Ecological Mechanisms Underlying the Persistence of Yersinia pestis in the Natural Plague Foci of Kazakhstan: An Integrated Ecological Framework

Plague remains a significant natural-focal infection, yet the mechanisms underlying the long-term persistence of Yersinia pestis during inter-epizootic periods remain incompletely understood. This study integrated published evidence with epizootiological monitoring data from Kazakhstan (1990–2025) and detailed field and laboratory investigations conducted during 2021–2023 to develop an integrated ecological framework of plague persistence. Abiotic and biotic niches, reservoir hosts, flea vectors, and adaptive states of Y. pestis were evaluated according to the strength and type of supporting evidence. Long-term surveillance identified spatially recurrent enzootic cores and documented the continued presence of the great gerbil (Rhombomys opimus)–flea host–vector system across major desert plague territories. Field investigations covered approximately 120,000 km2 and included 4586 environmental and biological samples. Bacteriological examination yielded 24 viable Y. pestis isolates belonging to the Medievalis biovar, whereas real-time PCR detected Y. pestis-specific DNA in 88 of 4586 samples (1.92%), with the highest positivity observed in ectoparasite suspensions (66/868; 7.60%). Laboratory evidence was concentrated in five investigated foci containing recurrent enzootic core areas, while no positive findings were obtained in three comparison foci. These findings support an evidence-weighted ecological framework in which established host–vector transmission operates within spatially structured reservoir populations and heterogeneous environments, while additional environmental and bacterial persistence mechanisms remain plausible but require further experimental validation.