Sure, we’ll save this species:
Not only do we not try to save the latter, we’re actively trying to wipe it out.
A recent article notes that one of the effects of breeding endangered species in captivity is that organisms that live on them can suffer. The black footed ferret (top picture) had a louse species specific to it that is probably gone forever. The same holds true for the California condors (second picture from top) bred in captivity, then released into the wild. The captive-bred animals were, perhaps, too healthy... from a certain point of view. Lice that lived on the condor were removed systematically, and as far as we know, that species is now extinct. These do not appear to be the only examples.
Those cases might be unintended consequences. It is possible that the people involved did not know about the parasites that lived on those species, and may have though they were general parasites, rather than ones that specifically lived on those species.
But it raises an interesting ethical issue about how much we value living species.
The third picture in my series is Dracunculus medinensis, also known as the Guinea worm. The Carter Center, founded by former American president Jimmy Carter, is spearheading a campaign to eradicate this species. Admittedly, Guinea worm is a human parasite that has caused a lot of misery to a lot of people over the millennia. Nevertheless, it is as irreplaceable a life form as much as a ferret or a condor.
I have never heard anyone suggesting that we might want to consider saving this species.
I can see the case for wiping out this species if it was an obligate human parasite, and there was no other way for this thing to live than infect human beings. But Muller (1972) showed decades ago that this species can be reared in captivity, in a non-human host. Some sources suggest it has a fairly wide host range (but haven’t been able to confirm that with peer-reviewed journal article yet).
If you think that conservation of biodiversity is a good thing, should someone start a Guinea worm captive breeding program? The goal might not be to reintroduce the species into the wild, given the harm it causes. Instead, the goal could to preserve it in perpetuity, both for scientific research and because of its intrinsic worth as part of the life on our planet.
Maybe we should have a parasite bank to go next to our seed banks.
Additional: Parasitologist Mark Siddall calls the expected loss of the Guinea worm something to celebrate in this New Yorker article. Mark and I tweeted back and forth on this quite a bit, and I am glad to have his article, with a personal touch, as a counterpoint to my little armchair essay.
Jørgensen D. Conservation implications of parasite co-reintroduction. Conservation Biology: in press. http://dx.doi.org/10.1111/cobi.12421
Muller R. 1972. Maintenance of Dracunculus medinensis (L.) in the laboratory and observations on experimental infections. Parasitology 64(1): 107-116. http://dx.doi.org/10.1017/S0031182000044681
Save the parasites!
Conservation biology of parasites (Surprisingly thorough Wikipedia entry)
Carter Center Guinea worm eradication program
Which endangered species would you save?
More harm than good intentions
No wildlife charity campaigns to save parasites. But they should (Added 9 February 2017)
Ferret picture by USFWS Mountain-Prairie on Flickr; condor picture by Pacific Southwest Region on Flickr; both used under a Creative Commons license. Guinea worm picture from Wikipedia.