Surveillance for Ixodes scapularis and Ixodes pacificus ticks and their associated pathogens in Canada, 2020

Abstract

Background: Ixodes scapularis and Ixodes pacificus ticks are the principal vectors of the agent of Lyme disease and several other tick-borne diseases in Canada. Tick surveillance data can be used to identify local tick-borne disease risk areas and direct public health interventions. The objective of this article is to describe the seasonal and spatial characteristics of the main Lyme disease vectors in Canada, and the tick-borne pathogens they carry, using passive and active surveillance data from 2020.

Methods: Passive and active surveillance data were compiled from the National Microbiology Laboratory Branch (Public Health Agency of Canada), provincial and local public health authorities, and eTick (an online, image-based platform). Seasonal and spatial analyses of ticks and their associated pathogens are presented, including infection prevalence estimates.

Results: In passive surveillance, I. scapularis (n=7,534) were submitted from all provinces except Manitoba and British Columbia, while I. pacificus (n=718) were submitted only from British Columbia. No ticks were submitted from the Territories. The seasonal distribution of I. scapularis submissions was bimodal, but unimodal for I. pacificus. Four tick-borne pathogens were identified in I. scapularis (Borrelia burgdorferi, Anaplasma phagocytophilum, Babesia microti and Borrelia miyamotoi) and one in I. pacificus (B. miyamotoi). In active surveillance, I. scapularis (n=688) were collected in Ontario, Québec and New Brunswick. Five tick-borne pathogens were identified: B. burgdorferi, A. phagocytophilum, B. microti, B. miyamotoi and Powassan virus.

Conclusion: This article provides a snapshot of the distribution of I. scapularis and I. pacificus and their associated human pathogens in Canada in 2020, which can help assess the risk of exposure to tick-borne pathogens in different provinces.

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

Figure 1

Ixodes pacificus and Ixodes scapularis ticks submitted through passive tick surveillance, Canada, 2020^{a a} Each dot represents the probable location of acquisition for an I. pacificus (n=718) or I. scapularis (n=7,397) tick submitted through passive surveillance. Ticks from Alberta Health were mapped to the centroid of the forward sortation area (first three characters of the postal code) of acquisition. One hundred and thirty-seven ticks were not mapped because the probable location of acquisition could not be determined

Figure 2

Number of Ixodes pacificus and Ixodes scapularis ticks submitted through passive surveillance, by month and tick instar, Canada, 2020^{a a} Data are presented for I. pacificus (n=718) and I. scapularis (n=6,755) ticks submitted through passive surveillance. Month of submission or tick instar was not available for I. scapularis (n=779)

Figure 3

Ixodes scapularis ticks submitted through passive surveillance infected with Borrelia burgdorferi, Canada, 2020^{a,b a} Each dot represents the probable location of acquisition of at least one I. scapularis (n=860) single or multiple tick submission submitted through passive surveillance that was infected with B. burgdorferi. Eight ticks were not mapped because the probable location of acquisition could not be determined ^b Lyme disease risk areas are identified by the provinces as of 2021 using the methods described in the 2016 national Lyme disease case definition ((22)). On the map, risk areas are identified as hatched gray areas

Figure 4

Ixodes pacificus and Ixodes scapularis ticks submitted through passive surveillance infected with Anaplasma phagocytophilum, Babesia microti, Borrelia miyamotoi and co-infections, Canada, 2020^{a a} Each symbol represents the probable location of acquisition of an I. pacificus (n=1) or I. scapularis (n=67) single or multiple tick submission submitted through passive surveillance that tested positive for A. phagocytophilum (n=42), B. microti (n=1), B. miyamotoi (n=25) or a co-infection (n=14). Co-infections were limited to only single submissions of ticks and include B. burgdorferi + B. miyamotoi (n=7), B. burgdorferi + A. phagocytophilum (n=6) and A. phagocytophilum + B. miyamotoi (n=1) all in I. scapularis. Two ticks with A. phagocytophilum and one tick with B. miyamotoi were not mapped because the probable location of acquisition could not be determined

Figure 5

Ixodes scapularis ticks with associated pathogens collected through active surveillance, Canada, 2020^{a,b a} Each symbol represents an active surveillance site where A. phagocytophilum (n=31), B. microti (n=1), B. burgdorferi (n=200), B. miyamotoi (n=3), or Powassan virus (n=1) were found in I. scapularis ticks. There were 17 sites where no tick-borne pathogens were identified in I. scapularis ticks ^b Number of ticks tested: Ontario (n=128), Québec (n=110) and New Brunswick (n=445)