Foraging and Parasites: Are You In Danger When You Eat Wild Food?

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Many people enjoy picking wild blackberries – but are they in danger from parasites on the berries? Image by Brombaer CC BY-SA 2.0

Foraging for food in the wild is in. Let’s be honest; it’s never really been out. Nothing tastes more exotic than a tender spring fiddlehead cut by the river and steamed right away. Who wouldn’t reach for a plump ripe blackberry at the edge of the trail, or a low-hanging apple in the fall?  Recent interest in edible wild plants and wild meat has, however, made foraging fashionable.

Is foraging safe? Articles about foraging often focus on identification of wild plants, when to pick them, and what species to avoid. It’s true that whether or not a mushroom or green is poisonous is of more immediate concern than whether it might transmit a parasitic disease, but organisms like parasites rank high in food safety issues too.

Can We Catch Parasites From Foraged Foods?

Think back to the days before plant and animal domestication; our distant forebears were hunter-gatherers. They foraged for everything, and this was how they acquired most of their parasites (those that they weren’t sharing directly person to person, such as lice). Picking up parasites from contact with soil, drinking water, and the wild foods that they ate was the norm. Make no mistake, those parasites haven’t gone away; so far, science does not record any instance of a parasite infectious to humans going extinct.

If anything, we have made things worse. Domesticating crops and animals has given a lot of parasites unprecedented opportunities, but dense human populations, large numbers of domestic animals, and  our environmental impact have changed things in the wild as well. For example:

    • All surface waters, everywhere, should now be considered contaminated by intestinal protozoa of humans and cattle.
    • Human communities in North America support unusually high populations of raccoons, carriers of a deadly roundworm.
    • Roaming and feral house cat has contaminated soils worldwide with the protozoan Toxoplasma gondii.
    • Migrating humans have spread lots of parasites to places where they were formerly not found.

Where droppings from grazing animals wash into streams, liver fluke larvae can infest watercress. Image by Rosemary Drisdelle

Foraged Food and the Risk of Parasitic Diseases

While studies of the risk of parasitic disease faced by foragers as a group may be lacking, mountains of literature document the risks of eating and drinking, and even walking, in the wild. The risk you face while foraging for wild food depends a lot on what you’re looking for, and where you’re looking for it. Eating wild animals can be the source of diseases such as trichinosis, toxoplasmosis, and intestinal flukes and tapeworms. Plants may be contaminated with human or animal feces, or they may harbor larval forms of parasites. In some places, picking up a zoonosis – a disease of animals – is the major worry; in others, parasites of humans are more common.

In tropical developing countries, sanitation is often poor and fecal contamination of the environment intense. As Jared Diamond writes in Guns, Germs, and Steel, “Latrines are merely one of the places where we accidentally sow the seeds of wild plants that we eat.” Latrines are also good places to pick up parasitic infections; forage there at your peril. In the tropics as well, edible aquatic plants can transmit liver and intestinal flukes. In South America, making a sweet smoothie with foraged sugar cane might get you a nasty case of Chagas disease, caused by a parasite called Trypanosoma cruzi.

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