In general, pets cannot contract head lice from humans. Lice are species-specific, meaning lice that infect only humans cannot infect dogs or cats, and vice versa.
Lice bodies are adapted to specific hair widths, which is why there are species of lice that affect different parts of the human body. Pets that are suspected of harboring head lice should be taken to a veterinarian for diagnosis and treatment. Just as the lice themselves are species-specific, so are the treatments. In general, lice are easier to treat than fleas or other parasites, and a vet can recommend the proper course of treatment.