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在自然界鼠疫的流行过程中,蚤感染鼠疫是经吸入菌血或败血症期哺乳动物(通常是啮齿动物)的血。鼠疫菌侵入蚤体内只生存于消化道,而不侵犯其它器官。通常细菌不能在前胃和中胃中存活。对鼠疫菌可能是它自身毒力因子的协同保护。因为在吸血蚤胃中最初的消化过程包括了胃蛋白酶和肽酶,以及前胃和中胃的胃刺的机械作用。同时也作用破坏血细胞。这种消化过程也为鼠疫菌进一步的繁殖提供了营养丰富的液体环境及必需的氨基酸。这时PH值中性或偏酸(pH6～7),为鼠疫菌PsaA基因的表达提供了环境条件,也为下一步侵入宿主后抗吞噬作用奠定了基础。
In the natural epidemic of plague, fleas infected with plague are those that have been ingested into the bloodstream of mammals (usually rodents) in the bloodstream of bacteria or septicemia. Yersinia pest invasion of fleas only survive in the digestive tract, without infringing on other organs. Bacteria usually do not survive in the anterior and middle stomachs. Yersinia pestis may be a synergistic protection of its own virulence factors. Because the initial digestion in the Vampire’s flea stomach included pepsin and peptidase, as well as the mechanical action of the stomach spines of the anterior and middle stomachs. At the same time also the role of destroying blood cells. This digestion also provides a nutrient-rich liquid environment and essential amino acids for the further breeding of Y. pestis. At this time PH neutral or partial acid (pH6 ~ 7), provided an environmental condition for the expression of PsaA gene of Y. pestis, which also laid the foundation for the anti-phagocytosis effect after invaded host.