prairie habitats.…”

Population-Based Passive Tick Surveillance and Detection of Expanding Foci of Blacklegged Ticks Ixodes scapularis and the Lyme Disease Agent Borrelia burgdorferi in Ontario, Canada

“…The core elements of the passive surveillance system developed at the NML are similar to those used at PHOL and were described previously [13]. The primary differences between the two surveillance systems is that NML asks specifically for information about the locality of tick acquisition (and not just residence of submitter) and submitter's travel history, while recording the tick's engorgement status, life-cycle stage and pathogen test results.…”

“…In response to discoveries of B . burgdorferi -infected blacklegged ticks in southern Ontario in 1987, a national passive tick surveillance program began in 1990 focusing on blacklegged ticks, whereby ticks were submitted from the public through public health authorities and health care professionals for identification and pathogen detection [12], [13]. Here we investigate ticks submitted for identification and testing from 2008 through 2012 in Ontario, Canada.…”

Inter-Model Comparison of the Landscape Determinants of Vector-Borne Disease: Implications for Epidemiological and Entomological Risk Modeling

“…Scaled NDVI data for June 10–25, 2001, the time period used in the original analysis [9], were obtained from the Global Land Cover Facility and were converted to true NDVI values following methods detailed elsewhere [30]. Human population data were obtained from the U.S. Census Bureau at county-level resolution for the year 2000 [24].…”

“…Examples of quantitative information routinely drawn from previous work include mathematical models and their parameters, dose-response functions, and thresholds and other parameter estimates [1], [3]. Common applications of such information include health impact assessments [4], [5], ecological risk assessments [6], [7], and risk mapping of disease vectors [8], [9].…”