Lice are species-specific, meaning that they only live on their intended host animal. A dog louse must live on a dog. A human louse lives on humans. And so on. Lice cannot be passed from one species to another, but lice can be spread to other animals of the same species (i.e. human to human contact). Many species of lice are also region-specific, living only on certain areas of the body. Lice must live on the host animal. They can only live a short time off the host in bedding, clothing, etc.
Lice feed on blood, dead skin, feathers and sebaceous (oily) secretions; their diet is also species-specific. The first sign of lice infestation is usually itching. Lice eggs are also called nits, and are "cemented" to hair by the adult lice, which can make removal difficult. Special combs in addition to medications are useful for physically removing the lice eggs.
If you suspect that your child or pet has a lice infestation, please see your health care professional or veterinarian to properly diagnose and treat this condition.
Related Reading:
Can my pet catch head lice from my kids (or vice versa)?
References:
1Species of lice - Wikipedia: Louse

