In industrialized countries, wild plants are relatively safe as long as they are not contaminated with animal droppings (although, here too, aquatic plants such as watercress may transmit liver fluke). Pick with clean hands, leave anything questionable, and wash thoroughly. If you want to eat anything raw, wash it with running potable water.
Thorough cooking will kill just about everything, but be careful to clean surfaces that have come in contact with the uncooked food. Wild animals can carry nasty parasites in both meat and feces so, again, cook well and clean thoroughly (and don’t feed raw trimmings to the family dog).
Foraging for Parasites
No discussion of foraging and parasites is complete without noting that, in many cultures, people deliberately forage for parasites. Some fish, and shellfish such as oysters, are particularly tasty when infested with certain parasites; pea crabs, parasites of oysters are eaten as gourmet foods in North America. Robin Overstreet describes tasty caterpillars, nut-like botfly and warble fly larvae, fried “sweet meat” (liver flukes) from deer, and both fish and mammal tapeworms eaten raw, among other things. Thus, in the true spirit of foraging in the wild, when we come across a parasite, the first question is “will it hurt me?” and the second is “can I eat it?”
Roberts LS, and Janovy J. Foundations of Parasitology. (2009) Boston: McGraw Hill.
Overstreet, R. Flavor Buds and Other Delights. (2003) Journal of Parasitology 89:6, 1093-1107.
Diamond J. Guns, Germs, and Steel. (1997) New York: Norton. p. 117.
Decoding Science. One article at a time.