Original article: https://www.nature.com/articles/s41467-025-63473-4

There is some evidence that the infecting agent (bacteria? prions?) travels from the gut to the brain along the vagus nerve.

https://pmc.ncbi.nlm.nih.gov/articles/PMC5440238/

Sorry am i reading this wrong or does it suggest the opposite?

>Conclusions: Although overall vagotomy was not associated the risk of PD, we found suggestive evidence for a potential protective effect of truncal, but not selective, vagotomy against PD development.

You're right that the article seems to be talking out of both sides of its mouth, so to speak, as to the effectiveness of vagus nerve surgery. But the paragraph that begins with "Gastrointestinal symptoms" seems to conclude that the vagus nerve does play a role in the disease.

Anecdotal but my dad had Parkinson's and prior poor dental history, so this interests me. My own teeth are better but no means perfect; based on this I'll have to pay scrupulous attention to hygiene and checkups, just in case.

Yes one more way our sugary diet is killing us.

Perhaps.

My grandfather had Parkinson's, despite living a very simple and plain life with an excellent (and calculated) diet.

I don't think they are suggesting that oral bacteria is the only cause of Parkinson's, but perhaps I misunderstood it.

was he exposed to Roundup?

Probably not specifically Roundup. He worked in rural electrification (farm stuff!) but was retired by the time Roundup became popular.

His parents were farmers, though, so there's no telling at this point what kinds of things (if any) he was around as he grew up.