lice

Wrasse fish are used to keep farmed species such as salmon free from sea lice and helps minimise the use of chemical treatments.

There are also long-standing concerns around parasitic sea lice and the use of chemical treatments in open waters.

During the last thousand years, the first of these transformative cataclysms was certainly the Black Death of 1350, one of history’s greatest waves of mass mortality via disease, this one spread by rats carrying infected lice from Central Asia across Europe.

“It just doesn’t make sense, if you think about the life cycle of the lice, to send a kid immediately home when you see it, when it's very likely possible that they've already been infected for three weeks or so,” Lena van der List, a general pediatrician from the University of California-Davis Children's Hospital, told Salon in a phone interview.

When people think they're seeing lice, van der List said, they are just casings of these nits that aren’t alive.