Very informative site about roundworms:  http://www.innvista.com/HEALTH/microbes/parasite/round.htm

Even more roundworms info, with a graphic:  http://www.dr-dan.com/roundwor.htm

Ok, roundworms, IN HUMANS:   http://marvistavet.com/html/body_roundworms_in_humans.html

Benefits of animal waste collection on water supplies:  http://www.stormwatercenter.net/Pollution_Prevention_Factsheets/AnimalWasteCollection.htm