Anne Stafferton asked: This one is a bit boring really I've spent hundreds of pounds on flea stuff only for it not to work I breed cats so it's a nightmare I'm now combing them all every day to get fleas out any suggestions on what really really works Answer: Hi Anne, thanks for your question about fleas in cats. I know exactly what you mean – they can be a real nightmare to get under control! I’m going to answer your question by (briefly!) discussing the flea life-cycle and how it can be broken, and then talking about the specific treatments that are available. As a warning, on a blog like this I am legally obliged to use the generic names for all the drugs and medicines (otherwise I would get nasty letters from the Veterinary Medicines Directorate, the government department who regulate advertising of veterinary medicines). You can, however, look up any of the generic names for the active substances and “translate” them into brand names on the VMD’s Product Information Database. What are fleas? Fleas are a group of obligate ectoparasites – this means that they live on the outside of other animals, and cannot survive in any other way but by sucking the blood of their hosts. Once an adult flea lays her eggs, they fall onto the floor, the carpet, and into the cat’s bedding. Here they hatch into larvae, which live, hidden deep in the fabric, in the dust, and in cracks in floorboards etc. The larvae survive primarily by eating the faeces of adult fleas, which fall off the cat as the “black sand” we all know and hate! This material is semi-digested blood, and is very nutritious for the larvae. After their final moult, they turn into pupae (like the chrysalis of a butterfly but less pleasant) and there they stay, waiting for a chance to hatch. Pupae can remain dormant for months or years, and in this state they are more or less impervious to virtually any treatment we can use against them (although apparently repeated steam cleaning can kill them). When they detect air movement, heat, or increased carbon dioxide levels (all indicators that a cat, dog or human is close), they hatch and leap on board, to feed, breed and repeat the cycle. Traditionally, we think of fleas as being a spring and summer problem; however, with modern insulation and central heating, nowadays we see them all year round. The flea life cycle can only complete in a relatively warm environment, but we kindly provide them with a nice warm, comfy house to grow up in. So how do you break the cycle? There are a number of points at which the cycle is vulnerable – however, it’s important to remember that if the cats go outside (even briefly) they can pick up new fleas (deposited by other cats, dogs, foxes and even small mammals such as rodents). It only takes one amorous flea couple to reinfest a whole household… The adult fleas are actually pretty easy to kill – even old-fashioned drugs like fipronil will kill most of the adults present, and many of the newer medications are much more potent. The larvae need to cut their way out of their eggs (using a special “egg tooth” made of chitin); if their synthesis of chitin is impaired (e.g. by lufenuron) they cannot hatch. The larvae cannot develop into adults in the presence of juvenile hormone – if this is chemically supplied (as an Insect Growth Regulator, e.g. S-Methoprene), they cannot make the change into adults. The number of eggs, larvae and pupae in the house can also be reduced, by washing of fabrics (especially bedding) in hot (60C) soapy water. Although it won’t kill all of them, it will reduce the numbers and wash a lot away down the drain where they can’t hurt anyone! The pupae themselves are pretty much impervious to any treatment, but they can be “tricked” into coming out as adults, which are then much easier to kill. The common method is regular vacuuming – the air movement and heat trick the pupae into hatching; you won’t catch many in the cleaner, but once out, they are vulnerable to environmental insecticides. In fact, if you keep a “closed household”, with all the cats (and dogs if you have any) living indoors 24/7, it is theoretically possible to break the life cycle without treating the adults at all… but it will take a long time (the adults may live for 4-6 months) and you’re always at risk of a new introduction (in your clothes, for example). So how do I kill them? As you’ve found, there are a huge range of different flea control products on the market! Broadly speaking, these can be divided into 5 categories: Environmental insecticides: These are products used to spray the infested house, killing adults, sometimes eggs, and larvae. They will not kill pupae, but if applied rapidly after vacuuming, they can be very effective. Most products contain permethrin, which is toxic to cats – this means that you have to be careful using them, by treating rooms one at a time and shutting the cats out until they have ventilated. The cans will explain how long to leave it for on the label, or talk to your vet, before reintroducing the cats. On-cat environmental treatments: These are applied to, or administered to, the cat, to treat the environment, and rely on the fact that the larvae are eating the flea’s droppings. There are 3 particularly important ones:
- Lufenuron – a chitin inhibitor, available as an oral liquid, a tablet, or an injection. Does not kill adults, but prevents larvae and pupae from hatching properly.
- Pyriproxifen – an Insect Growth Regulator, available in some prescription-only fipronil products.
- S-methoprene - another IGR, available in some prescription-only fipronil products.
- Imidacloprid – an insecticide available as a spot-on that kills adults and larvae in the vicinity of the treated cat.