Linking human tick bite risk with tick abundance in the environment: A novel approach to quantify tick bite risk using orienteers in Scotland

Ribeiro, R, Eze, JI*, Gilbert, L*, Macrae, A, Duncan, A, Baughan, J, Gunn*, G & Auty, H* 15 December 2022

Highlights
• We used a novel approach to estimate tick bite rate. This approach accounts for activities where tick bites did and did not occur, time of exposure and tracking of participants.

• The number of tick bites reported per person is better explained by the duration of exposure (hours) than by the distance covered.

• Tick abundance in the environment and tick bite rate are strongly correlated; data from questing tick surveys are a useful proxy for the risk of human tick bites.

• Orienteers have a high rate of tick bites. Tick bite rate is higher in orienteers that ran earlier in the day, exposed to higher temperatures and in woodland habitats.

Abstract
The rate that people are bitten by ticks is critical in determining the risk of tick-borne infections but is rarely quantified accurately. Often tick abundance in the environment is used as a proxy for tick bite risk, but the relationship with risk is poorly understood. We used a novel citizen science approach to measure tick bite rate in orienteers, to assess the relationship between tick abundance and tick bite risk and to identify risk factors for tick bites. Eleven orienteering events were attended in Scotland between August 2018 and September 2019. The number of tick bites in orienteers, and the time and distance of activity were collected using an online questionnaire. Tick abundance in the same areas used for the orienteering events was estimated by surveying ticks on ground vegetation using blanket drags. Among orienteers, mean incidence was 409 tick bites per 1,000 person-hours. Tick abundance and tick bite rate were strongly correlated, indicating that data from questing tick surveys is a useful proxy for the risk of human tick bites. Tick bite rate was better explained by the activity duration than distance covered and was higher in orienteers that ran earlier in the day, exposed to higher temperatures and in woodland habitats. This study highlights the value of the citizen science approach used, which crucially included submission of activity reports both with and without ticks, to generate robust data on tick bite rate. Accurately measuring tick bite rate and understanding environmental factors that influence it are essential in mitigating the risk of tick-borne diseases.

 

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