From Nature.com an article from the Journal of anti-biotics, an article that covers the development and origin Avermectin, Ivermectin, Stromectol, also the original application and evolution to possibly treat a myriad of diseases read/browse to the end. 

"That horse paste is pretty amazing stuff, especially the version for humans, prolly saved millions since the 80's but still not entirely eliminated, parasites are everywhere, don't drink river water." says jarasan.

here is article:

https://www.nature.com/articles/ja201711