Plaguebearing

Plaguebearing refers to the role of living organisms, primarily rodents and their ectoparasites like fleas, in carrying and transmitting the bacterium *Yersinia pestis*, the causative agent of plague. This enzootic cycle, where the bacterium circulates within animal populations, is crucial for the persistence of plague in nature. Rodents such as rats, mice, squirrels, and prairie dogs are common reservoirs for *Yersinia pestis*.

When an infected flea bites a susceptible rodent, it ingests the bacteria. The bacteria multiply in the flea's gut, eventually blocking its proventriculus, a part of its digestive system. When this blocked flea attempts to feed on another host, it regurgitates the infected blood meal into the new host, thus transmitting the plague. If the new host is also a rodent, the enzootic cycle continues.

However, plague can spill over from these rodent reservoirs to other animals, including humans. This typically occurs when humans come into close contact with infected rodents or their fleas, often through bites or inhalation of infectious droplets from aerosolized bacteria in the environment. The primary vector for human transmission has historically been the Oriental rat flea (*Xenopsylla cheopis*), although other flea species can also transmit the disease. Understanding plaguebearing is essential for public health efforts to prevent and control plague outbreaks.