What does a flea feed on when parasitizing a human, and what infection can it transmit? - briefly
When a flea infests a person, it consumes the host’s blood. The bite can act as a vector for Yersinia pestis, the bacterium that causes plague.
What does a flea feed on when parasitizing a human, and what infection can it transmit? - in detail
Fleas that bite people obtain their nutrition exclusively from the host’s blood. The insect inserts its piercing‑sucking mouthparts into the skin, lacerates capillaries, and injects saliva containing anticoagulants and anesthetic compounds. The blood is drawn into the foregut, where enzymes begin digestion. A single blood meal can provide enough protein for the female to develop dozens of eggs, prompting repeated feeding on the same or different human hosts.
The primary pathogen transmitted by human‑biting fleas is the bacterium that causes plague. When a flea ingests blood from an infected rodent, Yersinia pestis multiplies in the gut and forms a blockage. During subsequent feeds, the flea regurgitates bacteria into the bite wound, initiating bubonic or septicemic plague in the human host. In rare cases, inhalation of respiratory droplets from a plague‑infected patient can lead to pneumonic plague, but the flea bite remains the classic route of entry.
Additional infections linked to flea feeding include:
- Bartonella species – flea saliva can carry Bartonella henselae, responsible for cat‑scratch disease and occasional febrile illnesses in humans.
- Rickettsia typhi – the causative agent of murine typhus; transmission occurs when flea feces contaminated with the organism are scratched into the skin.
- Dipylidium caninum – the canine tapeworm; humans acquire the parasite by ingesting infected flea larvae or adult fleas containing cysticercoid larvae.
Each of these agents relies on the flea’s blood‑feeding behavior to move between hosts. The combination of anticoagulant saliva, repeated bites, and the potential for flea gut blockage makes the insect an efficient vector for serious bacterial and parasitic diseases.