This post adds indirect evidence that histoplasma capsulatum plays a role in the aetiology of PD. However, the case remains inconclusive.

Start with the maps by Willis et al. [1]

Parkinson's incidence: http://www.ncbi.nlm.nih.gov/pmc/arti...395/figure/F2/

Parkinson's prevalence: http://www.ncbi.nlm.nih.gov/pmc/arti...395/figure/F1/

Compare with the map by Rosahn showing the wintering areas of the European Starling [2]: http://icwdm.org/handbook/birds/EuropeanStarlings.asp

There appears to be a correlation between the maps.

Is there causality? Not directly, but possibly, as described before, via histoplasma capsulatum which grows in the birds' droppings [2], or by other pathogens in the faeces such as E. coli, salmonella, mycobacterium avium subsp paratuberculosis [3].

References

[1] "Geographic and Ethnic Variation in Parkinson Disease: A Population-Based Study of US Medicare Beneficiaries"
Allison Wright Willis, Bradley A. Evanoff, Min Lian, Susan R. Criswell, and Brad A. Racette
Neuroepidemiology. 2010 April; 34(3); 143-151.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2865395/

[2] http://icwdm.org/handbook/birds/EuropeanStarlings.asp

[3] "Escherichia coli, Salmonella, and Mycobacterium avium subsp. paratuberculosis in wild European starlings at a Kansas cattle feedlot."
Gaukler SM, Linz GM, Sherwood JS, Dyer NW, Bleier WJ, Wannemuehler YM, Nolan LK, Logue CM.
Avian Dis., 2009, Dec; 53(4);544-51
http://www.ncbi.nlm.nih.gov/pubmed/20095155

John