By: Jean Morgan
Where there are dogs and cats, there are fleas. These persistent little parasites cause no end of problems for pets and their owners. Sometimes it seems no matter what we do to kill them, our pets are still infested with the little blighters. Why are they so hard to get rid of?
Let’s have a closer look at the lifecycle of the flea. An adult flea will bite your dog or cat and have a blood meal. It will then 50- 100 eggs each day which will fall off your pet into the environment – your backyard, your pet’s bed, your carpet. These eggs take up to a few weeks to hatch, depending on the temperature and humidity. When they hatch, the larvae actively seek warm, humid, shady areas to further develop, as they are very susceptible to heat and drying. As larvae, they undergo three developmental stages and feed mostly on the feces of adult fleas which contain dried blood, as well as organic debris. This stage can take up to 3 weeks.
Mature larvae produce a sticky cocoon, which protects them from heat and most insecticides. Adults emerge from the cocoon in response to high humidity, warm temperatures or vibrations. This can take anywhere from two weeks to a year, depending on conditions. I’ve heard many times about people who go on extended holidays and come home to a flea plague – the vibration caused by them walking through their house has stimulated the hatching of dormant cocoons. These adult fleas then have a blood meal and the cycle starts again. So, although your pet and home could be flea free right now, you may have an infestation again within a few weeks.
It’s very important to understand the flea lifecycle so we can choose flea control products that are effective. Keeping in mind that the number of adult fleas on your pet represents only 1% of your total flea population, it’s easy to see why just using adulticides may not be effective. Read that again – for every flea you see on your pet, there are another 99 in the environment as eggs, larvae or cocoons. That, I believe, is the main reason fleas are so hard to control. You need to break the lifecycle to reduce the flea population on your pet.
Given that the cocoon is resistant to insecticides, our only options are to kill the adults, kill the larvae or kill the eggs. As far as adulticides go, any of the “spot on” products are very effective – Advantage, Frontline or Revolution. Advantage also has the added effect of killing larvae before they develop into pupae, thus breaking the lifecycle. Frontline Plus contains (S)-methoprene which is an insect growth regulator. This chemical is related to a juvenile growth hormone in the flea, and its presence allows the larva to develop into a pupa, but the pupa never emerges as an adult. Lufenuron in Program and Sentinel is another insect growth regulator which stops the production of chitin in the larval flea. Chitin is essential for the larvae to hatch from the egg, so no chitin means eggs don’t hatch. Also, the adult flea will excrete Lufenuron in her faeces, and when the larvae feed on this, they also don’t produce chitin. Chitin is essential for production of the external skeleton of the flea, so the larvae also die. Since Lufenuron relies on the adult flea biting the pet, it’s not a good option on it’s own for allergic dogs and cats.
I believe there are three steps to effective flea control in dogs and cats. Firstly, use an effective adulticide to stop the fleas biting your pet. Secondly, use a product that breaks the lifecycle to stop the constant reinfestation. Thirdly, don’t give up. Keep up with the flea control even when you don’t see fleas.
