Fleas and Flea Control
August, 1996
Every dog has had the experience of dealing with the flea, an
ubiquitous tiny pest that can create big problems. Over 90
percent of the fleas found on dogs are actually the “cat
flea,” tenocephalides felis. They prefer to parasitize cats
and dogs, but will live on any warm-blooded animal. Adult fleas
spend nearly all their time on their host and the pre-adult forms
are mostly found in the environment.
The eggs are produced while the flea is still on the dog, but,
because they’re not sticky, they fall into the environment.
Temperature and humidity are important to the flea’s
development and its timing. Optimum levels are 70 - 80 percent
humidity and 70 - 90 degrees Fahrenheit. The eggs hatch into
larvae, which resemble tiny caterpillars, in 1 - 10 days. Newly
hatched larvae are drawn to dark, protected areas, where they
feed on organic debris and adult flea feces. The larva stage is
complete in 5 - 11 days. During that time, they are very
susceptible to dryness, high heat and extreme cold. The larva
produces a silk-like cocoon, which houses the next phase, the
pupa. The cocoon protects this stage from extremes in temperature
and humidity, and all insecticides. It is in this stage that
fleas live over the winter in colder climates. Adult fleas can
begin to emerge from their cocoons in as little as five days,
under ideal conditions. The actual emergence is stimulated by
warmth and vibration, such as an appropriate host (animal or
person) passing by. Without the proper stimulus, the cocoon can
remain intact for about 140 days. In most households it takes
three to four weeks to complete a life cycle. Outdoors, if
conditions are less than ideal, it may take a few months.
A female flea starts producing eggs three to four days after her
first blood meal. She averages 20 eggs per day. Under
environmental conditions that allow a 21 day life cycle, a single
female can be responsible for an infestation of more than 20,000
adult fleas and 160,000 pre-adults (eggs, larvae and pupae) in 60
days!
Flea saliva contains a variety of substances that can be
irritating or allergenic. The severity of the itch depends on the
number of fleas present, the tolerance of the dog to skin
irritation and, most importantly, if the dog has developed a true
allergy to flea saliva. In addition to skin damage caused by
scratching, licking and biting, and by secondary bacterial
infection, a heavy flea infestation can cause anemia through
blood loss, especially in small puppies. Fleas are also
intermediate host for one species of tapeworm. They carry the
infective stage of Dipylidium caninum, so that when the dog
grooms himself and swallows a flea, adult tapeworm can develop in
the small intestine.
A good flea control program is one that affects all stages of the
life cycle, and usually requires treatment of the environment and
all animals that may act as hosts. However, for the hunting dog,
their environment includes the area they hunt. Because treatment
of that area is impossible, hunting dogs will undoubtedly pick up
fleas. One can, however, treat all other areas the dog inhabits.
This may include the house, the yard, kennel or dog coop. Because
larvae require dark, protected areas, adults will not develop
from eggs that fall on paved surfaces, or short-cut, sun-exposed
lawns. They can develop in the dog’s bedding or in tall
vegetation.
Pesticides registered for outdoor use come in powder, liquid or
granular formations and frequently contain chemicals from the
more toxic classes of insecticides, either carbamates or
organophosphates. Recently a new biopesticide system has been
marketed (InterruptVeterinary Product Laboratories). This product
contains nematodes - harmless, soil dwelling organisms that feed
on flea larvae and pupae. It is non-toxic to humans and animal,
but its effectiveness is not yet known.
A future article will discuss treatment of the indoor environment
and the dog itself.