Surveillance for Ixodes scapularis and Ixodes pacificus ticks and their associated pathogens in Canada, 2019

Abstract

Background: The primary vectors of the agent of Lyme disease in Canada are Ixodes scapularis and Ixodes pacificus ticks. Surveillance for ticks and the pathogens they can transmit can inform local tick-borne disease risk and guide public health interventions. The objective of this article is to characterize passive and active surveillance of the main Lyme disease tick vectors in Canada in 2019 and the tick-borne pathogens they carry.

Methods: Passive surveillance data were compiled from the National Microbiology Laboratory Branch and provincial public health data sources. Active surveillance was conducted in selected sentinel sites in all provinces. Descriptive analysis of ticks submitted and infection prevalence of tick-borne pathogens are presented. Seasonal and spatial trends are also described.

Results: In passive surveillance, specimens of I. scapularis (n=9,858) were submitted from all provinces except British Columbia and I. pacificus (n=691) were submitted in British Columbia and Alberta. No ticks were submitted from the territories. The seasonal distribution pattern was bimodal for I. scapularis adults, but unimodal for I. pacificus adults. Borrelia burgdorferi was the most prevalent pathogen in I. scapularis (18.8%) and I. pacificus (0.3%). In active surveillance, B. burgdorferi was identified in 26.2% of I. scapularis; Anaplasma phagocytophilum in 3.4% of I. scapularis, and Borrelia miyamotoi and Powassan virus in 0.5% or fewer of I. scapularis. These same tick-borne pathogens were not found in the small number of I. pacificus tested.

Conclusion: This surveillance article provides a snapshot of the main Lyme disease vectors in Canada and their associated pathogens, which can be used to monitor emerging risk areas for exposure to tick-borne pathogens.

Keywords: Anaplasma; Babesia; Borrelia; Ixodes pacificus; Ixodes scapularis; surveillance.

Figure 1

Ixodes pacificus and Ixodes scapularis ticks submitted through passive tick surveillance, Canada, 2019^{a,b a} Each dot represents the probable location of acquisition for an I. pacificus (n=691) or I. scapularis (n=9,858) tick submitted through passive surveillance ^b No passive surveillance was conducted in Yukon, Northwest Territories or Nunavut for I. scapularis or I. pacificus ticks. Passive tick surveillance has been discontinued in the entire province of Nova Scotia, and some regions of Ontario and Québec; however, individuals could submit ticks directly to the National Microbiology Laboratory Branch from these jurisdictions

Figure 2

Number of Ixodes scapularis and Ixodes pacificus ticks submitted through passive surveillance, by month and tick instar, Canada, 2019^{a,b a} Data are presented for I. scapularis (n=9,797) and I. pacificus (n=690) ticks submitted through passive surveillance. Month of submission or tick instar was not available for I. scapularis (n=61) and I. pacificus (n=1) ^b No passive surveillance was conducted in Yukon, Northwest Territories or Nunavut for I. scapularis or I. pacificus ticks. Passive tick surveillance has been discontinued in the entire province of Nova Scotia, and some regions of Ontario and Québec; however, individuals could submit ticks directly to the National Microbiology Laboratory Branch from these jurisdictions

Figure 3

Ixodes pacificus and Ixodes scapularis ticks submitted through passive surveillance that were infected with Borrelia burgdorferi, Canada, 2019^{a,b,c a} Each dot represents the probable location of acquisition of at least one I. pacificus (n=2) or I. scapularis (n=1,819) single or multiple tick submission submitted through passive surveillance that was infected with B. burgdorferi ^b Lyme disease risk areas are identified by the provinces as of 2020 using the methods described in the 2016 national Lyme disease case definition (28)))) ^c No passive surveillance was conducted in Yukon, Northwest Territories or Nunavut for I. scapularis or I. pacificus ticks. Passive tick surveillance has been discontinued in the entire province of Nova Scotia, and some regions of Ontario and Québec; however, individuals could submit ticks directly to the National Microbiology Laboratory Branch from these jurisdictions

Figure 4

Ixodes scapularis ticks submitted through passive surveillance that were infected with Anaplasma phagocytophilum, Babesia microti and co-infections, Canada, 2019^{a,b a} Each symbol represents the probable location of acquisition of an I. scapularis single or multiple tick submission submitted through passive surveillance that tested positive for A. phagocytophilum (n=141), B. microti (n=13) or a co-infection (n=29). Co-infections were limited to only single submissions of I. scapularis, and include B. burgdorferi + A. phagocytophilum (n=26), B. burgdorferi + B. microti (n=2) and A. phagocytophilum + B. microti (n=1) ^b No passive surveillance was conducted in Yukon, Northwest Territories or Nunavut for I. scapularis or I. pacificus ticks. Passive tick surveillance has been discontinued in the entire province of Nova Scotia, and some regions of Ontario and Québec; however, individuals could submit ticks directly to the National Microbiology Laboratory Branch from these jurisdictions

Figure 5

Ixodes scapularis and Ixodes pacificus ticks with associated pathogens collected through active surveillance, Canada, 2019^{a,b a} Each symbol represents an active surveillance site where B. burgdorferi (n=38), A. phagocytophilum (n=12), B. miyamotoi (n=4), or Powassan virus (n=1) were found in I. scapularis ticks. There were 142 sites where no tick-borne pathogens were identified in ticks, including sites where no I. scapularis or I. pacificus were found (n=108). No active surveillance was conducted in Yukon, Northwest Territories or Nunavut for I. scapularis or I. pacificus ticks. The presence or absence of infected I. scapularis ticks is influenced by varying level of effort of active surveillance between provinces and seasonal variation when active surveillance took place. Infection prevalence should be interpreted with caution as not all active surveillance conducted in 2019 in Canada is included ^b Number of ticks tested: British Columbia (n=10), Alberta n=(0), Saskatchewan (n=0), Manitoba (n=3), Ontario (n=188–406 depending on pathogen), Québec (n=141), Newfoundland and Labrador (n=0), New Brunswick (n=194), Nova Scotia (n=169) and Prince Edward Island (n=2)