Chewing and Sucking Lice: Phthiraptera

The human body and head louse carries and spreads bacteria that cause the diseases louse-borne typhus, trench fever, and louse-borne relapsing fever. Louse infestations commonly occur among the homeless, or persons in refugee camps and other crowded conditions that result from war and natural disasters. Head lice are common among school children around the world. They are passed from one host to the next through infested clothing. Pubic lice, also known as "crabs," are normally spread through very close, personal contact by grownups.

Lice also infest domesticated mammals and poultry. Infested animals and louse control cost farmers and breeders hundreds of millions of dollars every year in lost production and the purchase of expensive chemical controls. For example, infested chickens will lay fewer eggs, resulting in less money earned by poultry farmers. Chemical pesticides are commonly used to kill lice on poultry and livestock. However, there are concerns over the safety of using these chemicals on large numbers of animals on a regular basis. There is also evidence that some lice are becoming resistant to pesticides. Louse resistance to pesticides was noted by the fact that fewer and fewer lice are killed with each application of the same amount of chemical.