Flea infestations: epidemiology, treatment and control

Fleas (Order: Siphonaptera) are highly specialised insects with more than 2500 species, worldwide. Adult fleas are small (~2–10 mm in length), dark brown, and blood-sucking insects. Although wingless fleas have strong hind legs adapted for leaping, allowing significant mobility.

As holometabolous insects fleas complete a life cycle from egg to adult through larval and pupal stages (Figure 1). A female flea lays up to 50 eggs per day and around 1500 in a lifetime. Fleas lay their eggs in the hair coat of the host, and because eggs are not sticky they fall off the host into the environment. Eggs usually hatch in about 2 to 5 days into larvae. Flea larvae are grub-like and feed on organic debris in the environment, such as flea faeces and dander (Rust and Dryden, 1997). Larvae tend to move away from light and burrow deep into carpets, under furniture or into cracks and crevices. Mature larvae develop into new adults inside a whitish, loosely spun silk-like cocoon, the pupa. Because it is sticky, the cocoon quickly becomes coated with environmental debris, which provides protection from insecticidal treatments and thus, pupae will continue to hatch after pets and the household have been treated. The pupal stage is often the key to an unresolved flea problem and it is thus paramount that veterinary practitioners, nurses and clients understand its complexities.