How do fleas transmit infections? - briefly
Fleas spread disease by biting an infected host, then transferring pathogens to a new host through contaminated mouthparts or by regurgitating infected material during feeding. They also excrete pathogen‑laden feces that can enter a host’s bloodstream via skin abrasions or ingestion.
How do fleas transmit infections? - in detail
Fleas act as biological vectors by acquiring pathogens during a blood meal and delivering them to subsequent hosts. When an infected flea ingests blood, microorganisms such as bacteria, viruses, or protozoa survive within the insect’s gut or migrate to the salivary glands. During later feeding, the flea injects saliva containing the pathogen into the host’s skin, establishing infection.
Key mechanisms include:
- Gut colonization: Pathogens persist in the flea’s digestive tract, multiplying or forming cysts that resist digestive enzymes.
- Salivary transmission: Some agents move from the gut to the salivary glands, where they are released with saliva during probing.
- Regurgitation: Fleas may expel part of the ingested blood back into the bite site, introducing organisms present in the previous meal.
- Fecal contamination: Certain bacteria are excreted in flea feces; host scratching or grooming can introduce these organisms through skin abrasions.
Specific examples illustrate these pathways:
- Yersinia pestis (plague) multiplies in the flea’s foregut, forming a blockage that forces the insect to regurgitate bacteria during feeding.
- Rickettsia typhi (murine typhus) is transmitted through infected flea feces that enter the host via skin lesions.
- Bartonella henselae (cat‑scratch disease) is shed in flea saliva and feces, contaminating scratches and bites.
Environmental factors such as temperature, flea species, and host immunity influence pathogen survival and transmission efficiency. Control measures that interrupt feeding cycles—chemical insecticides, host grooming, and environmental sanitation—reduce the likelihood of vector‑mediated infection.