Abstract
In Europe, Lyme neuroborreliosis (LNB) is the most severe manifestation of Lyme borreliosis and has recently been added to the communicable disease surveillance list for EU/EEA by the European Commission. In Northern Europe, LNB is primarily caused by the spirochete Borrelia garinii and transmitted by the tick Ixodes ricinus. This Danish observational epidemiologic case-control study includes every identified LNB patient (n = 401) on Funen, Denmark, from 1995-2014. We display spatial and temporal LNB incidence variation, seasonal distribution of cases and local spatial case clustering. Seasonal patterns show LNB symptom-onset peaking in July and a significant seasonal difference in number of cases (p < 0.01). We found no significant change in seasonality patterns over time when dividing the study period into 5-year intervals. We identified a significant local geographical hot-spot of cases with a relative risk of 2.44 (p = 0.013). Analysis revealed a significantly shorter distance to nearest forest for cases compared with controls (p < 0.001). We present a novel map of the focal geographical distribution of LNB cases in a high endemic borreliosis area. Continued studies of case clustering in the epidemiology of LNB are of key importance in guiding intervention strategies.
Highlights
Lyme Borreliosis (LB) is the most common tick-borne infection in Denmark and in Europe[1,2,3]
Humans living in regions with competent hosts of I. ricinus are at higher risk of disease, as these may serve as reservoirs hosts for various pathogens that can be transmitted by tick bites to humans[8]
A regression analysis found that the odds of being a case rather than a control increased with approximately 8% (Odds ratio 1.08) when moving one km closer to a forest (p < 0.001) (Fig. 6, Table 1). In this large retrospective study of a well-defined case population of Lyme neuroborreliosis (LNB), we aimed to examine the temporal changes in LNB incidence
Summary
Lyme Borreliosis (LB) is the most common tick-borne infection in Denmark and in Europe[1,2,3] It is a spirochetal infection caused by Borrelia burgdorferi sensu lato (sl), which in Denmark is transmitted by the tick Ixodes ricinus[2]. This tick species is found throughout the country, but it is most abundant in the eastern and central parts of Denmark[1]. The primary objectives of this observational study were to (1) describe both the spatial and temporal LNB incidence variation, and examine any change in seasonal distribution over the last 20 years, and (2) identify potential spatial patterns of LNB-cases on Funen, and quantify difference in distance to nearest forest between cases and controls based on home addresses
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