Here is a great article on understanding Avian Bornavirus (ABV) and Proventricular Dilatation Disease (PDD) a.k.a. Macaw Wasting Disease, Wasting Syndrome and a few other names, a disease that is associated with feather picking and self-mutilation.

This is another study that was published in 2016 that may be useful to read through to remain up-to-date with the disease.