STUDY ON TICKS REMOVED FROM PATIENTS FOR INFECTION WITH BORRELIA BURGDORFERI AND THEIR NUMBER DEPENDING ON TEMPERATURE AND PRECIPITATION IN 2016-2021

Abstract

Background: Deacarization, applied epidemiological measures, and climatic factors affect the abundance of ticks. On the other hand, ticks themselves are a factor of great epidemiological and epizootic importance. Studies  concerning the influence of climatic factors on ticks and their infection with B. burgdorferi are still limited in Bulgaria. The aim was to investigate the abundance of ticks in relation to temperature and precipitation, as well as the infection with B. burgdorferi of ticks removed from patients during the period 2016-2021. Materials/methods: A total of 10,907 ticks were collected from patients and classified according to species and stage of development. Nested PCR was performed targeting two sites of the spacer region between 5S and 23S of B. burgdorferi sensu lato rRNA.  Weather data were collected from free Internet meteorological sites. Results: It was found that 92-96% of the ticks belonged to the species Ixodes ricinus. PCR data were obtained for infestation of ticks in 2016-2021. Only in 2018, the highest number of ticks was observed in May, while in the other five years - in June, which was analyzed in relation to the average temperature and precipitation. Conclusion: An increase in tick abundance was observed at average temperatures around 20°C, with rainfall on the days before the peak. During the 6-year period, the highest number of ticks was collected in June 2021, which could be explained with the high average temperatures and abundant precipitations during the preceeding spring months (April – June).