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The majority of suggested mechanisms of Borrelia spreading inside erythema migrans (EM) are developed from in vitro studies and animal models. This report is the first to describe pathomorphological substrate of EM caused by Borrelia spielmanii in humans, addressing the hypothesis of enhanced Borrelia penetration through extracellular matrix. In the process of ruling out of atypical Masters’ disease, we conducted a punch biopsy of suspected EM and a two-tier serology testing for Lyme borreliosis, where we registered antibodies against B. spielmanii. Skin biopsy showed CD4+and CD8+lymphocyte involvement and high activity of matrix metalloproteinase 9. No alterations were detected in distribution and morphology of collagen type I and IV. Therefore, it is suggested that other mechanisms should be considered as major contributing factors to local spreading of B. spielmanii.

Lyme borreliosis (LB) is the most common tick-borne disease in Serbia and other European countries. Rabies is a fatal zoonosis distributed worldwide and is caused by the rabies virus. Professionals at risk of rabies—including veterinarians, hunters, communal service workers, and forestry workers—overlap with some professions at a higher risk of exposure to tick bites and tick-borne pathogen infections. We hypothesized that individuals identified by the public health system as at risk of rabies virus infection, and consequently vaccinated against rabies virus, also share a higher likelihood of Borrelia exposure. To test our hypothesis, a case-control study was carried out during 2019 in Serbia to determine the seroprevalence of anti-Borrelia antibodies in two case groups (individuals at risk and vaccinated against rabies virus) and a control group (individuals without risk of rabies). Individuals vaccinated against rabies following either “pre-exposure protocol” (PrEP, n = 58) or “post-exposure protocol” (PEP, n = 42) were considered as rabies risk groups and healthy blood donors (n = 30) as the control group. The results showed higher Borrelia seroprevalence in PrEP (17.2%, 10/58) and PEP (19.0%, 8/42) groups compared with the control group (6.67%, 2/30). Furthermore, odds ratio (OR) analysis showed that risk of rabies (in either the PrEP (OR = 2.91) or PEP (OR = 3.29) groups) is associated with increased odds of being seropositive to Borrelia. However, the difference in Borrelia seroprevalence between groups was not statistically significant (Chi-square (χ²) test p &gt, 0.05). The shared odds of LB and rabies exposure found in this study suggest that, in countries where both diseases occur, the common citizen can be at risk of both diseases when in a risky habitat. These findings are important to guide physicians in targeting high-risk groups, and diagnose LB, and to guide decision-makers in targeting control and prevention measures for both infections in risk areas.