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Study of natural foci of Tularemia in Lviv Oblast, Ukraine

2019; Elsevier BV; Volume: 79; Linguagem: Inglês

10.1016/j.ijid.2018.11.348

1878-3511

Lesja Hatsiy, Oksana Velychko, Lillia Vasiunets, Oksana Semenyshyn,

Insect and Pesticide Research

Purpose: to determine the role of ticks in existence of tularemia natural foci, including expansion of their boundaries and emergence of new enzootic areas. Methods & Materials: During 2013-2017, 34,170 samples of ticks were collected by flagging and dragging; identified and tested using IHA and PCR methods Results: The most permanent focus of tularemia with the tendency of geographical distribution in Lviv Oblast is the Bystrytsia river floodplain near Carpathian region. In samples collected from natural biotopes, I.ricinus was subdominant (43.0%) and D.reticulatus was a dominant species (57.0%). D.reticulatus (76.0%) was also a dominant species in samples collected from cattle. The density index (DI) of D.reticulatus varied from 1.5 to 5.1, and the specific weight (SW) was from 0.6 to 1%. DI of I.ricinus varied from 0.6 to 6.6, and SW was from 0.3 to 0.95%. Analysis of the data demonstrated change of a dominant species. In serological studies, F.tularensis antigen was detected in 8.0% of 34,170 ticks (358 samples), including D.reticulatus (57.0%) and I.ricinus (43.0%). F.tularensis DNA was detected in 4 (6.3%) samples (3 D.reticulatus and one I.ricinus) of 6,340 ticks (64 samples) using PCR. Most of the positive findings were obtained in the known enzootic areas. Positive results were sporadically detected in areas that had not been listed as enzootic, and that requires additional studies. Conclusion: The results of entomological monitoring indicate the preservation of natural foci of tularemia in Lviv Oblast. Vector spread of the pathogen contributed to formation of permanent natural foci of tularemia with an epicenter in the Bystrytsia floodplain in the Carpathian region, where since 1975, 134 cultures of F.tularensis have been isolated from ixodic ticks: 123 from D.reticulatus and 12 from I.ricinus. Based to the results of ticks testing, a new territory that is located far from well-known foci was discovered. The change of the dominant tick species from I.ricinus to D.reticulatus was established.