I didn’t realize so many Monarch butterflies are infected with the parasite Ophryocystis elektroscirrha (OE), until I read this article about this phenomenon. There doesn’t seem much one can do about this problem. In the past some monarch breeding groups have stopped selling monarchs because of problems with sending out infected butterflies. You really need a good microscope to even see the spores. I noticed that Monarch Watch is again selling monarch larvae and I believe they are testing these larvae before they are sent out. If you’d like to learn more about this parasite checkout the MonarchParasites.org website.