I think I'm with the airline on this one but it's reported that they were unaware of the infection until en-route.
It is not uncommon for children to pick up headlice at school but they are easily treated.
Fox News elisabethmp2: I wouldn't want to be on a flight with this dirtbag and his filthy family!!
Headlice can be caught by anyone, clean or dirty.
Wiki:
About 6–12 million people, mainly children, are treated annually for head lice in the United States alone. High levels of louse infestations have also been reported from all over the world, including Australia, Denmark, France, Ireland, Israel, and Sweden. Head lice can live off the head, for example on soft furnishings such as pillow cases, on hairbrushes, or on coat hoods for up to 48 hours.