Assessing Strategies for the Prevention and Control of Emerging Tick-Borne Diseases in Urban and Peri-Urban Settings

Abstract

Lyme disease (LD) is the most rapidly emerging vector-borne disease in Canada. LD risk is expanding into urban and peri-urban areas due to landscape and climatic changes, along with increasing human use of wildlife habitats. Integrative interventions are needed to maximize the effectiveness of LD prevention and control.

The objective of my thesis was to assess the effectiveness and acceptability of interventions to reduce LD risk in urban and peri-urban settings, using the city of Ottawa as the study site.

I first (1) conducted a systematic literature review and data synthesis of studies on LD prevention and control options comparable to the Canadian context. I then (2) investigated the comparative efficacy of two environmental tick control interventions, by conducting a two-year intervention study in two peri-urban recreational trails in Ottawa. Finally, I (3) assessed the acceptability and feasibility of LD prevention practices used to reduce LD exposure and risk amongst residents of Ottawa using a mixed methods study.

The systematic review summarized effectiveness and utility measures of tick and LD control options. The most common intervention domain in this study was host-targeted interventions, while the synthesis showed that chemical control approaches were the most consistently effective. However, reporting on social acceptability, environmental impact, cost, and feasibility, was inconsistent despite their potential impact on intervention uptake. Field study results found that both treated and untreated woodchips significantly reduced I. scapularis adult and nymphal tick density (incidence rate ratio (IRR) = 0.01, 95 % CI: 0.001-0.08 and IRR = 0.52, 95 % CI: 0.34-0.78) respectively, relative to controls, demonstrating that modifying trailside ecotones with these interventions significantly reduces tick density. The mixed-methods analysis indicated that personal protection strategies and landscape strategies were the most comparably acceptable intervention types in the context of the Ottawa region; furthermore, acceptability was more consistently associated with sociodemographic factors than with risk and exposure variables.

Overall, this thesis evaluated LD prevention options relevant to a Canadian peri-urban context and examined their acceptability and feasibility in Ottawa, generating evidence to inform further development of evidence-based and publicly acceptable LD risk reduction strategies in Canada.