Lice in dogs and cats: Trichodectes, Linognathus and Felicola
Shelter puppy with a dull coat, pruritus and numerous white specks firmly stuck to the hairs, which do not come off when blown. Under a magnifying glass, flattened wingless insects are seen moving slowly through the coat.
Regarding lice in dogs and cats, which statement is correct?
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A. Felicola subrostratus, the cat louse, is easily transmitted to people
Lice are highly host-specific: those of dogs and cats do not infest people, nor do human lice infest pets. It is not a zoonosis.
B. They require intensive, prolonged environmental treatment, like fleas
Lice complete their entire life cycle on the host and survive only a short time off it. Treating the animals and washing bedding, combs and grooming tools is enough.
C. Nits come off easily when brushing, unlike dandruff
It is the other way round: nits are cemented to the hair shaft and are hard to remove, whereas scales come off. That adherence is a useful diagnostic clue.
D. Trichodectes canis, the chewing louse of dogs, can act as an intermediate host for Dipylidium caninum
Correct. Like the flea, T. canis can harbour the cysticercoid of Dipylidium; treat the tapeworm if segments are present. Dogs also have a sucking louse (Linognathus setosus), which can cause anaemia in heavily infested puppies; cats have only one chewing louse, Felicola subrostratus.
lightbulb Key takeaway
Pediculosis is typical of young, malnourished or group-housed animals, or older cats that no longer groom. It responds well to the usual ectoparasiticides (fipronil, selamectin, isoxazolines); repeat or maintain treatment to cover nit hatching.
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Updated: October 31, 2026 · Educational content for veterinary professionals. It does not replace current clinical guidelines or the judgement of the attending veterinarian.