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768 Pediculosis

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PEDICULOSIS Louse nits attached to hairs on a black dog. (Courtesy Dr. Kinga
Gortel)

○ In dogs, secondary pyoderma and pyo- PEDICULOSIS Microscopic exam of dog hair with attached louse nit. (Courtesy
traumatic dermatitis (hot spots) Dr. Kinga Gortel.)
○ In cats, miliary dermatitis
• Occasionally, weakness, pale mucous mem- ○ Clear tape can be used to pick up parasites ○ Imidacloprid and imidacloprid + perme-
branes in puppies (sucking lice) and nits thrin spot-ons; labeled in some countries
○ Hair can be plucked or clipped from ○ Selamectin and fipronil spot-ons
Etiology and Pathophysiology suspected areas because nits are firmly ○ Various pyrethrin, carbamate, lime
• Infestation by insects of the suborder Ano- adhered to hairs. sulfur, and (for dogs only) permethrin
plura (sucking lice, which feed on blood) or • Hair and surface samples can be collected preparations
Mallophaga (chewing or biting lice, which using a flea comb and similarly examined. ○ Isoxazoline drugs: reports of success,
feed on skin debris and hair) anecdotal at this time
• Dogs: sucking louse Linognathus setosus and Advanced or Confirmatory Testing ○ Ivermectin is not recommended due to
chewing louse Trichodectes canis Response to therapy can be used but is not safety concerns.
• Cats: chewing louse Felicola subrostratus specific for pediculosis. • Follow-up is recommended to ensure com-
• Rarely, other louse species plete eradication of lice. Treatment failures
• Lice have a 2- to 3-week life cycle spent TREATMENT are sometimes seen.
entirely on the host and survive only a short • In weak, anemic puppies, additional sup-
period off host. Treatment Overview portive care (including blood transfusion)
• Lice may be capable of transmission of The goals of therapy are eradication of lice as needed
Bartonella and Rickettsia spp in some animals, from the patient and in-contact animals and
but their importance as vectors for dogs and amelioration of associated clinical signs. Recommended Monitoring
cats is not known. Recheck patients after 4-6 weeks.
• T. canis can act as the intermediate host of Acute General Treatment
the tapeworm, Dipylidium caninum. • Treat the affected pet and same-species, PROGNOSIS & OUTCOME
in-contact animals.
DIAGNOSIS • Wash the premises, bedding, collars, and The prognosis, with the exception of severely
grooming equipment at least once. anemic or debilitated animals, is excellent.
Diagnostic Overview • Clip matted hair.
The diagnosis is confirmed by finding lice or • Bathe the pet, unless debilitated, to remove PEARLS & CONSIDERATIONS
nits on physical and microscopic examination. lice.
• Treat secondary pyoderma (p. 851). Comments
Differential Diagnosis • Pruritus is reduced in 2-4 weeks. If severe, • Nits attached to hairs may be mistaken
• Other ectoparasite infestations, particularly consider extralabel coadministration of for skin scales but are of uniform size and
fleas, Sarcoptes, Cheyletiella antipruritic therapy such as oclacitinib almost impossible to remove from hair shafts.
• Various hypersensitivity disorders (adult dogs) or antiinflammatory doses of They are harder to see on light-colored
corticosteroids (dogs or cats). hair.
Initial Database • Lice succumb to many insecticidal agents. • Close examination with a good light source
Attempt to find and identify ectoparasites, Nits are more resistant, and repeated treat- is key.
including lice, in pruritic cats and dogs ment after 2-4 weeks is needed for products • Consider treatment trial if history is
(p. 1091). without residual efficacy. suggestive.
• Thorough direct examination of skin and • In many countries, imidacloprid-containing
hair can reveal lice and nits. This is aided products are labeled for canine pediculosis. Prevention
by adequate lighting and magnification (if Most other commonly used treatments are Because pets regularly receiving flea control
available). Suspect material is transferred to used extralabel. products are less likely to contract lice, pro-
microscope slide with a drop of mineral oil • Treatments considered effective for lice tection should be considered in lice-endemic
and examined at low magnification: include areas.

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