Though hygiene has little to do with pubic or head lice, body lice thrive in lower socioeconomic groups where clothes aren't frequently changed or washed. These mites are much tinier than lice, and you can't even spot them. Furthermore, they spend almost all of their lives burrowed into your skin. You'll usually find tracks in groups at the wrists, buttocks, underarms, groin, and especially the webs between the fingers. Scabies cause intense itching from the eggs and droppings they leave under your skin.
Prevention is strictly a matter of avoidance.
With the exception of body lice, bathing won't help much because soap won't kill lice or scabies, and they cling forcefully to the skin. Sharing clothing, beds and sleeping bags, and unfortunately toilet seats, all increase your risk of hosting these creatures. If you or your children have contact with someone who has lice or scabies, do a careful magnified inspection of the usual areas as described above. Don't be ashamed. Remember somebody else passed them to you, so you needn't feel dirty or that you're a neglectful parent.