Which fleas transmit plague? - briefly
The primary plague vector is the oriental rat flea, Xenopsylla cheopis, while other competent species include Xenopsylla brasiliensis, the human flea Pulex irritans, and various rodent‑associated fleas such as those in the genus Ctenophthalmus.
Which fleas transmit plague? - in detail
Fleas that serve as vectors for Yersinia pestis include several species adapted to rodents and, in some cases, humans. The most efficient transmitter is the oriental rat flea, Xenopsylla cheopis. It thrives in warm, humid environments, feeds frequently on rats, and can maintain the bacterium in a blocked foregut, forcing repeated attempts to feed and increasing transmission risk to new hosts.
Other rodent‑associated species capable of spreading the pathogen are:
- Ctenophthalmus spp., common in European and Asian rodent populations; they can acquire infection during blood meals and transmit it to other rodents.
- Nosopsyllus fasciatus, prevalent in North America; experimental studies show it can support bacterial growth and pass the infection during feeding.
- Leptopsylla segnis, found in tropical regions; documented to carry Y. pestis in field surveys.
The human flea, Pulex irritans, occasionally bites humans and can act as a secondary vector, especially in outbreak scenarios where rodent fleas are scarce. Although its competence is lower than that of X. cheopis, it has been implicated in historical plague epidemics.
Transmission dynamics depend on several biological factors:
- Blocking – the bacterium forms a biofilm in the flea’s proventriculus, obstructing blood flow and prompting the insect to regurgitate infected material.
- Feeding frequency – species that feed multiple times per day increase the probability of infecting new hosts.
- Host preference – fleas that readily switch between rodents and humans bridge enzootic cycles and human outbreaks.
- Environmental tolerance – species thriving in diverse climates expand the geographic range of plague risk.
In summary, the primary vector is Xenopsylla cheopis, supplemented by Ctenophthalmus, Nosopsyllus fasciatus, Leptopsylla segnis, and, under certain conditions, Pulex irritans. Their biological traits collectively determine the efficiency and spread of plague across rodent reservoirs and human populations.