Flea

Brief:

The most common species of flea in Australia is the cat flea, Ctenocephalides felis. Also present is the dog flea, Ctenocephalides canis, and the human flea, Pulex irritans. The latter two species are relatively rare and, despite their common names cat fleas mostly infect dogs and people.

Fleas are blood-sucking parasites. They actually belong to an order of insects known as Siphonaptera, literally ‘wingless siphon’. Historically fleas were associated with the death of more than 200 million people in the 14th Century through the spread of the bubonic plague. Nowadays they are mostly known for their irritation and revulsion when seen on pets.

Habits

Adult fleas range in colour from a light brown to a dark mahogany and, when viewed with the naked eye, they are roughly an oval shape. They are flattened laterally (on their side) which allows them to quickly move through their host’s hair. The adults measure around 2 – 8 mm in size and are covered in a series of bristles and combs that enable them to ‘get stuck’ in the hairs of their host so they are not easily removed. They have two short antennae on the head and a very large and well-developed pair of rear legs. These powerful legs enable them to leap over 30 cm to attach themselves to a host, or escape from danger. Both male and female fleas rely on blood for their nutrition, though they can survive for many months in a dormant state if a blood meal is not available. To feed, a flea attaches to its host and crouches down low; it then uses its mouthparts in a sawing motion to cut into the skin. It injects a small amount of an anti-coagulant with its saliva into the wound to keep the blood flowing. Typically fleas are seen biting lower limbs and the bites are usually clustered together.

Females use blood to nourish their eggs and will lay up to 4 eggs after each blood feed. Over their life cycle of several months, a female flea will typically lay around 100 eggs. The eggs are a white to cream colour, oval in shape and only about 0.5mm in length. They can hatch in as little as one week, though they can lie dormant for many months. The larvae that hatch from the eggs are like small white maggots, about 3 mm in length, and sparsely coated with very fine hairs. They have no legs and wriggle around in search of food, usually skin scales or undigested blood excreted by the adults. They will hide away in cracks and crevices for shelter and are rarely seen.

Larvae go through four moults (instars) over a 1 – 3 week period. The life cycle is faster in warmer conditions. The final instar larvae will pupate by spinning a silken cocoon. Inside their cocoon they will transform over a period of 1 – 2 weeks into an adult flea, though they can remain dormant in the cocoon for many months, often emerging only when they feel vibrations from a potential host.

Habitat

Fleas can live on any warm-blooded animal, but seem to prefer to live on humans, cats, dogs, possums, rats and other rodents. In homes they may be found on shoes, pant legs, blankets, carpets, floorboards and pet bedding.

Threats

The main flea species encountered can survive on a range of host species and have been known to transfer pathogens including viruses, bacteria and other parasites. They are a natural host for the double-pored tapeworm, Dipylidium caninum, that commonly infests dogs and cats, but which can also be transmitted to humans. Currently the only reported flea borne disease in Australia is murine typhus, which is transmitted from rats to humans by the rat flea Xenopsylla cheopis. This disease is relatively rare nowadays in Australia.

Since fleas continually bite, they cause a great deal of stress and irritation when present. Some people will also develop a reaction to the flea saliva resulting in a wheal surrounding the puncture site that might develop after 10 – 30 minutes; this is usually exceptionally itchy too. These wheals may develop over the next 24 hours into small lesions. Fleas are also a major cause of papular urticaria, an allergic reaction to insect bites, especially in children. If they constantly scratch the bites, additional inflammation can develop, which in turn may lead to secondary infections.

Prevention

Typically control involves a regime of hygiene and housekeeping measures, including regular vacuuming, treatment of pets and their bedding, and chemical treatment of the infested areas of the property. There is a wide range of proprietary treatments available for fleas on animals. Pet bedding should be treated and then either thoroughly washed or destroyed.

A professional pest manager will treat the areas where fleas are active, and into harbourages where the flea larvae may be present. Sandy areas around the home and the subfloor region are also a common refuge for fleas that will need to be treated. There is a wide range of registered products available to professional pest managers who can be relied upon to select the most suitable for the situation.

Others

Article prepared by Steve Broadbent, Ensystex Australasia Pty Ltd on behalf of the Australian Environmental Pest Managers Association. Photographs courtesy of, and copyright of, Dr Stephen Doggett.

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