. . that eat plankton that grow up on city effluent and storm runoff (with plenty of nutritious crank case oil)?

Remember, the oceans are a desert - the marine food chain is almost completely dependent on nutrients washed down from the land.

Now, on a more cheerful note - experiments in the agriculture colleges have shown other advantages of "integrated farming".

By building a drying line between the egg production barn and the cattle barn, expensive cattle feed can be cut about 30% with chicken droppings before the cows object, and chicken droppings are nearly as nutritious as the regular feed. The ratio can be increased even higher if the mix is further cut with styrofoam beads.

Then you haul the cow byproducts out and spread them on the fields to grow more chicken feed.

I don't know if any farms are actually using this system yet, but it has been seriously proposed.

Nematodes (parasitic worms) sometimes attach to the stomach lining or penetrate the intestinal wall causing painful illness. They find humans a hostile environment and are usually dead within 10 days.

Tapeworms can be with you for years and years. Alaskan wild salmon are notable carriers of tapeworm larvae.

All these worms are most often contracted from salmon sushi but sometimes from undercooked salmon. They are killed by temperatures of 140°F and above.

Bon appétit.

Steralized slaughterhouse waste would be among the cow byproducts used as furtilizer to grow chicken feed. It has to be disposed of somehow, and this way it doesn't get back to the cows until it's already been a plant and through a chicken. Chickens are not generally thought to transmit bovine diseases.

Of course the general public would probably rather not know the cow made the milk they're pouring on their breakfast cerial out of chicken droppings, but hey, there's a lot of things they'd rather not know.

Plants can still use the nutrients even after incineration temperatures, animals can't - and I doubt any prions would be incorporated into plant tissue in any case, but you'd have to be careful if land was fertilized with material containing prions.

Prions can be destroyed by temperatures significantly above normal sterilization (above 140°C/280°F) and by chlorine or lye.

California poultery growers are really into contamination elimination right now. They're using techniques more frequently associated with electronic clean rooms and employees are forbidden to have pet birds.