# Lacerta agilis and Zootoca vivipara Lizards Infested with Ixodes ricinus Ticks Preferentially Maintain the Circulation of Borrelia lusitaniae and B. burgdorferi Sensu Stricto in Poland

## TL;DR

This study shows that certain lizards in Poland can host ticks that carry Lyme disease bacteria, potentially spreading the infection to humans.

## Contribution

The study is the first to suggest that two lizard species may act as reservoir hosts for B. burgdorferi sensu stricto, a human pathogen.

## Key findings

- Sand lizards (Lacerta agilis) are confirmed as competent reservoirs for B. lusitaniae.
- Both sand lizards and common lizards may serve as reservoir hosts for B. burgdorferi sensu stricto.
- B. lusitaniae was most prevalent in ticks from sand lizards, while B. burgdorferi s.s. dominated in ticks from common lizards.

## Abstract

In Central Europe, lizards are frequent hosts for immature stages of the Ixodes ricinus tick, the principal vector of Lyme borreliosis (LB). This is the most common tick-borne disease and is caused by several species of bacteria from the Borrelia burgdorferi sensu lato (s.l.) complex. Of the 14 genospecies identified in I. ricinus, three account for the majority of LB cases in Europe: B. afzelii, B. garinii and B. burgdorferi sensu stricto. Each of these human-pathogenic species is associated with a particular vertebrate group acting as its natural reservoir. Borrelia afzelii depends on rodents, B. garinii depends on birds, whereas B. burgdorferi s.s. can use both birds and rodents. Certain lizard species are proven reservoir hosts of B. lusitaniae, which is implicated as a potential pathogen in humans. This study aimed to evaluate the prevalence of B. burgdorferi s.l. in sand lizards and common lizards, as well as in their I. ricinus ticks, in suburban areas of western Poland. Our results confirmed that the sand lizard but not the common lizard, can act as a competent reservoir for B. lusitaniae. Furthermore, we suggest for the first time that these two lizard species could be another group of reservoir hosts for the human pathogen B. burgdorferi s.s., alongside birds and rodents.

This study was conducted to assess the involvement of two lizard species: the sand lizard (Lacerta agilis) and the common lizard (Zootoca vivipara), and their Ixodes ricinus ticks, in the circulation spirochetes of the Borrelia burgdorferi s.l. complex. Lizards were captured at three study sites in suburban areas of western Poland. Common lizards were less abundant and occurred only at one site. A total of 1129 ticks were collected from 167 sand lizards and 164 individuals from 42 common lizards. Biopsies of the distal part of the lizard tail were taken from 172 animals. All samples that tested positive by real-time PCR underwent subsequent nested PCR targeting the flaB gene, followed by sequencing. At least 6.3% of I. ricinus ticks (MIR) from L. agilis, and 6.1% from Z. vivipara, were infected. Borrelia lusitaniae was the most prevalent genospecies in L. agilis-derived ticks, accounting for 73.2% of all infected samples, followed by B. burgdorferi s.s. (23.0%). Conversely, this latter species prevailed (90%) over B. lusitaniae (10%) in tick samples from Z. vivipara. Therefore, we believe that sand lizards are competent reservoir hosts for B. lusitaniae, while the role of Z. vivipara for this species is unclear. The high prevalence of B. burgdorferi s.s. was also found in infected larval samples (40.7%) and biopsies (60%) of L. agilis. Thus, in our opinion, these two lizard species could be another group of reservoir hosts for this human pathogen, along with birds and rodents.