Improvement of Epizootiological Monitoring in the Natural Tularemia Focus of Steppe Type in the Stavropol Territory

The effectiveness of tularemia prevention in humans depends on the timely detection of pathogen cultures in natural foci.

The aim of the study was to increase the efficiency of isolating Francisella tularensis cultures during epizootiological monitoring in natural foci of steppe type through taking into account the dependence of the infection rate of carriers, vectors and environmental objects on the degree of epizootic activity and the survey season.

Materials and methods. An epizootiological survey was conducted in the Stavropol Territory in the period of 2003–2018. A total of 5,692 small mammals, 865 bird pellets and droppings of predatory mammals, 71,387 adult Ixodidae ticks, 94 water samples from local water supplies and 93 field samples from other environmental objects were tested for tularemia.

Results and discussion. F. tularensis cultures were isolated from Ixodidae ticks collected in spring (88.2 %) and summer (12.8 %), from small mammals – mainly in autumn and winter (43.7 % each, respectively), from environmental objects – in winter. All isolates were identified as F. tularensis holarctica, biovar II. During diffuse epizootics in winter in the first quarter of 2017, 23 strains of F. tularensis were isolated. Infection rate among small mammals was 5.7 % of specimens, for water samples from local water supplies – 28.8 %, and for hay and forage samples – 16.6 %. During local epizootics, 31 strains of F. tularensis were isolated. Infection of small mammals was 0.14 %, water samples from local water supplies – 11.9 %, and Ixodidae ticks – 0.024 % of specimens. In the natural steppe tularemia focus, the intensity of epizootics increases in the autumn-winter period, and the most effective way to isolate F. tularensis cultures is to study small mammals and environmental objects. In the spring-summer period, when epizootics do not occur, adult Ixodidae ticks must be studied.

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