Mad Cow-like diseases may spread through urine
The agent that causes mad cow disease, scrapie and chronic wasting disease in deer and elk may sometimes be spread through urine, Swiss researchers reported on Thursday. They found that, under certain conditions in mice, the deformed brain proteins known as prions that transmit the disease could be found in urine. "We tested whether chronic inflammatory kidney disorders would trigger excretion of prion infectivity into urine," Adriano Aguzzi of the University Hospital of Zurich and colleagues wrote in their report, published in the journal Science.
Scrapie-infected mice with kidney inflammation excreted prions in their urine, and these prions infected other mice with scrapie when injected, Aguzzi and colleagues found.
So we now have a new vector of transmission -- one which can potentially encompass all the cows that graze on a particular area.
In practice, you'd need a ton of mouse urine all over your cattle feed to infect the cattle. It takes a fair amount of determination to infect something with a prion condition. Unfortunately, the practice of feeding animal meal to livestock is exactly the "right" method to ensure continuous bombardment of the livestock with infectious prions.
I'm not really worried about this mode of transmission yet, unless prion infectivity spikes massively. The big problem is still "feeding herbivores to other herbivores" and failure to screen effectively for BSE.