Vaginitis is a fictional condition featured in the Season Six episode, "Fun with Veal". The disease occurs when someone stops eating meat, and which causes its victim to break out in vaginas all over his body.
Stan Marsh develops Vaginitis in this episode after he and his friends steal Farmer Carl Denkins's baby cows preventing him from turning them into veal. During the stand-off with the police Stan quit eating meat for a few days.
According to Dr. Doctor, if he had stopped eating meat completely, he would've turned into one giant pussy. This could be a reference to the fact that Eric Cartman said that only pussies don't eat meat.