A LONG time ago I went to view a house for sale. It had been empty for months but still had the carpets and curtains. After a few minutes I became aware of something on my legs. Looking down I saw fleas all over my feet and hopping up my shins. Needless to say I left quickly and brushed them all off, and I did not have any further interest in the house. Thus it was that I became an expert in the life cycle of the flea.
Dogs and cats have specialist fleas. This is a cat flea (Ctenocephalides felis), which also lives on dogs,
and this is a dog flea (Ctenocephalides canis), which also lives on cats.
Both prefer their own hosts but are not fussy about what kind of blood they drink, and do not turn up their noses at human blood either.
The fleas lay their eggs in the animal’s fur. These tend to fall off into the host’s bedding or into carpets as the animal moves round the house. They hatch into larvae which feed on any organic matter they can find, such as dead insects, skin flakes or other eggs. After between four and 14 days they weave a cocoon and pupate while they metamorphose into adults. This takes only a few days and when they detect their host passing, for example by footfalls or body heat, they hatch and jump on to the animal. Here is the clever bit – if the cycle is interrupted, for example by the host moving out of the house, leaving it empty, the pupal stage can last for months until triggered by vibrations, warmth or sound, such as you might get when someone is looking round a house for sale. At this point they burst out of their cocoons and race to the source of blood. So although the original dog or cat host had long gone, when I set foot in the house it was like an alarm clock to the fleas-to-be. You have to admire them, don’t you?
Fleas have been in the news recently because it has been found that treatments to keep pets free of them are poisoning the waterways. The treatments, such as Frontline Spot On and Advantage, contain either fipronil or imidacloprid. The latter is a neonicotinoid and the former is similar. Such chemicals have been banned from agricultural use because of their harmful impact on the environment but are still permitted for pet treatments. They get into streams and rivers after owners bathe their pets or wash their bedding. There they kill the larvae of insects such as mayflies and dragonflies, in turn reducing the food supply for birds, bats, freshwater fish and amphibians.
Researchers from Sussex University say that owners are giving the treatments to their pets far more often than necessary, up to once a month. Professor Dave Goulson says that most dogs and cats do not have fleas most of the time, and do not need to be treated prophylactically, only when fleas appear. He says that alternative, less harmful products are available and recommends washing bedding regularly to kill flea eggs, larvae and pupae.
I hope all that doesn’t leave you with an uncontrollable need to scratch yourselves.