That is interesting, although I'm not seeing the comment you're referencing. I read the article this morning, but I hadn't noted that there were possibly multiple types of screw worm. Looks like the Cochliomyia hominivorax is only one that the Americas typically have to deal with, so that was the only one that made sense in the context. However, that a anti-parasitic is more effective at killing one type of screw worm than another doesn't mean much by itself. That statement would hold true even if it had 99% efficacy against one type vs 98% efficacy against another.