Detections of Babesia odocoilei in Ixodes pacificus and Babesia microti in Ixodes angustus Ticks in British Columbia,Canada

Introduction

Babesiosis is a tick-borne disease impacting humans and animals caused by Babesia spp. parasites. Babesia odocoilei is a protozoan parasite of white-tailed deer and has been associated with mortality events in elk, reindeer, and caribou (Mathieu et al., 2018). B. odocoilei has been documented in both Ixodes scapularis (blacklegged tick) and Ixodes pacificus (western blacklegged tick) (Eshoo et al., 2015; Guillot et al., 2024; Milnes et al., 2019), but there has been only one documented positive tick in British Columbia (BC) from 2019 (Guillot et al., 2024). This article describes the detection of B. odocoilei in four I. pacificus ticks collected through active sampling on a Gulf Island off the coast of Vancouver Island in 2022, expanding the geographical occurrence of B. odocoilei and substantiating I. pacificus as a potential vector of B. odocoilei. This article further describes additional detections of Babesia microti in Ixodes angustus ticks collected in BC.

Materials and Methods

Sentinel regions and site selection

Drag sampling was conducted as part of the Canadian Lyme Sentinel Network, a national surveillance network operated by the Canadian Lyme Disease Research Network (CLyDRN). Regional site selection was conducted as outlined in Guillot et al. (2020). The four sentinel regions in BC that were selected for sampling in 2022 were Central East Vancouver Island, South Vancouver Island and Gulf Islands, Vancouver, and the Okanagan (Fig. 1). Twenty-two sites were sampled once within these regions.

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FIG. 1.

Map of sampling regions where active tick sampling was conducted in British Columbia in 2022 and the location of pathogen detections.

Tick Collection

Tick collection was conducted by dragging a 1 × 1 m piece of white flannel attached to a wooden dowel over the foliage on the side of designated walking trails for a total distance of 2,000 m at each site. The field sampler examined the flannel for ticks approximately every 25 m and collected ticks if present. Sampling occurred between May 9 and July 9, 2022. Temperature and a weather description (e.g., sunny and overcast) at each site were recorded at the time of sampling. Temperatures ranged from 10°C to 25°C with sun or overcast weather reported.

Tick Identification and Laboratory Testing

All captured ticks were sent to Canada’s National Microbiology Laboratory (NML) in Winnipeg, Manitoba, for morphological identification and pathogen testing. In brief, ticks were morphologically identified using Lindquist et al. (2016) as a guide. RNA and DNA were extracted from whole nymphal and adult male individual ticks, while adult females were cut in half longitudinally prior to extraction. A Qiagen RNeasy 96 kit was used to extract both RNA and DNA; ticks were cut up using a sterilized scalpel and mixed with the extraction buffer, following the manufacturer’s instructions. Quantitative PCR was performed for Borrelia species, Anaplasma phagocytophilum, Babesia species, and Powassan virus on the extracted RNA/DNA. Species-specific confirmatory reactions were run to establish tick pathogen positivity status (Supplementary Table S1).

Results and Discussion

A total of 119 ticks were collected in 2022 in BC (I. pacificus: larvae n = 26, nymphs n = 58, adults n = 9; I. angustus: nymphs n = 15, adults n = 2; and Dermacentor andersoni: adults n = 9). Pathogen testing took place on the 84 Ixodes nymphs and adults. B. odocoilei was detected in four Ixodes pacificus nymphs collected from one site on a Gulf Island in the South Vancouver Island sampling region in June 2022. This is the first recorded detection of B. odocoilei since 2019 (Guillot et al. 2020). This site is a park forested with a mixture of Douglas fir and Arbutus menziesii trees and was selected for sampling due to its central location on the island, forest type, and ease of access. In total, 45 ticks (26 larvae, 17 nymphs, and 2 adult males) were collected from this site. The larvae were not identified, but all nymphal and adult ticks were morphologically identified as I. pacificus. All other nymphal and adult I. pacificus ticks collected at this site tested negative for any other pathogens. B. odocoilei has also been detected in ticks collected through passive sampling in BC, and two I. pacificus ticks collected from dogs with no travel outside of the province tested positive for B. odocoilei at the NML in 2019 and 2021, respectively (unpublished data). These passive and active surveillance results substantiate the presence of B. odocoilei in BC and the ability of I. pacificus to carry the pathogen.

I. angustus is a nidicolous tick that feeds on rodents and rarely on humans. It is a known vector of B. microti and was also detected in two I. angustus ticks, a nymph and a female, collected from separate sites in the Vancouver sampling region (Fay and Rausch, 1969). These ticks were both collected from parks sampled in June of 2022. These sites differ from where B. microti was previously detected in 2019 by Guillot et al. (2020), although that site was also sampled, and no additional positive ticks were found.

Babesiosis has not been documented in human or animal populations in BC; however, babesiosis is not a reportable disease in either humans or animals in BC. In Washington State, where babesiosis is a reportable disease, nontravel-related human cases of babesiosis have been reported (Washington State Department of Health, 2024). A One Health approach to the surveillance of ticks and tick-borne diseases that incorporates environmental sampling can provide advanced warning of potential risks to human and animal health prior to the detection of cases.

Conclusion

Continued surveillance and monitoring of ticks and tick-borne pathogens in BC is essential to characterize the abundance and distribution of ticks and the emergence and spread of tick-borne pathogens and to inform risks to human and animal health. The detected presence of Babesia species in ticks collected from surveillance efforts in BC is an important risk signal that requires continued monitoring. This work highlights that vector surveillance through both active and passive strategies provides critical One Health intelligence for risk assessments, prevention and control strategies, diagnostic needs, research priorities, and communication with at-risk populations.

Authors’ Contributions

S.I.: Investigation, project administration, data curation, writing—original draft preparation, and conceptualization. Q.S.: Writing—original draft preparation, conceptualization, visualization, and data curation. H.C.: Investigation, methodology, and writing—reviewing and editing. S.C.: Writing—reviewing and editing and investigation. H.C.: Visualization. M.M.: Investigation and writing—reviewing and editing. E.F.: Writing—reviewing and editing.