The Altun Mountains are among the most active regions of Marmota himalayana plague foci of the Qinghai-Tibet Plateau where animal plague is prevalent, whereas only three human cases have been found since 1960. Animal husbandry is the main income for the local economy; brucellosis appears sometimes in animals and less often in humans. In this study, a retrospective investigation of plague and brucellosis seroprevalence among humans and animals was conducted to improve prevention and control measures for the two diseases. Animal and human sera were collected for routine surveillance from 2018 to 2021 and screened for plague and brucellosis. Yersinia pestis F1 antibody was preliminarily screened by the colloidal gold method at the monitoring site to identify previous infections with positive serology. Previous plague infection was found in 3.2% (14/432) of the studied human population having close contact with livestock, which indicates evidence of exposure to the Yersinia antigen (dead or live pathogenic materials) in the Altun Mountains. Seroprevalence of brucellosis was higher in camels (6.2%) and sheepdogs (1.8%) than in other livestock such as cattle and sheep, suggesting a possible transmission route from secondary host animals to humans.
Yunnan is the origin of the third plague pandemic. The analysis of human and animal plague characteristics of plague foci in Yunnan enlightens the prevention and control of the next plague pandemics.
Brucellosis is a common zoonotic disease. For this study, the residents of Akesai Kazak Autonomous County, located in the high altitude of the Altun Mountains region of Gansu Province, were selected. These people rely on traditional animal husbandry for their main income. The prevalence of brucellosis and the change of antibody titer in this high-risk population were analyzed, and information on the epidemic in animals in the county was obtained from data records. One hundred ninety-nine persons were screened and 240 serum samples were collected. Eight persons and 27 serum samples were positive based on the rose bengal plate test, and seven persons were confirmed positive by standard agglutination test; 16,000 sheep were tested, of which 130 from nine different households were serum antibody positive. The results indicate that brucellosis seroprevalence increased among sheep and high-risk populations, and the occurrence of cases corresponded to the epidemic among animals. The incidence of human brucellosis was closely related to occupation, and the cases were mainly distributed among herdsmen and butchers. Most cases were asymptomatic or mild, and the serum antibody titers showed a high initial titer but a rapid decline in young cases, whereas those in older cases were relatively low but showed a slow decline.
Plague is a typical natural focus disease that circulates in different ecology of vectors and reservoir hosts. We conducted genomic population and phylogenetic analyses of the Yersinia pestis collected from the 12 natural plague foci in China with more than 20 kinds of hosts and vectors. Different ecological landscapes with specific hosts, vectors, and habitat which shape various niches for Y. pestis. The phylogeographic diversity of Y. pestis in different kinds plague foci in China showed host niches adaptation. Most natural plague foci strains are region‐and focus‐specific, with one predominant subpopulation; but the isolates from the Qinghai–Tibet plateau harbor a higher genetic diversity than other foci. The Y. pestis from Marmota himalayana plague foci are defined as the ancestors of different populations at the root of the evolutionary tree, suggesting several different evolutionary paths to other foci. It has the largest pan‐genome and widest SNP distances with most accessory genes enriched in mobilome functions (prophages, transposons). Geological barriers play an important role in the maintenance of local Y. pestis species and block the introduction of non‐native strains. This study provides new insights into the control of plague outbreaks and epidemics, deepened the understanding of the evolutionary history of MHPF (M. himalayana plague focus) in China. The population structure and identify clades among different natural foci of China renewed the space cognition of the plague.
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