Pondering Post-Naturalism: Part Two

In one of my recent posts, I discussed the notion of post-naturalism, the idea that "nature" is not inherently valuable for its own sake but rather for the value it provides humanity, be it for economic reasons or mere aesthetic pleasure. I personally think that this philosophy is not objectively "better" than naturalism, but it does leave open an interesting question: what to do with species that don't have any such value?
A classic case in point is the guinea worm of Africa. The guinea worm is a parasite that breeds exclusively in the bodies of humans, which it enters by being ingested along with water as a larva. The adult female guinea worm can grow up to thirty inches long, and can lay thousands of eggs. When she is ready to do so, she emerges from her host and releases them into the nearest source of fresh water. Infection with a guinea worm is rarely directly fatal, but it is extremely painful and can cause malnourishment and starvation. In the 1980s, former US president Jimmy Carter began a program to eradicate the guinea worm completely, and as of 2016 the species is believed to be near extinction.
But is this really a good thing? After all, the guinea worm is an animal that is being driven to extinction by humanity-- under the Endangered Species Act, it would seem logical to have it declared a threatened species and protected as such.
The problem with this, of course, is that the guinea worm, and other parasites like it, have no alternate hosts. They cannot live as they are and do otherwise. This is one of the biggest dilemmas of the environmental movement--where does one draw the line when protecting biodiversity. If one decides that a species deserves to be driven extinct simply because it is a "pest" with no redeeming value to humanity, this reopens some old wounds that the Endangered Species Act was designed to heal. Many now-extinct animals, like the thylacine (a wolflike marsupial from Tasmania), were killed off simply because they were seen as useless pests. Today, we consider them tragic losses.
How is the guinea worm any different?