I'm not recommending using drugs we don't understand or have a full picture of. I am recommending to stop calling it horse dewormer. At the very least call it an anti-parasitic in use in the 3rd and 2nd worlds.
I'm not a infectious diseases expert, but to my knowledge the viruses that it's been found to be effective against are all mosquito borne; it's just as likely related to it's toxic action on mosquitos in general. Still, it's all baseless conjecture on everyone's part. If someone cares to throw money at it, it's something that can be investigated.
At the end of the day just get the widely available vaccine and move on with life, like you would for other viruses that we've got vaccines for. I feel like we're all making this way harder than it has to be just so we can all continue to yell at each other.