Several flea species infest household pets and domestic animals. The dog flea and the cat flea are two of the most common species, both of which are parasites also on human beings, poultry, and livestock. The human flea, the species frequently found most on people, is distributed throughout the world, but is uncommon in the United States. The dog flea, cat flea, and human flea are all intermediate hosts of the dog tapeworm. Tapeworm eggs are deposited in fecal matter, and some of these eggs may cling to the hair of the primary host.
Fleas swallow the eggs, which then undergo some development in the flea.
If an animal or person accidentally swallows an infected flea, an adult tapeworm develops in the new host. The rat fleas, in the Tropics and in Europe, are important carriers of bubonic plague. The sticktight flea is another common pest, noted for its habit of clinging tenaciously to its host. Dog eczema is usually associated with the presence of fleas. Fleas are controlled by destroying the adults and making breeding places unsuitable for larval life.