Ctenocephalides felis (Cat Flea)
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A cat flea Ctenocephalides felis waits on the carpet for a passing cat, dog or
Of the nearly 100 species of flea found in southern Africa, the cat flea, Ctenocephalides
felis, is usually the species responsible for causing human discomfort. Its favourite
hosts are rats, cats and dogs, although it will also feed on humans, given half a chance.
Your dog is more likely to have cat fleas than the rarer dog fleas, Ctenocephalides
canis. The eggs of cat fleas are oval, white and large in relation to the size of the
adult (c. 0.5 mm long). They are laid in the fur of the dog or cat and can easily end up
on the floor when the animal scratches or shakes itself. The worm-like larvae live in
crevices of floors, in and under carpets, but most commonly they are found in the cat or
dog's bedding. They feed on organic matter such as flea faeces and dry blood. The blood
usually originates from the adults who squirt it from their anuses while feeding on the
host. This explains why a flea in your bed will leave flecks of blood on the sheets.
At the end of its development, the larva constructs a silken cocoon within which it
pupates. In the pupal stage of insects, the genes 'turn on' the production of a new set of
cells that will form the adult. Most of the old larval cells are broken down. In cat
fleas, the adult does not normally emerge from the pupa as soon as it is fully developed
but waits until it senses the presence of a host. The main stimulus for emergence is the
vibration caused by the host's footsteps. This quiescent stage can be as long as 200 days
and explains why people entering deserted houses can suddenly find themselves covered in
fleas. In the time that the house has been deserted, the larvae have all pupated, only to
emerge when they sense the entry of the unsuspecting person.
Some women complain bitterly that fleas seem to be particularly fond of them. Wives
sometimes find themselves covered in bites after a night's sleep, while their husbands are
unscathed. The reason for this seems to be that fleas respond to female hormone levels.
For instance, the rabbit flea has been found to coordinate its life cycle with that of the
mother rabbit by sensing and responding to her hormones.
The medical importance of fleas goes far beyond the bites they cause as they are
important transmitters of disease, in particular bubonic plague. But the relationship
between fleas, bubonic plague and people is a story in itself and does not concern us
here, as the cat flea does not transmit this disease. However, the cat flea is an
intermediate host of the dog tapeworm, Dipylidium caninum, and one can become
infected by this worm if one accidentally swallows a flea.
Control of fleas
So, now that you know the life cycle of the flea, the way to stop fleas from becoming a
serious problem in your home is readily apparent. Don't let your cats and dogs sleep in
bedrooms and preferably make them sleep outside. Vacuum the floors and carpets regularly.
Clean your pets' bedding frequently, as it is here that most of the flea larvae will be
found. Dogs need to be washed fairly often (ask your vet for details), particularly the
older individuals who tend not to clean themselves thoroughly. There are a number of
insecticidal formulations for controlling fleas on your pets and, once again it is best to
ask your vet for advice. If fleas in your house get totally out of control, it might be
necessary to fumigate certain rooms.
Rust, M.K. & Dryden, M.W. 1997. The biology, ecology,
and management of the cat flea. Annual Review of Entomology 42: