I heard of these stupid people videos of people and animals mating.?

i heard o this stuff yesturday lol. i know its stupid and gross. i heard of girls doing it with dogs, boys with cows goats dogs and all. so i have a question, dont they get any disees or sickness if they do it? epesially if a boy has $ex with a cow, will he get any sickness? is it curable?