fleas

Fleas are small wingless insects in the order Siphonaptera. They are obligate ectoparasites of mammals and birds, feeding exclusively on blood. Fleas are typically 1.5–3 mm long, laterally compressed, and have powerful hind legs adapted for jumping between hosts and through fur or plumage.

Most species have a close association with a primary host group. The cat flea (Ctenocephalides felis) is the most widespread parasite on domestic cats and dogs and can also bite humans. Other species include the human flea (Pulex irritans) and dog flea (Ctenocephalides canis). Fleas often live in the host’s environment, such as bedding, carpets, or soil, where eggs and larvae develop.

Fleas undergo complete metamorphosis with four life stages: egg, larva, pupa, and adult. Eggs are laid on the host or in the surrounding environment; larvae feed on organic debris, including dried blood, and avoid light. Pupae develop in cocoons and may remain dormant for long periods, resisting desiccation until cues such as a nearby host, heat, carbon dioxide, or movement trigger emergence of adults, which begin blood meals.

Adult fleas are primarily vectors of disease and can cause itching, dermatitis, and, in heavy infestations, anemia. They transmit pathogens such as Yersinia pestis (plague) and Rickettsia typhi (murine typhus) in some settings, and can carry Bartonella spp. affecting humans and animals.

Control relies on integrated measures: treating pets with approved insecticides or oral medications, regular cleaning of bedding and living areas, vacuuming to remove eggs and larvae, and reducing wildlife reservoirs. Preventive strategies include ongoing pet treatment and minimizing environments where fleas can develop.