Current Status of the Sari-Dzhas Natural Focus of Plague, Kyrgyzstan: Epizootic Activity and Marmot Population

Abstract

The Sari-Dzhas natural mountain focus of plague with an area of 5000 sq. km is located mainly in Kyrgyzstan. This enzootic area belongs to a group of Tien-Shan mountain plague foci and crosses the boundaries of Kazakhstan, Kyrgyzstan, and China. After collapse of Soviet Union, this area was not investigated fully, thence we have estimated current status of hosts and vectors comparing to 1977 in the Sari-Dzhas focus. For period 1977-2014, the number of the gray marmot (Marmota baibacina) as main host of plague has decreased twice due to regular chemical suppression of focal area, but now there is a tendency for population recovery. If negative impact of human activity (hunting, livestock, and tourism) will be minimized, the population density should rise in the near future, related to high reproduction score of animals. Significant increase of number of narrow-skulled vole (Microtus gregalis) observed on focus area in 1977-2017 can effort a risk of pathogen transmission in cross-populations of marmots provided by recovery of vector number between different hosts. For whole observation period in the Sari-Dzhas focus were described 33 species of marmot fleas with dominated Oropsylla silantiewi (67% from whole amount of fleas) and Radinopsilla li ventricosa (6.5%). Deep dustation of marmot burrows by 10% dichlorodiphenyltrichloroethane (DDT) conducted in 1980s caused significant decrease of ectoparasite abundance: the number of specific fleas is strongly diminished, while recovery of ticks and lice number is faster. At the same time, Yersinia pestis constantly circulates in the focal area, which is comfortable for interacting of human populations and pathogen hosts. Last plague epizootic was recorded in 1983 and recent outbreaks among gray marmot and its vectors with varying intensity are registered again starting from 2012. Thus, the Sari-Dzhas natural plague focus remains active with all links of plague epizootic cycle (marmot-vector-rodent) and needs strong monitoring every year.

Marmots and Yersinia pestis Strains in Two Plague Endemic Areas of Tien Shan Mountains

“…Apparently, these factors give optimal conditions for the long-term circulation of Y. pestis biovar Antiqua (0.ANT2, 0.ANT3) in the populations of its natural host (31, 37). In total, 462 strains of Y. pestis were registered in the Sari-Dzhas area from 1944 to 1976 (4, 6, 7). Ectoparasites are actively involved in the epizootic process, in particular O. silantiewi and Rh.…”

“…In June–August 2012–2017, the Karakol Anti-Plague Department (KAPD) of the Republic Center for Quarantine and Dangerous Infections (RCQDI) organized field surveys within the Sari-Dzhas and Upper-Naryn foci. The fieldwork was organized as described by Weaver et al (22) and Sariyeva et al (6, 7). All work with wild and laboratory animals and plague strains was conducted in accordance with the regulations and protocols approved by the Ministry of Health of Kyrgyzstan (23) in 2015.…”

“…The Kyrgyz Ministry of Health established a temporal quarantine in parts of the country's mountainous northeast (5), where the risk of plague is well-known for a century. The endemic areas were investigated previously starting from 1942, and the last activity of plague was reported there in 1983 (4, 6, 7).…”

“…The collapse of the Soviet Union and subsequent separation of anti-plague station in Kyrgyzstan from the federal anti-plague system led to dramatic reduction of plague investigations and plague control measures. During the last couple of decades, the density of marmots was significantly reduced as a result of chemical suppression in the 1960s, increased hunting of marmots, habitat destruction, and climate changes (6–8, 21). This raises the question whether the changes in rodent communities in these areas affected marmots playing a leading role in circulation of plague pathogen.…”

iMarmot: an integrative platform for comparative and functional genomics of marmots

“…An international marmot network of scientists and managers has been established to work on the conservation issues of these species since 2008 (http://www.cons-dev.org/ marm/MARM/EMARM/framarm/framarm.html). Meanwhile, plagues prevalence in some marmots were frequently reported to co-occur with sporadic epidemic in people all over the world, which also give rise to special supervision to the population fluctuations and epizootic activity of marmots [6][7][8]. Therefore, not only sociobiologists, conservationists and epidemiologist pay high attention to marmots, but also physiologists, who consider marmots as excellent animal models for the research of hibernation mechanism with possible applications to human medicine [4,9].…”