If a greyhound gets lungworm it probably wouldn't matter if treated but if a working dog that needs to perform for longer periods gets it as it messes up there lung then it could mean early retirement death if not treated..I had 2 dogs get it one was ok after treatment and rest the other wasn't the same, my bitches throat swelled up it causes more bleeding to minor cuts or bruising they go blood shot in the whites of there eyes no stamina cough blocked nose.. I use advocate now panacur good to I used it for pups and I put copper take around stainless bowl I got told they won't go on it better