Lice are wingless insects that spend their entire life cycle on the host and are spread to other hosts via direct contact. Typically, they only parasitize one species of animal.
Lice come in two varieties: sucking or biting lice. Sucking lice move very slowly and have pointed, piercing mouthparts for feeding. In North America, Linognathus setosus, is the one species affecting dogs. Biting lice are smaller than sucking lice, move much more rapidly, and have a more rounded head and biting mouthparts. The biting lice of dogs include Trichodectes canis and Heterodoxus spiniger.
Female lice attach their eggs (nits) to the hairs of the host. Lice infestation is typically diagnosed by identification of adults and nits on the affected dog. The nits are quite resistant to most insecticidal chemicals.
Lice have poor survival capability when off the host.
Typical signs of lice infestation include:
Treatment involves the use of insecticides. Since the nits are quite resistant to most insecticides, a repeat treatment after an interval of several weeks is indicated to kill young lice that may have hatched.