Field Guide to Venomous and Medically Important Invertebrates ...

cosmopolitan distributions, can be very annoying pests of people. Cat fleas are typically more
locally abundant and generally distributed than dog fleas. These fleas attack a wide variety of
other mammals such as foxes, raccoons, and rats. When populations are large, cat and dog fleas
can inflict numerous bites that may develop into dermatitis, which requires treatment with topical
corticosteroids or systemic antihistamines. The female fleas lay their eggs among the hairs of
these animals and the eggs drop off onto the mat or rug where the pets sleep or rest, onto carpets
and overstuffed furniture, cellar floors, and similar places. Larval development usually requires
at least two to three weeks, and the newly emerged fleas simply hop onto cats or dogs as they
walk by. However, if people leave their homes and take their pets with them, or board their cats
and dogs at an animal hospital for two to four weeks or longer, an enormous number of adult
fleas may reach maturity in a vacant house or apartment. These fleas have had no opportunity
for a blood meal, and when people return to their homes, they may be attacked by hundreds of
hungry fleas. In the summer, cat and dog fleas will breed outdoors in vacant lots, under houses,
in barns, and similar locations, particularly if there are stray dogs or cats about. The human flea
(Pulex irritans) occasionally becomes abundant on farms, particularly in abandoned pigpens.
The human flea is distributed throughout the warmer parts of the world. It is the most important
species attacking man on the Pacific Coast and is often responsible for a dermatitis or allergy due
to flea bites. The human flea attacks a wide variety of hosts including swine, dogs, coyotes,
prairie dogs, ground squirrels, and burrowing owls. Human fleas has been experimentally
infected with plague and shown to be capable of transmitting the bacteria in the laboratory. A
related species, Pulex simulans, occurs in central and southwestern United States and in Central
and South America. Some previous records of Pulex irritans probably refer to this second
species.