I found this recent article to be very interesting. The focus of the article is on Alzheimer's (in fact it never mentions PD), but what struck me was the possible relevance to PD of much of what was said.

Could pathogen infection really lead to Alzheimer’s?

I've wondered about this myself. But if PD is caused by an infection, why don't we see clusters of PD? Wouldn't people living in the same house, or those treating PWP, the doctors, nurses, caregivers, get it as well?

If PD is caused by a pathogen that isn't infectious in the traditional sense, so it doesn't spread from person to person like a cold, then how does it get in the brain? To test this out, it seems like it would be relatively easy to introduce a pathogen into a mouse brain and see if it lodged in the PD part of the brain. I'm not a scientist, though, so have no idea if that would even be possible.

lurkingforacure said: "... how does it get in the brain?"

Personally, I find the Braak staging hypothesis fairly convincing (i.e. PD starts in the olfactory bulb and the gut wall, and then travels via nerve fibres to the brain stem and beyond).

In this regard I found the following article very interesting. It discusses the case for the "travelling" being done by alpha-syn oligomers and fibrils, rather then by traditional pathogens.

Pathology: The prion principle : Nature : Nature Research

Thanks for your link jeffreyn - it is interesting.

The idea that infectious agents may be significant in some cases of sporadic AD has been round for a while. There is a free-access discussion of this here Can Infections Cause Alzheimer's Disease? | Epidemiologic Reviews | Oxford Academic.

Dr Balin has focused on the possible role of Chlamydia pneumoniae infection in AD.

Some independent investigators have tried and failed to replicate some of his reported findings about this (see article above). It is curious that Dr Balin chose not to mention this in his opinion piece. I can only speculate about the reasons for this omission...

Overall, I would put this concept into the "interesting but unproven" basket - as the authors of the discussion above point out, a lot more work is needed before we know what is going on.

Thanks for your link kiwi33.

You said: "Some independent investigators have tried and failed to replicate some of his reported findings ..."

Yes, but the review article also says that some researchers did report similar results. As their concluding section states: "...studies have shown that certain infectious agents, such as HSV-1 and C. pneumoniae, can induce AD neuropathologic changes in vitro and in vivo."

And as Balin himself says in the interview: "Not enough neuropathologists understand how these types of organisms can promote inflammation and the generation of amyloid and/or tau pathology even though we and many others have demonstrated this experimentally after finding these organisms in human AD brains."

I also note that the review article was accepted for publication in 2012, and that the Balin interview was published in 2017.

Overall though, I would agree that "a lot more work is needed before we know what is going on".

Here is another article on the theme of infection and Alzheimer's disease, but it's focus is quite different from the article with which I started this thread.

Once again though, as I was reading the article I wondered how much of what was said could apply to PD as well.

https://www.nytimes.com/2016/05/26/h...tion.html?_r=1

Many years ago I had very bad Lyme disease with emphasis on meningitis that lasted about a year. I often wonder if that was the precursor to my PD. And I imagine a bad fall from a horse when I was a kid around ten years old didn't help either. But back to my brain and a pathogen, I lost my sense of smell permanently during my Lyme. I am new to this forum. Thanks.