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

Abstract

Background:A number of studies have assessed possible climate change impacts on the Lyme disease vector, Ixodes scapularis. However, most have used surface air temperature from only one climate model simulation and/or one emission scenario, representing only one possible climate future.Objectives:We quantified effects of different Representative Concentration Pathway (RCP) and climate model outputs on the projected future changes in the basic reproduction number (normalR0) of I. scapularis to explore uncertainties in future normalR0 estimates.Methods:We used surface air temperature generated by a complete set of General Circulation Models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) to hindcast historical (1971–2000), and to forecast future effects of climate change on the normalR0 of I. scapularis for the periods 2011–2040 and 2041–2070.Results:Increases in the multimodel mean normalR0 values estimated for both future periods, relative to 1971–2000, were statistically significant under all RCP scenarios for all of Nova Scotia, areas of New Brunswick and Quebec, Ontario south of 47°N, and Manitoba south of 52°N. When comparing RCP scenarios, only the estimated normalR0 mean values between RCP6.0 and RCP8.5 showed statistically significant differences for any future time period.Conclusion:Our results highlight the potential for climate change to have an effect on future Lyme disease risk in Canada even if the Paris Agreement’s goal to keep global warming below 2°C is achieved, although mitigation reducing emissions from RCP8.5 levels to those of RCP6.0 or less would be expected to slow tick invasion after the 2030s. https://doi.org/10.1289/EHP57

Impact of recent and future climate change on vector‐borne diseases

“…The incidence of Lyme disease has increased from 0.4 to 2.7 per 100,000 population from 2009 to 2016 in Canada; 88% of cases were reported in the provinces of Quebec, Ontario, and Nova Scotia . Even under an optimistic climate change scenario, for which the global warming increase is limited to 1.5 °C, consistent with the Paris agreement target, Lyme disease was found in simulations to spread farther north in Canada in the future . Northern Russia has also experienced an increase in the Ixodes tick population and in TBE cases over the past decades .…”

“…159 Even under an optimistic climate change scenario, for which the global warming increase is limited to 1.5°C, consistent with the Paris agreement target, Lyme disease was found in simulations to spread farther north in Canada in the future. 160 Northern Russia has also experienced an increase in the Ixodes tick population and in TBE cases over the past decades. 161,162 In particular, a 50-fold rise in TBE incidence was reported for the far northern province of Arkhangelsk Oblast during the 2000s compared with the 1980s.…”

Estimating direct healthcare costs attributable to laboratory‐confirmed Lyme disease in Ontario, Canada: A population‐based matched cohort study using health administrative data

“…In Canada, the first blacklegged ticks were reported in the 1970s, followed by a range expansion in the mid‐1990s along the northern shore of Lake Erie, Lake Ontario, and the St. Lawrence River which triggered public health action in 2005 to implement provincial surveillance on the emerging vector‐borne disease in Ontario. The incidence of LD has continued to rise over the last decade, and climate projections estimate future range expansion of the blacklegged tick will continue over the next decade to further increase the risk of LD in Canada (Gasmi et al, ; McPherson et al, ).…”

Risk assessment strategies for early detection and prediction of infectious disease outbreaks associated with climate change

“…birds, rodents and deer) that participate in the transmission of pathogens from ticks and mosquitoes to humans as climate suitability for vector and reservoir populations change (5,6). For example, the increase in cases of Lyme disease in Canada reflect the northward expansion of the range of the black-legged tick vector, Ixodes scapularis, in the United States (US) and into southern Canada, as climate change has made Canada more conducive to establishing tick populations (7,8). This expansion of the area where the vectors and their reservoirs can thrive means not only an increased risk of sporadic infectious disease but also an increased likelihood that these vectors, and the diseases that they carry, can become endemic (6,(9)(10)(11).…”