We do not share parasites with cattle and chickens. We DO share parasites with pigs. I STILL cook my pork long enough to kill a tapeworm.
Here's the deal, a parasite needs a host to survive. The worm sheds eggs which leave the herbivore via the feces. Survival depends upon being eaten on the grass by another host herbivore. When it is dry, whether hot or cold, the eggs die. We horse owners try to remove their poo and pile it up, which heats the eggs and kills them. Droughts also kill them. Dewormers kill them best of all, but every horse still carries a small parasite load. Some are more resistant than others. Generally "hard keepers", horses that have a hard time keeping weight on, are less resistant to parasites, for the most part. I am NOT an expert on this, but the horse community has gone to have fecal samples tested for #'s of parasites. We don't deworm these horses as often as those with less resistance.
Point being, by the time you use cow manure the eggs are dead and you will not injest them.
I grew up and lived in Cal. Central Valley where much of our country's vegetables and fruit is grown. I own a 20 acre ranch there. Every year I hire a couple migrant workers to hoe weeds in the pastures and along fencelines . I tell them that if they have to go, just come to the house to use the bathroom. But , instead, they just urinate when and where they happen to be. 
There are field crops and orchards all around my ranch. During the times when the farmers need labor help, they provide porta potties for the migrant workers, but I see many of the workers relieve themselves wherever they happen to be. (Why walk a 100 yards to the porta potties ). When the Vet Nam immigrants came to Fresno, most live in apartments in town. Many of them lease an acre or more outside of town so that they can grow their vegetables for their family use and for sale at roadside stands or sell to local grocers. Many also grow strawberries for sale at roadside stands and grocery stores. This is a family venture and their entire families including their children work the crops. Where do you think that they go when the need arises ? In Cal., coyotes, Jack rabbits, ground squirrels, field mice, rats, black bird flocks numbering in the thousands , insects, etc. outnumber the human population several times over, so guess where they go when they dine on the crops ? 
I am surprised that more people are not sickened, more often. 
