Fleas are usually brown but their larvas are white. They are major source of spreading tapeworms. So there are more chances of fleas on it than any other disease. Try to clean its scab by gentle rubbing. If it comes off automatically then there is nothing to worry about. The best way to get rid of such diseases is to keep it clean. Give it bath regularly to keep it away from fleas.
Outdoor Cat Has Scabs On Head,neck. I Pulled One Off And Under It Was Like White Stiff Piece Of Thread. Could This Be From Flea Bites?
What kind of a vet tells people that bathing a cat will get rid of fleas? That's nonsense, it needs medication. Why are you pulling scabs off your cat? Let it heal.