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Environmental flea sprays are often recommended as part of a strategy to tackle a flea infestation. Several brands of flea spray are available, but some are being taken off the market. By doing this module you will:

  • Understand the lifecycle of the cat flea.

  • Know the options available for treating a flea infestation.

  • Be aware of the evidence on the efficacy of environmental treatments.

  • Understand why some products are being taken off the market.

  • Know where to find out which products are authorised for sale.

The cat flea (Ctenocephalides felis) is the commonest cause of flea infestations in cats and dogs and it thrives in the UK. Fleas bites can cause discomfort to the animal and are a common cause of allergic dermatitis in pets. Fleas can also transmit Dipylidium caninum tapeworm (which can infect dogs, cats and people) and Haemoplasma  bacteria (a cause of  anaemia in cats). 

Although cat fleas cannot live and reproduce on people, they can bite leading to skin irritation. They can also transmit bacteria that can infect humans, including Bartonella (the cause of cat scratch disease) and Rickettsia felis (the cause of spotted fever). A flea infestation is unpleasant and can affect the human-animal bond. Flea control is therefore crucial in reducing disease risk and maintaining a strong healthy relationship between pet and owner. 

Having a good understanding of the flea lifecycle is essential for successful flea control and veterinary professionals have an important role in giving accurate advice and educating owners about the flea lifecycle and tlea control.

  • Adult fleas can start to lay eggs within 24–48 hours of their first blood meal and they normally lay around 24–28 eggs per day, mostly at night. 

  • The flea eggs, which are not sticky, fall off the animal as it moves or grooms itself. They hatch 1–10 days later (depending on temperature and humidity).

  • The resulting larvae are free-living and need to feed on adult flea faeces, which contain large amounts of incompletely digested blood, and which is deposited in the environment from the infested host. The larvae also feed on organic debris and on flea eggs in the environment.

  • Flea larvae move away from direct sunlight to dark areas in their environment – e.g. deep into carpet fibres, animal bedding or soft furnishings, or into floorboard cracks or under skirting boards, where there is also a more humid microclimate. Outside they may go under grass, branches, leaves or soil. Flea larvae need a moist environment to survive and are very susceptible to heat and drying out. The larvae are most likely to survive where the cat or dog spends enough time to allow flea faeces to fall into the environment and provide a food source for the larvae.

  • In the following few days, larvae undergo two moults before spinning a silken cocoon and moulting to the pupal stage. 

  • Within about another 1–2 weeks, adult fleas can emerge from pupae. Adult fleas that have emerged from pupae in dark areas move towards a light source. They then jump when the light source is suddenly and temporarily interrupted or if they detect vibrations that indicate a potential host. If the newly emerged adults do not immediately acquire a host, they can survive several days before requiring a blood meal.

  • Once on the host, the flea starts to feed within seconds or minutes, and mates within 8 to 24 hours. So under most household conditions, the whole flea lifecycle can be completed in 3–8 weeks. 

  • However, flea pupae can be very resistant to adverse environmental conditions. Debris in the environment sticks to the outer coat of the pupa, which protects it and also prevents insecticides from getting to the pupa and killing it.  

  • If conditions are unfavourable the pupae can remain viable for several months. This means that an infestation can establish even if mammalian hosts have been absent for some time. Pupae hatch in response to heat and movement and so are reactivated by the presence of possible hosts, including cats, dogs, rabbits, ferrets and wildlife such as foxes and hedgehogs, or for example, when people move into new home. 

  • The speed and reproductive potential of the flea lifecycle means that just a few adult fleas can lead very quickly to heavy environmental contamination of homes, particularly when temperatures are higher. Central heating in the home means that fleas can be active all year round and the higher temperatures speed up the lifecycle. So by the time fleas have been found on the animal, an infestation may have already established in the home. 

To control a flea infestation, all the susceptible animals in a household (whether or not they obviously have fleas) need to be treated simultaneously with a product that kills adult fleas (adulticide). The products must be administered frequently enough to continue to prevent flea egg laying. Check the relevant product information to know the correct frequency.

It can take several months to effectively control an infestation, and so it is important to help pet owners understand this. Click here to read a case report of fleas on treated cats in a new home in Preston. 

The results of a published randomised controlled trial show how long it can take to control an infestation (Dryden et al. 2000 - see the reference list at the end of the module). In the trial, naturally-infested dogs in homes in Florida were treated with a monthly spot-on for 3 months. While flea counts on the dogs reduced by 90–98% within 1 week of treatment, the same reduction in flea counts in the home environment did not occur until 1 month after treatment, and after 3 months’ treatment fleas in the environment were still not completely eliminated.

An alternative to an adulticide is to treat all susceptible pets continuously with lufenuron (brand name Program), which prevents flea eggs from hatching after fleas have fed on the treated host. However, this does not kill adult fleas, so an adulticide is also needed to reduce adult flea load in an existing infestation. 

Anything that helps to reduce the number of eggs and larvae will in turn reduce the number of pupae in the environment, which in turn should reduce the time needed to bring an infestation under control as well as reduce the number of flea bites that pets and owners receive. The options for environmental control are physical cleaning and use of environmental insecticides.

Vacuuming is useful in reducing and killing pupae, eggs and larvae in households, and daily vacuuming is important in helping to prevent infestations. However, vacuuming on its own is unlikely to be effective for dealing with an infestation. Washing pet bedding at 60 degrees Centigrade will also help to reduce environmental stages. There is no evidence that conventional household cleaning products have any impact on fleas, larvae or pupae.

Products that are used to treat the infested environment directly contain pyrethroid insecticides, alone or together with an insect growth regulator, or alternatively, dimeticone. 

  • The pyrethroids include cypermethrin, deltamethrin, permethrin and tetramethrin.  “Flea bombs” or fogging devices contain a pyrethroid at higher concentrations than in flea sprays. Pest control companies use products containing pyrethroids to fumigate homes with large infestations or sources of infestation that are difficult to access. Pyrethroids will reduce larvae and egg numbers significantly if exposure to the insecticide is adequate.  

  • Some environmental flea sprays contain an insect growth regulator in combination with pyrethroids. This group includes methoprene, S-methoprene and pyriproxyfen. The drugs act by interfering with the hormonal control of growth in immature fleas, preventing development from one larval stage to the next and leading to larval death. 

  • The use of dimeticone in spray form has been developed as an environmentally-friendly alternative to traditional insecticides. Dimeticone is a synthetic oil (silicone) used in a wide range of products including insecticide-free head-lice treatments for humans. Environmental sprays containing dimeticone have the advantage of being able to be used if there are pet invertebrates or fish in the household. It works by creating a surface film of dimeticone on adult fleas and larvae, so inhibiting movement of the cuticular joints and causing immobilisation. Adult fleas can be prevented from emerging if cocoons are adequately exposed. However the dimeticone spray has not been shown to last more than 3–4 weeks after application. This is a disadvantage compared with many flea sprays, which can persist in the environment for many months.

When treating the environment directly, all areas where pets frequent, such as cars, furniture and bedding must be treated, paying particular attention to areas in, and around, which the animal sleeps, because these areas will have the greatest concentration of eggs and developing stages. Sprays need to be used from the correct distance to ensure effective penetration of chemicals. Objects such as children’s car seats, pillows, and cushions may need to be removed and treated separately. 

Care is needed when using insecticide products containing pyrethroids because of the potential for pyrethroid toxicity. Fish, invertebrates and cats are particularly susceptible but any animal may be affected. Therefore pets should be removed from the areas to be treated and fish and invertebrates removed from the premises before treatment. Treated areas should be well ventilated during treatment and for at least 1 hour afterwards. 

No central agency regulates efficacy standards for flea sprays but companies producing flea sprays make claims about the duration of effect from their own studies. Claims commonly include activity against environmental flea life stages for 6 months and larval growth regulation for 12 months. 

There is little comparative information on flea sprays, or studies comparing different infestation treatment strategies, including pet treatment with or without environment treatment. It is assumed that pyrethroids and growth regulators will reduce flea numbers in the environment over time and that this will reduce the time needed to eliminate an infestation if an effective adulticide is also being used on susceptible animals in the home. 

Environmental flea sprays containing insecticides are classed as biocidal products, which are regulated by the Health and Safety Executive. Since 1998, when biocides were under the UK Control of Pesticides Regulations (COPR), regulation has been transferred to the EU and now comes under the EU Biocides Regulation (BPR, Regulation (EU) 528/2012) (HSE 2018). The change has required all active substances used in biocidal products to be reviewed and approved at an EU level, an ongoing process that is expected to continue until 2024. Products containing dimeticone are exempt from regulation under this Directive because they fall within the classification of a physically-acting approach. As a result of the regulatory changes, which have required companies to submit dossiers on their products, some companies have opted to reformulate products or take their products off the market. Some products are no longer available, and the following are being discontinued:

  • Acclaim – Cannot be sold since 2 July 2018, but customers can continue to use legally until 3 January 2019. 

  • Indorex – Cannot be sold after 28 December 2018, but customers can continue to use until 30 June 2019.

The regulatory changes will have a negligible effect on environmental treatment options because similar products will continue to be available: for example, Beaphar Home Flea Spray; Frontline Homegard Spray; Permaguard, RIP Fleas Extra, Staykil (reformulated).

Veterinary professionals need to keep up to date with flea spray availability as legislation changes. Up-to-date Information about the regulatory status of environmental flea sprays can be found in the COPR database

When tackling an established flea infestation, reducing the flea lifecycle stages from the environment through physical cleaning, hot washing of bedding and use of environmental sprays is probably a helpful addition to using flea control products on pets. The products available for treating the environment contain pyrethroid insecticides, insect growth regulators or dimeticone. We know surprisingly little about the efficacy of environment treatments in tackling flea infestations, including the comparative efficacy of different products or strategies. A good understanding of the flea life cycle is crucial to managing an infestation and a clear explanation should help manage pet owners’ expectations. 

Regulatory changes mean that some flea sprays are being taken off the market voluntarily by suppliers. Pet owners should be reassured that any alternatives are likely to have similar efficacy and that previous products have been withdrawn due to legislative changes rather than any concerns about lack of efficacy or safety. 

Podcast

You can listen to a complete podcast of the module by using the play button below or use the download link on the right-hand side of the player to download the podcast to your mobile device.

Flea-infestations-test-your-knowledge.jpg

References

Blagburn BL, Dryden MW. Biology, treatment, and control of flea and tick infestations. Vet Clin Small Anim 2009; 39: 1173–200.

Dryden MW, Rust MK. The cat flea: biology, ecology and control. Vet Parasitol 1994; 52: 1–19.

Dryden MW et al. Control of fleas on naturally infested dogs and cats and in private residences with topical spot applications of fipronil and imidacloprid. Vet Parasitol 2000; 93: 69-75.

Health and Safety Executive. Revision of the Biocidal Products Directive (98/8/EC) [online].

Health and Safety Executive. COPR database [online]. [Accessed 28.9.18

 Hink WF. Vacuuming is lethal to all postembryonic life stages of the cat flea, Ctenocephalides felis. Entomol Exp Appl 2007; 125: 221–2. 

Jones IM et al. 0.4% dimeticone spray, a novel physically acting household treatment for control of cat fleas. Vet Parasitol 2014; 199: 99-106. 

Kern WH et al. Diel patterns of cat flea (Siphonaptera: Pulicidae) egg and fecal deposition. J Medl Entomol 1992; 29: 203-6.