Yes, LOUSES is a Scrabble word!

Letter values in Scrabble US: L 1, O 1, U 1, S 1, E 1, S 1.

Is it a valid word?

LOUSES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

wingless usually flattened bloodsucking insect parasitic on warm-blooded animals
a person who has a nasty or unethical character undeserving of respect
any of several small insects especially aphids that feed by sucking the juices from plants
wingless insect with mouth parts adapted for biting; mostly parasitic on birds

Also: sucking louse, dirt ball, plant louse, bird louse, biting louse.