Abundance of ticks and tick-borne pathogens in domestic gardens in Belgium, 2020-2022: a citizen science approach.

BACKGROUND

Ticks, particularly Ixodes ricinus, are primary vectors for tick-borne diseases in Europe, with private gardens representing an understudied but potentially significant risk habitat. Through a citizen science initiative, we aimed to investigate tick density and pathogen prevalence in domestic gardens across Flanders, Belgium.

METHODS

A total of 185 citizen scientists participated in standardized tick dragging and collecting garden data over multiple occasions from 2020 to 2022. Generalized linear mixed effects models were used to analyze tick density and pathogen prevalence.

RESULTS

Ticks were detected in 44.3% of 185 gardens. They were most frequently found in rural gardens (60.2% of rural gardens, 50/83), but also in suburban (28.9%, 11/38) and urban gardens (50.0%, 4/8). Ixodes ricinus was the dominant species (94.7% out of 1162 ticks), with all life stages present. Additionally, few individuals of Ixodes frontalis (5.0%) and Ixodes hexagonus (0.3%) were collected. Ticks were found in a variety of vegetation types, however the highest proportions of successful collections were in fallen leaves (47.4%) and fallow land (46.2%). Nymphal density was positively associated with the number of mammal species observed and an association with vegetation type was found: significantly more nymphs were collected on wild vegetation (with fallow land) and fallen leaves, compared to mown grass, tall grass and flower beds (with vegetable gardens). Pathogen screening revealed that 34.1% of ticks carried at least one pathogen, with Borrelia burgdorferi s.l. most prevalent (19.6%), followed by Rickettsia spp. (11.7%). Co-infections were observed in 6.6% of ticks. Borrelia burgdorferi s.l. prevalence was significantly lower in the presence of dogs and increased with nymphal density. Additionally, a significant interaction was found between life stage and the number of bird species.

CONCLUSIONS

The presence of Ixodes ricinus in gardens, coupled with the detection of pathogens at prevalence levels similar to those in natural habitats, suggests that private gardens may serve as overlooked risk areas for tick exposure. This underscores that raising public awareness, combined with effective garden management strategies, may help mitigate the risk of infection with tick-borne diseases. Future research could focus on evaluating the effectiveness of prevention and garden management measures.