In case you aren't aware, horse de-worming is just one use of ivermectin. The fact that it's used for that doesn't make it merely a horse de-wormer.
> Ivermectin is an antiparasitic drug. After its discovery in 1975, its first uses were in veterinary medicine to prevent and treat heartworm and acariasis. Approved for human use in 1987, it is used to treat infestations including head lice, scabies, river blindness (onchocerciasis), strongyloidiasis, trichuriasis, ascariasis and lymphatic filariasis. It works through many mechanisms to kill the targeted parasites, and can be taken by mouth, or applied to the skin for external infestations.] It belongs to the avermectin family of medications.
Ivermectin is also used to treat COVID in countries that have endemic parasite outbreaks. COVID responds well to steroids, but so do parasites. Giving steroids to someone with parasites causes the parasites to become much stronger, and trigger reactions from the immune system: fever, etc.
I ideally you could test for parasites, but time and resources don't allow for that in many countries. So if it's generally safe to just give ivermectin along with steroids when treating COVID - in countries where parasites are common.
Maybe I'm wrong about this. Maybe I'm making it up. Don't listen to what I say. Listen to your doctor.