> Perhaps because we have probably already discovered pretty much every parasite that infects humans, at least those with widespread impact in the western world?
The thing is, discovering them is not enough, not by far. We know how to avoid a few of them - say, by washing hands, regulatory agencies requiring meat be controlled for parasites (in Germany and possibly EU, against trichinella [1]), or by heavily suggesting pregnant people not handle cat litter (to prevent toxoplasmosis). We know how to treat a few of them (mostly worms).
But we don't know how to treat a lot of them, for some of them (particularly in the veterinarian world) we're dealing with resistency developing. And a few of them remain utterly and completely deadly (Naegleria fowleri).
The problem is, as always, a lack of funding. No one wants to spend much money on parasitology (as you said: we know about most of them), and since most parasitic infections are rare in Western countries that have the money, there is not much money for treatment R&D - no matter how many people die each year worldwide (400k for worms, 600k for malaria alone).
Malaria in particular is a target of constant attention. Latest breeds of generically modified mosquitoes are unable to carry the disease [1] or that turn the carried mosquito populations infertile [2]. I'd say that malaria will be eradicated in 30-50 years. Hopefully, Guinea worm will be eradicated, too [3].
Neither malaria nor Guinea worm affect "Western" (rich, industrial) countries directly, but people from these countries most actively work on the eradication, chiefly financed by charitable funds.
The thing is, discovering them is not enough, not by far. We know how to avoid a few of them - say, by washing hands, regulatory agencies requiring meat be controlled for parasites (in Germany and possibly EU, against trichinella [1]), or by heavily suggesting pregnant people not handle cat litter (to prevent toxoplasmosis). We know how to treat a few of them (mostly worms).
But we don't know how to treat a lot of them, for some of them (particularly in the veterinarian world) we're dealing with resistency developing. And a few of them remain utterly and completely deadly (Naegleria fowleri).
The problem is, as always, a lack of funding. No one wants to spend much money on parasitology (as you said: we know about most of them), and since most parasitic infections are rare in Western countries that have the money, there is not much money for treatment R&D - no matter how many people die each year worldwide (400k for worms, 600k for malaria alone).
[1] https://de.wikipedia.org/wiki/Trichinenuntersuchung