How do fleas transmit plague? - briefly
Fleas acquire Yersinia pestis by feeding on infected rodents; the bacteria multiply in the flea’s foregut, forming a blockage that causes the insect to regurgitate the pathogen into the bite wound of subsequent hosts.
How do fleas transmit plague? - in detail
Fleas acquire the bacterium Yersinia pestis when they feed on an infected mammal, most commonly rodents. The pathogen multiplies in the flea’s foregut, forming a dense blockage known as a “biofilm” that impedes blood flow. This obstruction triggers repeated attempts to feed, causing the flea to regurgitate infectious material into the bite wound of a new host. The regurgitated bacteria enter the host’s bloodstream, initiating infection.
Key physiological events:
- Ingestion of infected blood during a blood meal.
- Replication of Y. pestis within the proventriculus, producing a polysaccharide matrix.
- Formation of a proventricular blockage that creates feeding difficulty.
- Repeated probing leads to mechanical expulsion of bacteria into the skin.
- Transfer of bacteria directly into the dermal capillaries, where they disseminate systemically.
Environmental factors such as temperature and humidity influence bacterial growth rates and blockage development, affecting transmission efficiency. Flea species with strong proclivity for forming foregut obstructions, such as Xenopsylla cheopis, are the primary vectors in historic plague pandemics. Control measures that interrupt any of these steps—reducing rodent reservoirs, limiting flea populations, or preventing flea bites—directly diminish the risk of plague spread.