battle lines shift in the war against lice

Think your plate is full? If you're an elementary school teacher, you have a unique teacherly task: catching lice before they're catching. And now it seems that lice populations are evolving resistance to a common countermeasure.

Eighty per cent of head lice appear resistant to a common treatment that relies on pyrethroid chemicals, researchers report.... Parents should try products containing organophosphates or silicone-based insecticides as a first-line approach to rid their children’s hair of the bugs, according to the new study.

Thankfully, it's been reported only in Wales and Israel so far, but scientists warn that the problem may grow.

There's a metaphor in here. Something about developing new strategies to persist in the face of opposition. Maybe we've got to be the nagging itch in the district's scalp.

I didn't say it was a good metaphor.