This looks a lot like a fluke which include Gyrodactylus and Dactylogyrus. These are skin and gill parasites, not GI parasites. Alternatively, it could be one of the small worms that inhabit all tanks and collect on fish poop soon after it hits the tank bottom. It is not likely the cause of your fish's lack of appetite unless the skin or gills are heavily infected. A few of these on the skin or gills will not cause significant problems for the fish. You can youtube how to do skin scrapings and gill biopsies in order to rule out the possibility of disease from these. I applaud you for using a microscope, but to consider GI parasites, it is crucial to catch the poop before it hits the tank bottom. I know from personal experience that after it hits the bottom of the tank within minutes all manner of critters will start munching on the poop and it will be difficult to identify true parasites. See the Fish Doctor's brief comments and video of this:
https://www.youtube.com/watch?v=HHJ0nKIMvfg
I would encourage you to look for Cryptobia iubilans in fresh poop. I have posted several times on this and posted videos of it. There are also YouTube videos of Cryptobia. At the 2018 NADA meeting vet Dr. Stephen Smith stated Cryptobia was one of the most common, if not the most common, causes of chronic wasting disease in discus. It will not respond to Levamisole, Flubendazole, nor metronidazole.