Why does my pet still have fleas?

So why does this happen? … Well fleas are insects, and so have an egg stage, a larval (maggot) stage, a cocoon stage and a parasitic adult stage.  Incidentally, adult fleas are the only stage found on the pet, and they cannot survive off the pet once they have fed.  The egg, larvae and cocoon are found in the pet’s environment (i.e. off the pet).  Each female flea produces on average 30-50 eggs a day, which fall from the pet and seed the environment.  The eggs hatch into larvae, which eventually spill a cocoon after one to two weeks.  The cocoon stage can survive happily in the environment for at least 6 months.

Most people (understandably) expect, that if they treat their pet for fleas, that they won’t ever see another flea – sadly, this level of flea control is impossible to deliver – for several reasons – but don’t give up hope, there is a way to eradicate fleas.  Be aware that all the flea preventative products are contact insecticides – the fleas have to be on the pet to pick up enough chemical to be killed.

The reason that you see fleas after you have treated your pet is because there is a continual day long procession of fleas arriving on the pet.  These newly arrived fleas die within 24 hours of contact with flea preventative chemicals – but as an observant owner you still notice the fleas.  If you look carefully, you’ll see that some of the fleas are small and unfed, some are bigger (fed) and some are big and lethargic (dying).  There is always a population mix of new arrivals, actively feeding fleas and sick, dying and dead fleas on the pet.

When fully developed, these pre-emerged fleas hatch whenever a pet walks past so they continually appear on the pet.  In effect today’s fleas were last month’s flea eggs.  Within 24 hours of arriving on the pet, the fleas have fed and the egg production cycle starts again.