How do rats get plague? - briefly
Rats acquire plague mainly through bites from infected fleas that have previously fed on other infected rodents, transmitting the bacterium Yersinia pestis. Direct contact with contaminated carcasses or inhalation of aerosolized bacteria can also cause infection.
How do rats get plague? - in detail
Rats acquire plague when they become infected with the bacterium Yersinia pestis, which circulates in wild rodent populations and is transmitted primarily through arthropod vectors. The most common pathway involves flea bites; infected fleas, especially Xenopsylla cheopis, feed on a rat, inject bacteria from blocked foreguts, and establish a systemic infection. Secondary routes include ingestion of contaminated carrion or contaminated food, and direct contact with the blood or tissues of a dying or dead infected rat. In some cases, maternal transmission occurs when an infected mother passes the pathogen to offspring through milk or during birth.
- Flea bite: infected flea feeds, regurgitates bacteria into the bite wound.
- Ingestion: rat consumes infected tissue or contaminated material.
- Direct exposure: contact with blood or bodily fluids of an infected rodent.
- Maternal transfer: pathogen passes from mother to pups.
Flea biology amplifies transmission. After feeding on an infected host, the bacterium multiplies within the flea’s proventriculus, forming a blockage that impedes blood flow. The flea experiences hunger, attempts repeated feeding, and repeatedly injects bacteria into new hosts. This blockage also increases the flea’s propensity to bite multiple rodents, expanding the outbreak.
Environmental conditions influence the likelihood of infection. High rodent density elevates flea burden, while warm, humid climates promote flea reproduction. Poor sanitation and overcrowded storage areas provide ample hiding places for both rats and fleas, facilitating sustained transmission cycles.
Additional mechanisms, such as cannibalism of infected carcasses and aggressive fighting that creates open wounds, can introduce the pathogen into otherwise unexposed individuals. These behaviors, combined with the flea vector, create a robust network through which rats contract plague.