Laboratory of Bacteriology, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, Montana, United States of America.
Rocky Mountain Veterinary Branch, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, NIH, Hamilton, Montana, United States of America.
PLoS Biol. 2024 May 21;22(5):e3002625. doi: 10.1371/journal.pbio.3002625. eCollection 2024 May.
Yersinia pestis, the causative agent of plague, is a highly lethal vector-borne pathogen responsible for killing large portions of Europe's population during the Black Death of the Middle Ages. In the wild, Y. pestis cycles between fleas and rodents; occasionally spilling over into humans bitten by infectious fleas. For this reason, fleas and the rats harboring them have been considered the main epidemiological drivers of previous plague pandemics. Human ectoparasites, such as the body louse (Pediculus humanus humanus), have largely been discounted due to their reputation as inefficient vectors of plague bacilli. Using a membrane-feeder adapted strain of body lice, we show that the digestive tract of some body lice become chronically infected with Y. pestis at bacteremia as low as 1 × 105 CFU/ml, and these lice routinely defecate Y. pestis. At higher bacteremia (≥1 × 107 CFU/ml), a subset of the lice develop an infection within the Pawlowsky glands (PGs), a pair of putative accessory salivary glands in the louse head. Lice that developed PG infection transmitted Y. pestis more consistently than those with bacteria only in the digestive tract. These glands are thought to secrete lubricant onto the mouthparts, and we hypothesize that when infected, their secretions contaminate the mouthparts prior to feeding, resulting in bite-based transmission of Y. pestis. The body louse's high level of susceptibility to infection by gram-negative bacteria and their potential to transmit plague bacilli by multiple mechanisms supports the hypothesis that they may have played a role in previous human plague pandemics and local outbreaks.
鼠疫耶尔森菌是鼠疫的病原体，是一种高度致命的媒介传播病原体，在中世纪的黑死病期间导致欧洲大量人口死亡。在自然界中，鼠疫耶尔森菌在跳蚤和啮齿动物之间循环；偶尔会溢出到被感染跳蚤叮咬的人类身上。因此，跳蚤和携带它们的老鼠被认为是以前鼠疫大流行的主要流行病学驱动因素。人体寄生虫，如体虱（Pediculus humanus humanus），由于其作为鼠疫杆菌低效传播媒介的声誉而在很大程度上被忽视。使用适应膜饲养的体虱株，我们表明，在菌血症低至 1×105 CFU/ml 时，一些体虱的消化道会慢性感染鼠疫耶尔森菌，并且这些虱子经常排出鼠疫耶尔森菌。在更高的菌血症（≥1×107 CFU/ml）下，一部分虱子会在 Pawlowsky 腺（PGs）中感染，PGs 是虱子头部的一对假定的辅助唾液腺。与仅在消化道中感染细菌的虱子相比，感染 PG 的虱子更一致地传播鼠疫耶尔森菌。这些腺体被认为会分泌润滑剂到口器上，我们假设当它们受到感染时，它们的分泌物在叮咬前污染口器，导致基于叮咬的鼠疫耶尔森菌传播。体虱对革兰氏阴性菌的高度易感性及其通过多种机制传播鼠疫杆菌的潜力支持了这样一种假设，即它们可能在以前的人类鼠疫大流行和局部暴发中发挥了作用。
