There are many products available these days to treat pets and premises for fleas. They include insecticides, insect growth regulators and also non-insecticidal products. You can buy them as liquids to be sprayed outdoors and indoors or as foggers/anti-flea bombs which release a fine mist in the air when activated. A veterinarian can help guide you in selecting a product suitable for your needs. Always read product labels and do not hesitate to ask questions that come to your mind. Today we will take a look at different types of insecticides that are used for flea control.
Types of insecticides
An insecticide is a chemical that kills insects or inhibits growth. They work in four different ways based on the types:
- Contact poisons – Fleas get killed when they come in contact with the insecticide. The chemical reaches into the flea’s body through the cuticle and also penetrates the membranes. However, you need to make sure that the fleas come in contact with the substance which means you might have to spray it directly on the parasite.
- Systemic poisons – These are applied topically or fed to the host. When the fleas feed on the blood of treated animals, they are killed by the drug’s stomach poison effect. You can use systemic poisons by applying it to the host animal’s skin or giving it internally in the form of tablets.
- Stomach poison – When ingested by fleas, these insecticides act on their digestive system and kill them. All systemic insecticides are stomach poisons but not all stomach poisons are systemic insecticides.
- Fumigants – These work on the parasite’s respiratory system.
Common insecticides used for flea control
Methoprene or (S)-Methoprene (Precor®)
Methoprene is an off-the-shelf insect growth regulator (IGR). It is known to be highly effective in preventing larval development and adult emergence of different types of fleas. The cat flea or Ctenocephalides felis which is the most common flea species in the United States is highly sensitive to Methoprene. You can get excellent residual effects of this insecticide in larval substrates such as animal bedding and carpets. Administer methoprene at the rate of 2-10mg per kilogram of body weight to inhibit hatching of eggs. You need to use this drug regularly to prevent re-infestation. Toxicity of this drug is low and it is safe for use around humans, birds, bees, fish etc.
Both Pyriproxyfen and Fenoxycarb are IGRs that are even more effective than Methoprene because of their UV photo-stability. This means that you can use them indoors and outdoors for flea control as they are not affected by sunlight. Pyriproxyfen disrupts normal insect growth by mimicking certain hormones. It is highly useful against young flea larvae and eggs. The FDA has approved both these insect growth regulators for use in over 300 registered insecticide products since 1995. You can use both products directly on the pets for flea control. The toxicity of both Pyriproxyfen and Fenoxycarb is low and they are considered safe for use around humans, birds, fish, bees etc.
Fipronil is a relatively new insecticide for flea prevention belonging to the Phenylpyrazole class of chemicals. It works by disrupting the nerves in the brain and spinal cord of the fleas and interfering with GABA chloride gated channels. This leads to uncontrolled activity in the pests resulting in death. Some dogs and cats have shown adverse reactions to fipronil products such as lethargy, dilated pupils, swelling and convulsions. In humans, the insecticide can impact sex hormones and thyroid function. Lab studies have also shown that Fipronil can be toxic to certain birds, fish and bees.
This insecticide was originally developed to mimic nicotine. Today, products with Imidacloprid are available in many different forms like liquids, dusts, granules, etc. They also work in a manner similar to Fipronil, by disrupting the nerve signals and stopping the nervous system from functioning normally. Imidacloprid is more toxic to insects and invertebrates than to birds and mammals. In humans, it can lead to symptoms like dizziness, eye irritation and confusion.
This is a chitin synthesis inhibitor that disrupts chitin development. It is a FDA approved oral drug that works its toxicity through the flea’s digestive system. Lufenuron breaks the flea life cycle at the egg stage; it disrupts the reproductive capability of fleas who fail to produce viable eggs. The unabsorbed lufenuron is excreted in the fecal blood droplets and this fecal matter is toxic to the developing larvae. Lufenuron can be safely administered to cats and dogs up to the rate of 30 mg/kg of body weight. Most pets tolerate this medicine well but some show ocular irritation, decreased appetite and lethargy after prolonged use.
Nitenpyram is a neonicotinoid like Imidacloprid. It works by inhibiting nicotinic acetylcholine receptors and is administered orally to the flea’s host. Nitenpyram is safe for use on puppies and kittens above 4 months of age and works quickly within 30 minutes. No signs of toxicity or overdose have been reported with this drug. Note than Nitenpyram has no effect on fleas in the pet’s environment. So you need to also follow environmental flea control and continue using integrated pest management for preventing re-infestation.
This FDA approved insecticide belongs to the chemical class known as Avermectins. It is for topical use only and you need to administer it at least once a month. The fleas ingest this chemical where it binds to the glutamate gated chloride channels and disrupts feeding and mobility. Apart from flea prevention, Selamectin can also treat mites, mange, roundworms, lice and heartworm. The drug has low acute toxicity.
This is a natural product and a result of fermentation of actinomycete. It activates nicotinic acetylcholine and you can administer it orally to your pet. Spinosad is toxic to adult fleas and produces rapid cessation of feeding and knockdown of fleas. The effect lasts for 48 hours after administration. In humans, Spinosad is used in products for killing head lice. It works by affecting the nervous system of the parasites that feed or touch it. This causes involuntary muscle flexing, paralysis and death. Studies have shown that Spinosad is safe in animals and humans but in extreme cases, it can cause vomiting, eye irritation and redness.
Got fleas? Find out which products work in 2019, with my updated flea control product comparison chart.