Background The risk of developing Lyme borreliosis (LB) following a tick bite is influenced by several independent factors, including the promptness of tick removal, host immune response, and regional variability in pathogen prevalence. This study employed a citizen science approach to investigate the incidence of LB following Ixodes ricinus bites in Poland and to assess the relationship between Borrelia spirochete load, tick attachment duration, and subsequent LB development in humans. Methods The study was conducted over 2 years (2021–2022). Participants were instructed to submit removed ticks and to complete questionnaires at enrollment and 8 weeks post-bite. All LB cases were physician-confirmed on the basis of national clinical criteria. Tick attachment duration was estimated using scutal and coxal indices. Genomic DNA extracted from ticks was subjected to molecular screening for Borrelia spp., and spirochete load was quantified using droplet digital polymerase chain reaction (PCR). Results The prevalence of Borrelia infection in I. ricinus ticks was 15.7% (n = 2079). The overall risk of developing LB following a tick bite was 3.1% (n = 1757). Among confirmed LB cases (n = 54), erythema migrans was reported in 64.9%. In cases involving Borrelia-positive ticks (n = 250), the risk of LB increased with attachment duration—from 10.0% for ticks removed within 24 h to 30.0% for those removed after 48 h. Among Borrelia-infected ticks removed from the skin of the patients with LB, Borrelia afzelii was the most frequently detected species, however co-infection with Borrelia miyamotoi was also observed. Notably, both Borrelia prevalence and spirochete load in ticks decreased significantly with prolonged attachment duration. Conclusions The overall risk of LB following an I. ricinus bite was relatively low. While B. afzelii was the dominant species detected, the potential risk posed by B. miyamotoi warrants attention, given its significantly higher spirochete load compared with the B. burgdorferi sensu lato complex, potentially indicating greater transmission efficiency. The observed decline in spirochete load with increasing attachment time suggests a complex dynamic that may influence transmission risk, meriting further investigation. This study highlights the utility of citizen science as a viable method for collecting large-scale data on human–tick encounters, despite methodological constraints inherent in volunteer-based research. Graphical Abstract

Incidence of Lyme borreliosis following Ixodes ricinus tick bites in Poland: a citizen science approach

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2025年11月28日

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Julia Koczwarska,
Agnieszka Pawełczyk,
Renata Welc-Falęciak

摘要

Background

The risk of developing Lyme borreliosis (LB) following a tick bite is influenced by several independent factors, including the promptness of tick removal, host immune response, and regional variability in pathogen prevalence. This study employed a citizen science approach to investigate the incidence of LB following Ixodes ricinus bites in Poland and to assess the relationship between Borrelia spirochete load, tick attachment duration, and subsequent LB development in humans.

Methods

The study was conducted over 2 years (2021–2022). Participants were instructed to submit removed ticks and to complete questionnaires at enrollment and 8 weeks post-bite. All LB cases were physician-confirmed on the basis of national clinical criteria. Tick attachment duration was estimated using scutal and coxal indices. Genomic DNA extracted from ticks was subjected to molecular screening for Borrelia spp., and spirochete load was quantified using droplet digital polymerase chain reaction (PCR).

Results

The prevalence of Borrelia infection in I. ricinus ticks was 15.7% (n = 2079). The overall risk of developing LB following a tick bite was 3.1% (n = 1757). Among confirmed LB cases (n = 54), erythema migrans was reported in 64.9%. In cases involving Borrelia-positive ticks (n = 250), the risk of LB increased with attachment duration—from 10.0% for ticks removed within 24 h to 30.0% for those removed after 48 h. Among Borrelia-infected ticks removed from the skin of the patients with LB, Borrelia afzelii was the most frequently detected species, however co-infection with Borrelia miyamotoi was also observed. Notably, both Borrelia prevalence and spirochete load in ticks decreased significantly with prolonged attachment duration.

Conclusions

The overall risk of LB following an I. ricinus bite was relatively low. While B. afzelii was the dominant species detected, the potential risk posed by B. miyamotoi warrants attention, given its significantly higher spirochete load compared with the B. burgdorferi sensu lato complex, potentially indicating greater transmission efficiency. The observed decline in spirochete load with increasing attachment time suggests a complex dynamic that may influence transmission risk, meriting further investigation. This study highlights the utility of citizen science as a viable method for collecting large-scale data on human–tick encounters, despite methodological constraints inherent in volunteer-based research.

Graphical Abstract