Yes, ANTHRAX is a Scrabble word!

Letter values in Scrabble US: A 1, N 1, T 1, H 4, R 1, A 1, X 8.

Is it a valid word?

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

a highly infectious animal disease (especially cattle and sheep); it can be transmitted to people
a disease of humans that is not communicable; caused by infection with Bacillus anthracis followed by septicemia

Also: splenic fever.