Quite a good overview of recent research reports on the possible role of the gut in PD:
Trying to digest gut research | The Science of Parkinson's disease
(hat tip to parkie13 at HU for the link)
Plus a recent open-access article on the possible role of intestinal inflammation in PD:
The gut-brain axis: is intestinal inflammation a silent driver of Parkinsons disease pathogenesis? | npj Parkinson'''s Disease
(hat tip to Blackfeather at HU for the link)