A computer model of plague epizootic process in the great gerbil (Rhombomys opimus) settlements: Description and test for adequacy

Abstract

The spread of plague epizootics in areas with natural plague foci, including Rhombomys opimus settlements, is usually studied in the course of annual epizootiological observations. Direct studies on the structure of epizootics and parameters of their spread are labor-intensive and, therefore, rare. Nevertheless, a number of authors have performed such studies using different methods, which made it possible to accumulate a certain factual material. This material has provided a basis for a computer model of the epizootic process in R. opimus settlements with interactively adjustable parameters. Mathematically, the model is based on a probabilistic cellular automation. The model conceptually deals with the same types of settlements as in nature: settlements with acute development of the disease, settlements with a certain proportion of immune individuals among rodents, and those not affected by an epizootic and representing a reserve for its further development. The groups of colonies (microfoci) separated from each other and unevenly distributed in the working space of the model are clearly distinguished. The epizootic process in the working space of the model shows more or less ordered cyclic fluctuations, which resemble the curve of epizootic activity in nature, and advances at a rate of 150 m to 1.5 km per 1.7–2.7 months, which well agrees with parameters recorded in field experiments with isotope-tagged animals and in the course of direct observations on the epizootic process in nature Thus, the main characteristics of the model epizootic process are quantitatively and qualitatively close to its natural analogue, which is evidence that the proposed model is conceptually correct and adequate.