Epidemiological study of Lyme disease in Bulgaria

Abstract

Objectives: Lyme disease (Lyme borreliosis) is a transmissible infection, common in the temperate climate zones. It is caused by a group of spirochetal bacteria known as Borrelia burgdorferi sensu lato complex. The aim of the present work was to investigate the incidence rate of borreliosis in different regions of Bulgaria and to identify possible risk factors for its occurrence.

Methods: National and regional borreliosis incidence rates for 2009-2018 were obtained from the public database of the National Centre of Public Health and Analyses. Their association with some socio-demographic variables and the geographic location (south or north) of the regions was tested with Spearman's correlation analysis and simple linear regression.

Results: The mean annual incidence for the last 10 years (2009-2018) in Bulgaria was 6.9 (range 4.1-11.6) cases per 100,000 inhabitants. We found that the Lyme disease was highly fluctuating at regional level with incidence rates varied from 0.3 to 30.9 per 100,000 inhabitants. Several regions showed significantly higher endemicity for the disease. Socio-demographic factors were not found to be important for Lyme disease frequency while the geographic location in the north part of the country was a significant risk factor for it.

Conclusions: Lyme disease is a serious health risk in Bulgaria especially in its northern part - regions on the north are the most vulnerable to a higher incidence of the disease.

Keywords: Lyme disease; epidemiology; geographic distribution; incidence rates; ticks.