Plague Outbreak of a <i>Marmota himalayana</i> Family Emerging from Hibernation

Abstract

In April 2021, a plague outbreak was identified within one <i>Marmota himalayana</i> family shortly after emerging from hibernation, during plague surveillance in the <i>M. himalayana</i> plague foci of the Qinghai-Tibet Plateau. A total of five marmots were found dead of <i>Yersinia pestis</i> near the same burrow; one live marmot was positive of <i>Y. pestis</i> fraction 1 (F1) antibody. Comparative genome analysis shows that few single nucleotide polymorphisms were detected among the nine strains, indicating the same origin of the outbreak. The survived marmot shows a high titer of F1 antibody, higher than the mean titer of all marmots during the 2021 monitoring period (<i>W</i> = 391.00, <i>Z</i> = 2.81, <i>p</i> < 0.01). Marmots live with <i>Y. pestis</i> during hibernation when the pathogen is inhibited by hypothermia. But they wake up during or just after hibernation with body temperature rising to 37°C, when <i>Y. pestis</i> goes through optimal growth temperature, increases virulence, and causes death in marmots. A previous report has shown human plague cases caused by excavating marmots during winter; combined, this study shows the high risk of hibernation marmot carrying <i>Y. pestis</i>. This analysis provides new insights into the transmission of the highly virulent <i>Y. pestis</i> in <i>M. himalayana</i> plague foci and drives further effort upon plague control during hibernation.