I guess we should not confuse between parasitic type of white tongue and indigestion type of white tongue.
Parasitic and worms are caused by poor hygiene or eating uncooked food or eating food with dirty hands. I strongly recommend that people should have good hygiene. Also if people have parasitic infection, I strongly advise them to go to hospital to check it out because this is not simple matter. If one has parasitic infection, that person should look awful not just only on the tongue but on the appearance of the face too.