High-throughput screening for tick-borne pathogens in Ixodid ticks collected through crowdsourcing in northern Sweden

Ticks are expanding in the northern hemisphere. Along with them, tick-borne pathogens can be introduced into new geographical areas and cause infection and disease in animals and humans. Monitoring the expansion of tick populations is challenging and in large areas such as northern Sweden it can be beneficial to take advantage of citizen science. Therefore, people living in northern Sweden were asked to submit ticks collected from their pets or from themselves during the tick seasons of 2018 (north of river Dalälven; n = 1087) and 2019 (from the four northernmost Swedish provinces; n = 514). Ticks were identified at the species level and further analysed with a microfluidic technique to detect carried tick-borne pathogens. Forty-eight PCR assays targeting an array of tick-borne bacteria, viruses and protozoa were performed per sample in the assay.

The most frequently detected pathogens were Rickettsia helvetica (15.6% in 2018 and 3.5% in 2019) followed by Borrelia garinii (5.9% in 2018 and 11.5% in 2019) and Borrelia afzelii (5.7% in 2018 and 1.2% in 2019).

This study provides data on tick-borne pathogens harbored by feeding ticks collected from a rather poorly investigated geographical area using a One Health perspective. Microfluidic techniques are confirmed to be an effective tool to screen large amounts of samples and to also find pathogens occurring at lower rates. This approach best supports the design of updated risk-maps and to find areas that deserve targeted tick sampling to obtain a more accurate risk assessment and achieve effective disease prevention.