In reading about this affliction, the first thing that came to mind was poisoning by industrial chemicals.
I recently read the book, The Poisoners Handbook. It is about chemistry and the development of forensic medecine in New York City during the Prohibition years. Very interesting read.
That was the prevailing opinion, albeit agricultural chemicals. But, some additional research has been done and a study is about to be published that proposes an alternative theory.
Is it conclusive? I don't think so. But, discounting it simply because the "consensus" pins the blame on agricultural chemicals is like saying that "anthropogenic climate change" is "settled science".