Central-Caucasian natural plague focus was permanently epizootically active since its discovering in 1971 till 2007. Inter-epizootic period has been in progress since 2008. It was not possible to isolate agent strains from field material. Therefore a forecast for focus activation is a relevant task, especially against the background of registered plague cases in humans in 2014–2016. Objective of the study was to create a forecasting model for quantitative prediction of possible activation or maintenance of inter-epizootic period. Materials and methods. We used archival data of Kabardino-Balkar Plague Control Station: journals of rodents’ autopsy, annual reports on epizootiological surveillance, meteorological data from meteostation “Kislovodsk” over the period of 1989–2017, and our epidemiological data for the period 2010 to 2017. We applied Spearman nonparametric correlation analysis, regression analysis, including principal component method, quarterly analysis, and inhomogeneous sequential pattern recognition procedures for statistical processing. Results and discussion. We have designed statistical model which provides for forecasting of plague focus epizootic activity proactively, a year in advance and 99 % probability or higher. The model was tested on retrospective data over the course of 7 years. All predictions were correct. The operational forecasts from 2015 to 2017 proved right too. However there is a possibility of fast changes in the ecology system conditions of the Central-Caucasian natural plague focus because of the global warming. Thereby the forecasting model will be annually checked for informative value of the predictors and, if necessary, adjusted accordingly.
Analysis of the long-term data made it possible to identify three periods of epizootic activity of the Central Caucasian high-mountain natural plague focus against the background of the overall downward trend. In the third period (2000-2010) the focus was shown to be under the intense negative influence of natural and anthropogenic factors that stipulated its depression. The natural factors were weather conditions unfavorable for life-sustaining activity of mountain ground-squirrels, the main plague carriers in this focus. Anthropogenic pressure over the focus manifested as follows. The quantity of cattle decreased, that resulted in decrease of territories of the mountain pasturelands, the natural habitats of mountain ground-squirrels. As areas suitable for life-sustaining activity of the mountain ground-squirrel populations reduced, the number of their settlements declined. With account taken for the effect of the anthropogenic influence stated above, short-term and medium-term prognoses of epizootic activity of Central Caucasian high-mountain natural plague focus indicate of rare non-intensive epizooties.
Within the limits of Central Caucasian high-mountain natural plague focus discovered are two zones of natural focality. The first natural focality zone in the mountain steppe of the eastern part of the focus has a parasitic complex similar in structural organization and functioning to lowland foci of the souslik type. Another one, situated in the western part of the focus, is compatible with Tuva mountain natural plague focus, where fleas Neopsylla setosa are absent, and epizootic activity is characterized by a single-humped curve with an apex for July-August period. The similarities stated above can be used for optimization of epidemiological surveillance techniques, preventive measures, and methodology of studying mountain natural plague foci of the souslik type.
В статье приведены сведения о распространении блох горного суслика по территории Центрально-Кавказского высокогорного природного очага чумы. Для иллюстрации различия фаунистических комплексов этих паразитов на всех участках ареала горного суслика, включая высотные пояса, использованы видовые индексы доминирования имаго блох в гнездах хозяев. Фаунистические комплексы блох горного суслика формируются из видов, способных к существованию в климатических условиях конкретного участка ареала хозяина. Имаго основного переносчика возбудителя чумы C. t. elbrusensis доминируют по всей территории очага; распространение дополнительного (N. s. setosa) и случайных переносчиков (F. semura, O.i. ilovaiskii и R. li) различно, лимитируется климатическими условиями.
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