Northward range expansion of Ixodes scapularis evident over a short timescale in Ontario, Canada

Abstract

The invasion of the blacklegged tick, Ixodes scapularis into Ontario, Canada poses a significant risk to public health because it is a vector for numerous pathogens, including Borrelia burgdorferi sensu stricto, the causative agent of Lyme disease. Baseline field sampling in 2014 and 2015 detected I. scapularis and B. burgdorferi at sites across southern, eastern and central Ontario, including a hot spot in eastern Ontario. A “speed of spread” model for I. scapularis developed by Leighton and colleagues (2012) estimated that the tick’s range was expanding northward at 46 km/year. In 2016, we revisited a subset of sites sampled in 2014 and 2015 to understand the changing nature of risk, and assess whether the rate of tick invasion is consistent with the speed of spread estimate. Ticks were collected via tick dragging at 17 out of 36 sites, 5 of which were new sites for I. scapularis. Samples were positive for B. burgdorferi at 8 sites. No other I. scapularis-borne pathogens were detected. Centrographic statistics revealed an increase in the dispersion of I. scapularis positive sites in eastern Ontario. Field data for each site were then compared to the model’s predicted year of establishment for each census subdivision. Our findings illustrate that the range expansion of I. scapularis and the emergence of B. burgdorferi is ongoing, and provide short timescale evidence of the processes associated with I. scapularis spread. The range front appears to be moving at a rate of ~46 km/year, with colonization of the tick behind this range front occurring at a slower and heterogeneous rate. Assessment of site-level ecological factors did not provide any insight into the underlying processes that may be influencing the colonization of I. scapularis in specific areas. Ongoing field sampling is needed to monitor this dynamic process. This study highlights the current geographic risk associated with Lyme disease, which can be used to target public health interventions to the areas of greatest risk.

Lyme Disease Emergence after Invasion of the Blacklegged Tick,Ixodes scapularis, Ontario, Canada, 2010–2016

“…Time to first case was significantly associated with time to first reported I. scapularis tick (adjusted r 2  = 0.56; p<0.001) and time to first B. burgdorferi –infected tick (adjusted r 2  = 0.67; p<0.001) after adjusting for distance to the FSA with highest LD incidence in 2010. The associated lag between each phase of ≈1 year supports the hypothesis that invasion and establishment of tick populations is followed by colonization of B. burgdorferi ( 12 ), or it might reflect the arrival of infected ticks with subsequent increase in B. burgdorferi prevalence. However, drawing conclusions on the exact timing of tick and pathogen invasion is difficult because of the nature of passive surveillance data.…”

“…By comparison, these rates are still far below the ≈110 cases/100,000 population observed in the bordering St. Lawrence County of New York state ( 15 ). Given the ongoing emergence process, LD incidence will likely continue to increase in eastern Ontario as I. scapularis tick populations and B. burgdorferi continue to establish and fill in suitable habitats ( 12 ). This pattern highlights the importance of fine-scale studies to identify patterns and determinants of LD and other tickborne pathogens in different regions and populations.…”

Parasites of seabirds: A survey of effects and ecological implications

“…Despite having now been isolated from dozens of wild terrestrial birds, the effects of B. burgdorferi in these populations is not well understood. Most research on bird-tick systems studying the disease focus on the role of wild birds as reservoirs, with the potential to spread it across large spatial scales (Clow et al, 2017;Smith et al, 1996).…”

Utilisation des images d'observation de la terre pour améliorer la cartographie des risques de maladies associées au changement climatiques

“…Le climat a un impact direct sur les mouvements des populations humaines et des vecteurs de maladies infectieuses, tels que les tiques et les moustiques, et sur leurs populations hôtes (12,13). L'augmentation de la température et la variabilité du climat entraînent une augmentation et une expansion géographique des populations de vecteurs et des maladies qu'ils transmettent (1,7,11,(14)(15)(16)(17)(18)(19)(20)(21)(22). Par exemple, de nombreuses études ont démontré l'expansion des tiques vers le Nord, ce qui a été associé à une augmentation constante du nombre de cas de la maladie de Lyme chez l'humain (23)(24)(25).…”