A multi-year assessment of blacklegged tick (Ixodes scapularis) population establishment and Lyme disease risk areas in Ottawa, Canada, 2017-2019

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DOI

https://doi.org/ 10.1371/journal.pone.0246484

Language of the publication
English
Date
2021-02-04
Type
Article
Author(s)
  • Burrows, Holly
  • Talbot, Benoit
  • McKay, Roman
  • Slatculescu, Andreea
  • Logan, James
  • Thickstun, Charles
  • Lindsay, Robbin
  • Dibernardo, Antonia
  • Koffi, Jules K.
  • Ogden, Nicholas H.
  • Kulkarni, Manisha A.
Publisher
PLOS

Abstract

Canadians face an emerging threat of Lyme disease due to the northward expansion of the tick vector, Ixodes scapularis. We evaluated the degree of I. scapularis population establishment and Borrelia burgdorferi occurrence in the city of Ottawa, Ontario, Canada from 2017–2019 using active surveillance at 28 sites. We used a field indicator tool developed by Clow et al. to determine the risk of I. scapularis establishment for each tick cohort at each site using the results of drag sampling. Based on results obtained with the field indicator tool, we assigned each site an ecological classification describing the pattern of tick colonization over two successive cohorts (cohort 1 was comprised of ticks collected in fall 2017 and spring 2018, and cohort 2 was collected in fall 2018 and spring 2019). Total annual site-specific I. scapularis density ranged from 0 to 16.3 ticks per person-hour. Sites with the highest density were located within the Greenbelt zone, in the suburban/rural areas in the western portion of the city of Ottawa, and along the Ottawa River; the lowest densities occurred at sites in the suburban/urban core. B. burgdorferi infection rates exhibited a similar spatial distribution pattern. Of the 23 sites for which data for two tick cohorts were available, 11 sites were classified as “high-stable”, 4 were classified as “emerging”, 2 were classified as “low-stable”, and 6 were classified as “non-zero”. B. burgdorferi-infected ticks were found at all high-stable sites, and at one emerging site. These findings suggest that high-stable sites pose a risk of Lyme disease exposure to the community as they have reproducing tick populations with consistent levels of B. burgdorferi infection. Continued surveillance for I. scapularis, B. burgdorferi, and range expansion of other tick species and emerging tick-borne pathogens is important to identify areas posing a high risk for human exposure to tick-borne pathogens in the face of ongoing climate change and urban expansion.

Plain language summary

We evaluated the degree of I. scapularis population establishment and Borrelia burgdorferi occurrence in the city of Ottawa, Ontario, Canada from 2017–2019 using active surveillance at 28 sites. Total annual site-specific I. scapularis density ranged from 0 to 16.3 ticks per person-hour. Sites with the highest density were located within the Greenbelt zone, in the suburban/rural areas in the western portion of the city of Ottawa, and along the Ottawa River; the lowest densities occurred at sites in the suburban/urban core. B. burgdorferi infection rates exhibited a similar spatial distribution pattern. Of the 23 sites for which data for two tick cohorts were available, 11 sites were classified as “high-stable”, 4 were classified as “emerging”, 2 were classified as “low-stable”, and 6 were classified as “non-zero”. B. burgdorferi-infected ticks were found at all high-stable sites, and at one emerging site. These findings suggest that high-stable sites pose a risk of Lyme disease exposure to the community as they have reproducing tick populations with consistent levels of B. burgdorferi infection.

Subject

  • Health

Keywords

  • Lyme disease,
  • tick-borne pathogens,
  • Canada,
  • Ixodes scapular,
  • B. burgdorfer

Rights

Peer review

Yes

Identifiers

PubMed ID
33539458
ISSN
1932-6203

Article

Journal title
PLoS ONE
Journal volume
16
Journal issue
2

Citation(s)

Burrows H, Talbot B, McKay R, Slatculescu A, Logan J, Thickstun C, Lindsay LR, Dibernardo A, Koffi JK, Ogden NH, Kulkarni MA. A multi-year assessment of blacklegged tick (Ixodes scapularis) population establishment and Lyme disease risk areas in Ottawa, Canada, 2017-2019. PLoS One. 2021 Feb 4;16(2):e0246484. doi: 10.1371/journal.pone.0246484.

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Communicable diseases

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