Save The Whales. Save The Tigers. Save The Tapeworms?

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Parasites play crucial roles in keeping ecosystems healthy, as does this larval trypanorhynch tapeworm, which infects fish.

Chelsea Wood

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Chelsea Wood

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A parasitic flatworm found in the bile duct of a swell shark.

Skylar Hopkins

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Skylar Hopkins

A parasitic flatworm found in the bile duct of a swell shark.

Skylar Hopkins

That worm depends on three different animals throughout its life, but some species can depend on even four or five.

«How does something so complicated evolve? asks Wood. «When you see how common it is across the parasite tree of life, you just have a lot of appreciation for the hurdles these organisms have to jump over just to complete one turn of the life cycle.

Wood and her colleagues found that as bird biodiversity declines, some parasite species also decline as a result.

«We think that about 1 in every 10 parasite species might be threatened with extinction in the next 50 years just from losing their habitat, says Colin Carlson, assistant professor and biologist at Georgetown University. «But when we account for that they might also lose their hosts, it pushes it closer to about 1 in every 3 species of parasite.

«That’s an extinction rate that’s almost unthinkable at broad scales, Carslon says.

Even though a host animal may be considered endangered, its parasites rarely are. Only a handful of parasite species are designated as endangered under the U.S. Endangered Species Act or the IUCN Red List of Threatened Species.

The parasite conservation plan recommends using those lists to protect the parasites that also depend on those endangered species.

«That’s not done right now, says Hopkins. «But it would be a really great way, really easy way, potentially, to get a lot of mileage for parasite conservation without necessarily devoting a ton of resources to parasite conservation.

To be clear, the plan doesn’t recommend protecting human parasites or those of domesticated animals. But for millions of others, it calls for new research, outreach and ensuring that parasites are included in conservation and restoration plans.

«Conservation often talks about this metaphor: If you pull the nails out of the side of an airplane one by one, how many can you take out before the plane can’t fly? says Carlson. «And we’re looking at that with parasites now. If we see the total collapse of parasitic ecosystems, we have no idea what that’s going to do.

Still, in terms of public support, parasites may have a long way to go.

«It is the wolves and the grizzlies and the polar bears — mostly the mammals — that really get people’s attention, says Jacob Malcom, director of the Center for Conservation Innovation at Defenders of Wildlife.

Still, Malcom says parasites deserve that attention too. Focusing on charismatic species can have the added benefit of protecting parasites and other animals at the same time. Preserving habitat for one central animal means it acts as an «umbrella species, simultaneously protecting an ecosystem for other organisms.

So, what are the chances that Defenders of Wildlife launches a «save the leeches campaign?

«It’s pretty close to zero, Malcom says.