Having a thorough understanding of flea biology and knowing how to treat the various life stages is critical for gaining control of problem flea populations.
Fleas are often considered an ‘occasional’ pest. However, for anyone suffering from a flea infestation, it is likely one of the most annoying and painful pest problems they will experience. In addition, although the days of the plague – the ‘black death’ – are long gone, a flea bite can still pass on some debilitating diseases. Getting on top of a flea infestation requires a comprehensive treatment. Being knowledgeable about fleas and the treatment process required will certainly help in winning flea jobs.
Fleas aren’t just fleas. In fact, there are some 2500 species of fleas globally, although there are only 88 species in Australia, 78 of which are endemic.
However, only a few species are considered pests and can impact human health. The most common flea found in homes is the cat flea, Ctenocephalides felis. Despite its name, it is found on a wide range of pets, including dogs. Although the dog flea, Ctenocephalides canis, is regularly mentioned, it is not very common and documented infestations in Australia are rare.
The second most common flea humans are likely to encounter in Australia is the oriental rat flea, Xenopsylla cheopis. Occasional infestations by Pulex irritans, the human flea, also occur. Pulex irritans is also called the common flea, due to its ability to feed on a wide range of hosts and its widespread presence in human homes with hygiene issues. Although common in years gone by, nowadays it is far less of a problem for humans due to improved hygiene.
Fleas are also found on poultry (Echidnophaga spp.). They are sometimes called stick-fast fleas as they do not jump when disturbed. They rarely cause a problem for humans, although anyone in contact with infested birds could get bitten.
Species Snapshot – Cat flea
Latin name: Ctenocephalides felis.
Common name(s): Cat flea.
Description: Small, wingless insect, 1-3 mm long. Laterally compressed (thin from side to side).
Native distribution: Invasive, believed to have originated in Africa.
Current distribution: Worldwide.
Location: Adult fleas live all their lives on their host, all other life stages in nearby suitable substrates.
Diet: Adults feed on blood from their host. Larvae feed on organic material in substrate with critical need for undigested blood excreted by adult fleas.
Sting/bite: Fleas have a painful bite, using their piercing and sucking mouthparts to obtain a blood meal (including from humans).
Identification and life cycle
Flea eggs are small, around 0.5 mm in size and white in colour. They have a smooth surface and fall off the animal shortly after being laid. They are virtually impossible to see without magnification. They hatch within two days.
The emerging flea larvae burrow down into the surface after hatching to get away from the light, typically in carpet, cracks in floorboards, or outside in soil. Here they eat organic material but prefer ‘flea dirt’, the undigested blood excreted by adult fleas. They are hairy, translucent ‘worms’ that can also be hard to spot. The larvae moult through three instars and range from 1.5 to 5mm long.
When ready to metamorphose into an adult, the larvae spin a cocoon of silk and the surrounding dirt and debris stick to the outside, making them difficult to spot. This cocoon is very difficult for insecticides to penetrate.
After one to two weeks the adult flea is ready to emerge, but won’t do so unless a potential meal is nearby. They pick up on the presence of a potential host by sensing the vibrations made by large animals. On picking up the vibrations, they emerge rapidly from their pupa and use their amazing jumping power to leap from the ground to the animal above.
Adult fleas live all their lives on their host, where they obtain blood meals using their piercing and sucking mouthparts. Adult cat fleas are up to 3 mm long and are compressed laterally (they are thin from side to side), which allows them to move easily between the hair, fur and feathers of their host.
Fleas need warm, humid weather to complete their life cycle. In particular, the larvae are susceptible to drying out and dying in humidity below 45%, which is why fleas are generally confined to the coastal regions of Australia. They also require a temperature above 15 C to complete their development. Put these two factors together and it’s easy to see why summer is flea season and why a wet, humid summer makes for a big flea season. Although fleas shouldn’t be a winter problem in the cooler parts of Australia, homes that have heating can still allow flea infestations to develop, providing the humidity is high enough.
Fleas are normally seen as irritating, rather than carriers of disease, but it’s easy to forget that fleas had a significant role in the most fatal pandemic recorded in human history. The ‘Great Plague’ that raged through Africa and Eurasia between 1346-1353 was estimated to have killed 75-200 million people. Put into context, the total confirmed number of Covid deaths so far is just under six million. The plague or ‘black death’ is caused by the bacterium Yersinia pestis, which is passed to humans through bites of the rat flea. Although uncommon and not present in Australia, there are over 500 cases per year globally with around a 20% mortality rate.
In Australia there are some diseases that are passed to humans through flea bites, such as the rare cat-flea typhus and more common murine typhus (Rickettsia typhi). Murine typhus is found throughout Australia but is more prevalent in warmer areas. Transmission can be through a flea bite or through contact with contaminated flea or rodent faeces (that may become airborne when cleaning). At first, flu-like symptoms and a rash occur one to two weeks after exposure, followed by vomiting and neurological symptoms (balance issues, confusion, seizures) as the disease progresses.
Fleas can also cause diseases in pets, including cat scratch fever (Bartonella henselae) and tapeworms. Cats can pass cat scratch fever to their owners through licking. Cat scratch fever can impact a wide range of organs, and is more likely to occur in immunocompromised individuals and young children. Similarly, children can become infested with tapeworms when they lick their dirty hands or toys which may have traces of pet faeces.
Best practice treatments
To carry out a successful flea treatment, it is necessary to be thorough. After undertaking an inspection to confirm the presence of fleas, a number of steps should be followed, some of which will require the help and cooperation of the homeowner.
Step 1: Clean and vacuum
Vacuum the whole house, especially carpets, upholstery, under furniture, edges of rooms and cracks in floorboards. The contents of the vacuum cleaner should be sealed in a plastic bag and placed in the bin. Vacuuming can eliminate over 90% of eggs, larvae and adults. It also stimulates any mature pupae to hatch.
Step 2: Washing infested items
Recommend that the homeowner wash infested items, such as sheets and pet bedding. Placing items in a plastic bag, sealing the bag and placing it in the sun for several hours will kill any fleas inside.
Step 3: Treat inside and outside the home
Before treatment ask the homeowner to clear away belongings, especially any toys. It’s important to treat everywhere the pet has been as eggs will fall off wherever they go. As well as a comprehensive treatment inside the home, it is necessary to treat pet resting places outside the home. Ask the homeowner where their pet hangs out – it is likely to be in cool shady areas (under the house or under trees), the kinds of places flea larvae thrive.
Products to use
A residual spray labelled for fleas will kill any eggs, larvae and adults present and provide lasting protection – generally 3-6 months depending on the product. It is best practice to also include an insect growth regulator, as an IGR is both longer lasting than residual sprays and active at extremely low doses. Including an IGR in the spray mix means the treatment can last for an extended period. With an IGR remaining active in the substrate for longer periods than the residual insecticides, it continues to work to break the flea breeding cycle, preventing new flea infestations from developing. If the homeowner is concerned about using sprays around their pets, using an IGR on its own in the pet resting places is a great option.
It is important to be aware that the flea pupae are generally impervious to insecticides. As such, any pupae that are present at the time of treatment will still be viable and adults can emerge any time over the next one to two weeks. Even though a residual treatment should be present on the surface, the fleas can emerge from the pupae and bite the homeowner without picking up insecticide or picking up a sub-lethal dose. It is worth flagging this possibility to the homeowner at the time of treatment and perhaps incorporating the possibility of a supplementary treatment in the price. However, if a thorough vacuum is carried out before the first treatment the chances of this occurring are far lower, as the number of pupae present will be significantly reduced.
Don’t forget the pet!
As pest managers we should not treat (!) or make any recommendations about treatments for the customer’s pets. However, it is important the homeowner seeks veterinary input on what flea treatment is required and this should be carried out at the time of the pest control treatment.
Fleas can jump up to 30 cm or about 200 times their own body length!
The biggest flea in the world is the mountain beaver flea, Hystrichopsylla schefferi, which is up to 13 mm long! The biggest flea in Australia is Bradiopsylla echidnae, which feeds exclusively on the echidna, and is a more modest 4 mm in length.