Temporal Detection Limits of Remnant Larval Bloodmeals in Nymphal Ixodes scapularis (Say, Ixodida: Ixodidae) Using Two Next-Generation Sequencing DNA Barcoding Assays.

Using next-generation sequencing DNA barcoding, we aimed to determine: 1) if the larval bloodmeal can be detected in Ixodes scapularis nymphs and 2) the post-moult temporal window for detection of the larval bloodmeal. Subsets of 30 nymphs fed on a domestic rabbit (Oryctolagus cuniculus Linnaeus, Lagomorphia: Leporidae) as larvae were reared and frozen at 11 time points post-moult, up to 150 d. Vertebrate DNA was amplified using novel universal (UP) and species-specific primers (SSP) and sequenced for comparison against cytochrome c oxidase subunit I barcodes to infer host identification. Detectable bloodmeals decreased as time since moult increased for both assays. For the SSP assay, detection of bloodmeals decreased from 96.7% (n = 29/30) in day 0 nymphs to 3.3% (n = 1/30) and 6.7% (n = 2/30) at 4- and 5-mo post-moult, respectively. A shorter temporal detection period was achieved with the UP assay, declining from 16.7% (n = 5/30) in day 0 nymphs to 0/30 in 3-d-old nymphs. Bloodmeal detection was nonexistent for the remaining cohorts, with the exception of 1/30 nymphs at 2-mo post-moult. Host detection was significantly more likely using the SSP assay compared to the UP assay in the first three time cohorts (day 0: χ 2 = 39.1, P < 0.005; day 2: χ 2 = 19.2, P < 0.005; day 3: χ 2 = 23.3, P < 0.005). Regardless of the primer set used, the next-generation sequencing DNA barcoding assay was able to detect host DNA from a larval bloodmeal in the nymphal life stage; however, a short window with a high proportion of detection post-moult was achieved.

Sentinel surveillance of Lyme disease risk in Canada, 2019: Results from the first year of the Canadian Lyme Sentinel Network (CaLSeN).

BACKGROUND: Lyme disease is an emerging vector-borne zoonotic disease of increasing public health importance in Canada. As part of its mandate, the Canadian Lyme Disease Research Network (CLyDRN) launched a pan-Canadian sentinel surveillance initiative, the Canadian Lyme Sentinel Network (CaLSeN), in 2019. OBJECTIVES: To create a standardized, national sentinel surveillance network providing a real-time portrait of the evolving environmental risk of Lyme disease in each province. METHODS: A multicriteria decision analysis (MCDA) approach was used in the selection of sentinel regions. Within each sentinel region, a systematic drag sampling protocol was performed in selected sampling sites. Ticks collected during these active surveillance visits were identified to species, and Ixodes spp. ticks were tested for infection with Borrelia burgdorferi, Borrelia miyamotoi, Anaplasma phagocytophilum, Babesia microti and Powassan virus. RESULTS: In 2019, a total of 567 Ixodes spp. ticks (I. scapularis [n=550]; I. pacificus [n=10]; and I. angustus [n=7]) were collected in seven provinces: British Columbia, Manitoba, Ontario, Québec, New Brunswick, Nova Scotia and Prince Edward Island. The highest mean tick densities (nymphs/100 m2) were found in sentinel regions of Lunenburg (0.45), Montréal (0.43) and Granby (0.38). Overall, the Borrelia burgdorferi prevalence in ticks was 25.2% (0%-45.0%). One I. angustus nymph from British Columbia was positive for Babesia microti, a first for the province. The deer tick lineage of Powassan virus was detected in one adult I. scapularis in Nova Scotia. CONCLUSION: CaLSeN provides the first coordinated national active surveillance initiative for tick-borne disease in Canada. Through multidisciplinary collaborations between experts in each province, the pilot year was successful in establishing a baseline for Lyme disease risk across the country, allowing future trends to be detected and studied.

Assessing the Repeatability of Tick Dragging as a Method for Ixodes scapularis Surveillance.

Tick dragging is an important tool used by public health for Ixodes scapularis surveillance to identify Lyme disease risk areas in Ontario, Canada. Concerns have been raised on the repeatability of tick dragging due to fluctuations that occur in the tick population in response to micro- and macroclimatic variations. Our objective was to assess the repeatability of tick dragging over a short timescale by examining three outcome measures: presence/absence of ticks, tick abundance, and likelihood of tick establishment based on an indicator developed by Clow et al. ( 2018 ). We conducted tick dragging twice per site within a 1-month period at a total of 15 sites in eastern and southern Ontario. Ixodes scapularis were detected at 11 sites. The outcome of presence/absence was consistent at 13 of 15 sites. Abundance was highly variable, changing between each visit at sites where ticks were detected. The likelihood level was consistent at 13 of 15 sites. Based on the kappa statistic, there was substantial agreement between measurements for the presence/absence and the likelihood levels. Our results indicate that both presence/absence and likelihood levels provide more consistent outcomes for tick dragging than tick abundance alone; however, applying the dragging data to the likelihood indicator provides additional information about the potential risk associated with I. scapularis establishment in the area.