Lice (Pediculosis)
Drs. Foster & Smith, Inc.
Race Foster, DVM

Lice are insects that can be seen with the naked eye. They are flattened and possess no wings. They are very host-specific and do not tend to leave their preferred animal, in this case dogs and puppies. Lice spend their entire life cycle on the pet. There are several kinds of lice. Blood-sucking lice belong to the group Anoplura. Those that do not suck blood, but rather chew skin, are grouped as Mallophaga.

Transmission of lice is by direct contact with an infested pet. Unlike fleas and ticks, lice do not persist or travel in the environment. Grooming instruments may, however, serve as a source of transmission.

Lice lay eggs (termed nits) on the hair shafts. The life cycle takes about 21 days to complete.

Trichodectes canis is the biting louse of dogs. Another commonly found biting louse of the canine is Heterodoxus spiniger. The only sucking louse of the dog is Linognathus setosus. Cats have one biting louse and that is Felicola subrostratus. None of these lice present a problem to humans.

What are the symptoms?

The most noted sign of a louse infestation is a scruffy, dry hair coat. Hair loss may occur and the animal may itch, at times severely. In very heavy infestations of blood-sucking lice (biting), one may detect anemia, especially in puppies. A diagnosis can usually be accomplished with the naked eye. Nits tend to be more visible than the actual louse, but both can be seen.

What is the management?

Of all the parasites of cats and dogs, lice are the easiest to eliminate, and they pose no threat to you or your children. Treatment is relatively simple. The dog may be bathed with a pyrethrin shampoo, and after the dog is thoroughly dry, a pyrethrin spray or powder can be applied. This treatment will need to be repeated in 10-14 days since all of the nits will not be killed. Alternatively, permethrins are also effective against lice. Do NOT use permethrins on cats. Another option is fipronil (Frontline), which has been approved for the treatment and control of lice in dogs. It usually is not necessary to treat the environment, but flea and tick foggers may help, especially in severe cases. Keep all grooming utensils clean.

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