Pasteurella multocida strains of a novel capsular serotype and lethal to Marmota himalayana on Qinghai-Tibet plateau in China

Pasteurella multocida is a zoonotic pathogen causing serious diseases in humans and animals. Here, we report P. multocida from wildlife on China's Qinghai-Tibet plateau with a novel capsular serotype, forming a single branch on the core-genome phylogenetic tree: four strains isolated from dead Himalayan marmot (Marmota himalayana) and one genome assembled from metagenomic sequencing of a dead Woolly hare (Lepus oiostolus). Four of the strains were identified as subspecies multocida and one was septica. The mouse model showed that the challenge strain killed mice within 24 h at an infectious dose of less than 300 bacteria. The short disease course is comparable to septicemic plague: the host has died before more severe pathological changes could take place. Though pathological changes were relatively mild, cytokine storm was obvious with a significant rise of IL-12p70, IL-6, TNF-αand IL-10 (P < 0.05). Our findings suggested P. multocida is a lethal pathogen for wildlife on Qinghai-Tibet plateau, in addition to Yersinia pestis. Individuals residing within the M. himalayana plague focus are at risk for P. multocida infection, and public health warnings are necessitated.