Fleas are blood-feeding parasites that can be found almost anywhere in the world. The most common flea affecting both dogs and cats is the cat flea, Ctenocephalides felis. Cat fleas are considered permanent ectoparasites, meaning once they locate on a host they do not leave voluntarily. Adult fleas cause irritation and itching, and can cause flea bite anemia, flea allergy dermatitis, and tapeworms in dogs and cats. Fleas will bite a human if an animal is not available, but do not thrive off of human blood. Flea bites can also cause itching and irritation for people.

Fleas undergo a complete metamorphosis like a butterfly or moth. Their life cycle contains an egg, larval, pupal, and adult stage. Warm humid conditions help the life cycle to proceed quickly. An average life cycle takes 3-4 weeks to complete, but can become protracted due to the pupal stage. At any given time during an infestation, the eggs constitute approximately 50% of the population, the larvae 35%, the pupae (cocoon) 10%, and the adults 5%.

A household flea infestation usually begins when adult fleas jump onto the pet. Once on the pet the flea immediately begins feeding, mating, and laying eggs on the pet. The eggs are dislodged from the pet by shaking, scratching, and general movement, and fall to the ground. These eggs will hatch into maggot-like larvae that crawl downward, away from light to pupate (form a cocoon). Often this is deep in carpeting underlying furniture.

Once they have found a dark location, larvae spin a cocoon like a butterfly or moth, incorporating carpet fibers and other debris from the environment. The larvae and pupae are never found on the pet, they exist only in the environment. An adult flea will then emerge from the cocoon to perpetuate the life cycle. Consult your veterinarian for recommendations on the best way to eliminate fleas both on your pet and in your home.