I agree, your thought process is very valid medically, and there are a number of medical articles that point to its possible use in humans infected with avian influenza. It looks like because it has jumped to humans in isolated cases, they are being forced into killing all exposed birds due to the mortality rate in humans. Depending on the article, the humans that got it had 35%-80% mortality. Remember that this is worldwide so many of the treating countries were not even close to real medical standards. So, though the Dept of Ag is not making big deal about the potential jump to humans, it looks like the real reason they are killing the birds, though they want to stop the spread in birds, is to prevent the virus from mutating to one that can easily be spread to humans, or heaven forbid, between humans. There are some articles says it has jumped to pigs in some cases. I seem to remember when it does this, it's much more likely to then be able to mutate and jump to humans. Of course to protect the food chain and mass starvation in many countries they want to prevent this jump too.Do you know if it has even been tested against Avian Influenza?
As I mentioned above, I realize that the viruses it has shown effective against are NOT AI but I'm betting it has never been tested (in chickens specifically). That could mean it COULD be effective and just hasn't been tested. Or maybe it's not at all, such as with Zika (in mice).
I'm just saying...aren't 2.75 million birds (and counting) worth giving it a try?
Source - https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7290143/
This article discusses the wide variety of viruses Ivermectin has been effective against. The first part of Table 1 shows all the viruses: https://mdpi-res.com/d_attachment/cells/cells-09-02100/article_deploy/cells-09-02100-v2.pdf