HUMAN LEPTOSPIROSIS IN BULGARIA
EPIDEMIOLOGICAL ANALYSIS OF THE INFECTION, 2014-2023
DOI:
https://doi.org/10.58395/2s2yh357Keywords:
Leptospirosis, serogroups, PCRAbstract
Background: Leptospirosis is a zooanthroponosis with natural outbreaks, of great significance for public health worldwide. According to data from the latest ECDC report, there are 765 confirmed cases of leptospirosis in Europe. Human cases of leptospirosis in Bulgaria have been reported since 1952. A trend towards a decrease in the number of registered cases of leptospirosis in our country has been observed in the last two decades. This study was focused on the analysis of circulating serovars of the genus Leptospira and their distribution, and epidemiological characteristics of laboratory confirmed cases of human leptospirosis for a tеn-year period (2014-2023). It was interesting to reveal the relationship between clinical symptoms, transmission mode and sources of infection, and to assess the status of the problem in our country.
Material and methods: A total of 1152 samples suspected of leptospirosis collected from all regions of the country, were tested by MAT analysis. Of them, paired blood samples (at the beginning of the infection and during the convalescent phase) were taken from 62 patients and were examined by PCR (nested and real time). Suspensions of live serovars from 9 different Leptospira serogroups known to circulate in Bulgaria were used as antigens.
Results: Average annual incidence of the disease was 0.16/100,000 population. The overall case fatality rate was 4.3 % in this period. Analysis of case distribution according to sex showed a high predominance of male patients -75/93 (80.65%), from the age group 50-59 years. Serogroup Icterohaemorrhagiae had the leading aetiological role in 2015-2023, but in 2014 Sejroe was the most commonly detected serogroup. The highest incidence was observed in the district of Sofia city, and far fewer cases were registered in Shumen, Montana, Bourgas and Pleven. The monthly distribution of leptospirosis cases showed that most of the cases appeared in summer and fall with a peak incidence in late summer and early autumn. Analysis of the possible mode of transmission showed that the infection was acquired mainly through occupational exposure (70.67% of cases), mostly livestock farming. Rats were the main risk factor to contract leptospirosis during this period (38.67% of cases). Data analysis showed that 44.08% of the patients suffered from severe disease (Weil’s disease). Acute renal failure, diagnosed in 36.56% , was the main cause for fatality, which was noted also in the previous studies. Anicteric cases (55.91%) had a milder course, in most cases shown to occur as a self-limiting flu-like infection.
Conclusions: The results from this ten-year period show that leptospirosis in Bulgaria is an infection with limited distribution, but the risk of leptospirosis should not be underestimated. The development of real-time PCR method for rapid diagnosis of leptospirosis is very important for the diagnosis of individual cases or during outbreak situations.
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Copyright (c) 2025 Chief Assistant Evgeniya Taseva, Professor Iva Christova, Assoc. Prof. Iva Trifonova, Chief Assistant Teodora Gladnishka, Chief Assistant Elitsa Panajotova, Kim Ngoc, Vladislava Ivanova, Iva Vladimirova, Lilly Marinova (Author)
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