Abstract: From May to September 2024, an investigation of the population density and distribution of the primary plague host and its ectoparasitic vectors, and the plague serological characteristics of marmots was conducted in the Jingtieshan area of the Qilian Mountains, aiming to understand the prevalence of plague among local animals. In May, the marmot densities obtained by the line transect method and the quadrat sampling method were 0.11 individuals/hm2and 0.46 individuals/hm2, respectively. In July, these densities were 0.12 individuals/hm2and 0.58 individuals/hm2, respectively. Through burrow exploration, the burrow flea infestation rates of marmot burrows in May and July were 2.00% and 2.78%, with burrow flea indices of 0.09 and 0.12, while the burrow tick infestation rates of marmot burrow in May and July were 5.33% and 5.56%, with burrow tick indices of 0.06 and 0.08. The flea infestation rate in marmots was 44.32%, and the marmot flea index was 3.80. The tick infestation rate in marmots was 26.70%, and the marmot tick index was 1.15. Through genetic identification and phylogenetic analysis, the parasitic vectors found on the body surface of the marmots includeIxodes crenulatus, Oropsylla silantiewi, Callopsylla dolabris, andCallopsylla sparsilis, and among them,C. dolabriswas predominant, accounting for 94.01% of the total flea population. Serological tests （including colloidal gold and indirect hemagglutination assays） revealed that the positive rate of marmot serum antibodies was 4.55% （8/176）. The average age of these marmots with positive serum antibodies was 3.75 years, and they were mainly detected in May （3 individuals） and July （4 individuals）. High marmot activity was observed along Provincial Highway S215 and within study sites, and the densities of marmots and their surface-dwelling parasites were both high. The positive rate of serum antibodies in marmots and the ages of antibody-positive marmots suggested that an animal plague epidemic may have occurred in this natural plague focus in recent years, indicating a risk of plague transmission among animals in this area, and continuous plague surveillance should be carried out.

Key words: plague;Marmota himalayana, plague focus, density, vector