Pediculosis is an attack or subsistence on the skin by small, wingless parasitic insects, commonly known as lice. While infestation with fleas and ticks may be common, infestations with lice are usually rare on dogs, and are often associated with dogs debilitated by disease, age or neglect, on which burdens may become exceedingly large. Lice are spread by direct contact or by contaminated brushes, combs, and bedding. Canine pediculosis is usually caused by Trichodectes canis biting lice, Heterodoxus spiniger biting lice, or Linognathus setosus sucking lice. Linognathus setosus sucking lice have mouthparts adapted for sucking blood. With heavy infestation, they produce sufficient anemia to cause weakness, and some animals become distraught and ill-tempered because of the chronic skin irritation. Sucking lice do not move and are easily seen and caught.2 They usually feed in the neck or shoulder region. Trichodectes canis and Heterodoxus spiniger lice feed on skin debris and hair, but some species have also mouthparts adapted for drawing blood from their hosts. Biting lice move rapidly and may be difficult to find and capture. Because they are active, they may cause more irritation than sucking lice, and rubbing by their host can cause severe alopecia. Trichodectes canis is the common biting louse of dogs and may act as the intermediate host of the dog tapeworm.2

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Body lice are capable of transmitting important bacterial pathogens.

Lice produce few lesions, but secondary dermatitis from scratching may be severe. Pediculosis may look like flea allergy dermatitis.2 Clinical signs are variable. Some animals can have no clinical signs and be parasite carriers. In others, there may be minor skin inflammation only, alopecia only, pimples and crusting eruptions, anemia, weight loss and intense itch.1 Lice usually accumulate under mats of hair and around the ears and body openings. To treat pediculosis parasiticidal dips, powders or shampoos are used once weekly for 4 weeks. Frontline flea spray is applied twice 2 weeks apart to kill adult lice. Ivermectin may be prescribed for sucking lice as for cheyletiellosis. K9 Advantix II (imidacloprid, permethrin, and pyriproxyfen combination) kills biting lice. The premises must be cleaned up thoroughly. Wash bedding, brushes, and combs, treat all affected dogs and those animals in close association with them.

Pediculus humanus, human louse
Photo source: National Science Foundation


  1. Scott, Miller, Griffin. Parasitic Skin Diseases
  2. George H. Muller, Danny W. Scott, Robert Warren Kirk, William Howard Miller, Craig E. Griffin. Muller & Kirk's Small Animal Dermatology

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