Different Ecological Niches for Ticks of Public Health Significance in Canada

Abstract

Tick-borne diseases are a growing public health concern as their incidence and range have increased in recent decades. Lyme disease is an emerging infectious disease in Canada due to northward expansion of the geographic range of Ixodes scapularis, the principal tick vector for the Lyme disease agent Borrelia burgdorferi, into central and eastern Canada. In this study the geographical distributions of Ixodid ticks, including I. scapularis, and environmental factors associated with their occurrence were investigated in New Brunswick, Canada, where few I. scapularis populations have been found to date. Density of host-seeking ticks was evaluated by drag sampling of woodland habitats in a total of 159 sites. Ixodes scapularis ticks (n = 5) were found on four sites, Ixodes muris (n = 1) on one site and Haemaphysalis leporispalustris (n = 243) on 41 sites. One of four adult I. scapularis ticks collected was PCR-positive for B. burgdorferi. No environmental variables were significantly associated with the presence of I. scapularis although comparisons with surveillance data in neighbouring provinces (Québec and Nova Scotia) suggested that temperature conditions may be too cold for I. scapularis (< 2800 annual degree days above 0°C [DD > 0°C]) across much of New Brunswick. In contrast, the presence of H. leporispalustris, which is a competent vector of tularaemia, was significantly (P < 0.05) associated with specific ranges of mean DD > 0°C, mean annual precipitation, percentage of clay in site soil, elevation and season in a multivariable logistic regression model. With the exception of some localized areas, temperature conditions and deer density may be too low for the establishment of I. scapularis and Lyme disease risk areas in New Brunswick, while environmental conditions were suitable for H. leporispalustris at many sites. These findings indicate differing ecological niches for two tick species of public health significance.

Expansion of the Lyme Disease Vector Ixodes Scapularis in Canada Inferred from CMIP5 Climate Projections

“…The NARR has already been used as reference for other reanalysis projects including the California Reanalysis Downscaling at 10 km (CaRD10) ( Kanamaru and Kanamitsu 2007 ). Other studies also support the use of the NARR for the analysis of climate processes ( Fall et al 2010 ). Following CMIP-WGCM-WGSIP (2011) , we used the NARR surface air temperature to estimate the bias of each GCM’s surface air temperature data at each grid point.…”

Detecting and Attributing Health Burdens to Climate Change

“…Other studies using the same sites or sampling sites in the region found consistent positive associations between the presence and abundance of I. scapularis ticks on animal hosts (rodents and deer) and temperature, accounting for a range of alternative potential drivers for tick occurrence including habitat, rodent host abundance, rodent host species diversity, animal-level variables (e.g., age, sex, reproductive status), deer density, rainfall, and the possibility of spatial autocorrelation ( Bouchard et al 2013a ; Bouchard et al 2013b ). Further field surveillance data in eastern Canada supported the importance of temperature in determining the spatial pattern of establishment of I. scapularis at a multiprovince geographic scale in eastern Canada ( Gabriele-Rivet et al 2015 ).…”

A 117 year retrospective analysis of Pennsylvania tick community dynamics

“…Since the submissions for tick identification after 1990 were mostly limited to ticks removed from humans or their domestic animals, there is insufficient power to detect this species. Farther north and west, Hlp is still found parasitizing a wide range of avian and mammalian hosts [63,64].…”