What does a flea feed on when parasitizing a human and what disease does it transmit? - briefly
When a flea bites a person it consumes blood. It can transmit the bacterium Yersinia pestis, the agent of plague.
What does a flea feed on when parasitizing a human and what disease does it transmit? - in detail
Fleas are obligate blood‑sucking ectoparasites. When a flea attaches to a human host, its piercing‑sucking mouthparts penetrate the epidermis and draw capillary blood into the foregut. Saliva injected during feeding contains anticoagulants and anesthetic compounds that facilitate rapid blood intake while minimizing host detection. The ingested blood provides the protein and lipid resources required for egg production and metabolic maintenance. Fleas can ingest several microliters of blood per meal, enough to sustain adult survival for several days before another feeding is needed.
The primary pathogen transmitted by a flea that feeds on humans is Yersinia pestis, the bacterium responsible for plague. After a flea ingests an infected blood meal, the organism multiplies in the proventriculus, forming a biofilm that obstructs the digestive tract. This blockage triggers repeated, aggressive biting attempts, during which bacteria are regurgitated into the bite wound, establishing infection in the new host. Plague manifests in three clinical forms—bubonic, septicemic, and pneumonic—each associated with distinct symptom patterns and mortality rates if untreated.
Additional agents occasionally spread through flea bites include:
- Bartonella henselae – causes cat‑scratch disease; transmission to humans is rare but documented.
- Rickettsia typhi – the agent of murine typhus; flea feces may contaminate skin abrasions, leading to infection.
- Dipylidium caninum – a tapeworm; humans acquire the larval stage by ingesting infected flea fragments.
Transmission efficiency depends on flea species, feeding frequency, and the pathogen’s ability to survive within the insect’s gut. Prompt removal of fleas and appropriate insecticide use reduce exposure risk, while prophylactic antibiotics are indicated for high‑risk contacts with plague‑endemic vectors.