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Background/Aim. The first case of human Lyme borreliosis (LB) in Serbia was recorded in 1987. The number of reported LB cases has increased in the past decade. The aim of this study was to estimate the density of Ixodes ricinus (I. ricinus) ticks, the prevalence of Borrelia burgdorferi sensu lato (B. burgdorferi) in them, and entomological risk index (ERI) at 19 Belgrade localities which were grouped into three categories (forests, park-forests, parks). The values of ERI were compared with the number of tick bites in humans. Methods. Ticks were collected monthly by using the flag hours method and the infection rate was determined by using dark field microscopy. The ERI value was calculated for each locality where the ticks were collected. The related data about tick bites was obtained from the patient protocol of the Institute of Epidemiology, Military Medical Academy, Belgrade. Results. The total number of collected ticks, the number of nymphs and the infection rates of the nymphs were significantly higher in forests (p < 0.05) than park-forests and parks. Statistically, the ERI value was significantly higher in forests than parks of Belgrade (2 = 7.78, p < 0.01). In March and July, the ERI value was also significantly higher in forests, than park-forests (p < 0.01) and parks (p < 0.01). May was the month with the highest ERI value in each ecological category (forests p < 0.05; park-forests p < 0.01; parks p < 0.001). However, the number of tick bites in humans did not correlate with ERI values. Conclusion. The obtained results indicate that the risk of tick bite and human exposure to B. burgdorferi sensu lato is present at all selected localities in Belgrade. For a more comprehensive Lyme disease risk assessment the method of entomological risk index assessment should be combined with other methods, taking into consideration all tick stages and the behaviour and habits of people who may get infected B. burgdorferi sensu lato. [ABSTRACT FROM AUTHOR]

Background/Aim. Factors determining the risk of Lyme disease (LD) may be followed in terms of the type of habitat. The evaluation of the risk of Borrelia burgdorferi (B. burgdorferi) transmission in humans on Ixodes ricinus (I. ricinus) tick habitats is done by means of the ecological risk index, which determines the tick habitat, abundance and infection rate. The aim of this paper was to determine the value of ecological risk index (potential and actual risk – PR and AR) on green areas in 9 pаrks in Belgrade and establish the correlation of this index with tick bites in humans. Methods. Ticks were collected in parks by means of the flag hour method and examined for the presence of LD cause in dark-field microscopic analysis. Point values were assigned to certain parameters and potential and actual risk index evaluated for each habitat. The data on tick bites from the surveyed habitats were obtained from the Protocol of patients bitten by ticks of the Sector for Preventive Medicine, Institute of Epidemiology, Military Medical Academy in Belgrade. Analysis of variance (ANOVA), Tukey test and Pearson's coefficient were used in statistical analysis of data. Results. In Belgrade´s park habitats a high PR of B. burgdorferi transmission was determined, while AR for 4 habitats was categorised as PR, and limited for other 5 habitats. Statistically, in terms of AR values the following habitats were significantly different (p < 0.05): Hаjd Pаrk and Tаšmаjdаn; Hаjd Pаrk and Kаlemegdаn; Hаjd Pаrk and Pionirski Pаrk; Hаjd Pаrk and Bаnovo Brdo; Topčider and Tаšmаjdаn; Topčider and Kаlemegdаn; Topčider and Pionirski Pаrk; Topčider and Bаnovo Brdo Park. A statistically significant correlation (p < 0.05) between bites of adults and the number of bites of infected adults with the AR value was established. Conclusion. In parks of Belgrade, there is a limited AR of B. burgdorferi transmission on the average. The AR values vary from limited to the potential, depending on the ecological features of habitat, the number of collected ticks and their infection rate. In view of the correlation of AR with the bites in humans, this index is significant for assessing LD risk. [ABSTRACT FROM AUTHOR]