Grass plants bind, retain, uptake and transport infectious prions

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4449294/

"Prions bind to plants and bound-PrPSc efficiently sustain prion replication

Roots and leaves were washed thoroughly and analyzed for the presence of PrPSc by serial PMCA (Morales et al., 2012). The results show that even highly diluted PrPSc can bind to roots and leaves and sustain PrPC conversion (Fig. 1A). [...] However, both roots and leaves capture PrPSc efficiently, even at very small concentrations, equivalent to those present in biological fluids, such as blood and urine (Chen et al., 2010).

Animals can be infected by oral ingestion of prion-contaminated plants

After exposure, plants were extensively washed 5 times with water and animals fed with dried material orally. [...] All animals that ingested prion contaminated leaves and roots developed typical prion disease. Although the incubation times were significantly longer in animals ingesting prions attached to leaves and roots as compared with those fed directly with the brain material, the differences were not as high as one could have expected (Fig. 2A)."

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Something developed sporadic prion disease (in humans its called "Sporadic Creutzfeldt-Jakob disease": https://pubmed.ncbi.nlm.nih.gov/29887134/ ), died from it, plants grew on the fertilized land and were eaten by deer, the cycle repeats.

CWD-infected deer shred prions in urine, feces, probably saliva too (the aforementioned paper mentions that this is enough for plant-mediated infection), a trait shared with scrapie-infected sheep, hamsters and, i assume, BSE-infected cows.

Transmission and Detection of Prions in Feces

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2803675/

"Oral exposure to prion-tainted blood, urine, saliva and feces have been suggested as modes of transmission for CWD and scrapie among herbivores susceptible to these diseases. Both CWD and scrapie infection is thought likely to enter the body through gut-associated lymphoid tissues, in Peyer's patches in the alimentary tract. Moreover, the presence of the infectious isoform of the prion protein, designated PrPSc, in Peyer's patches suggests alimentary shedding of CWD and scrapie prions into feces. [...]

When noninfected Syrian hamsters were cohabitated with Syrian hamsters orally infected with Sc237 prions, we observed 80–100% infection rates within 14 days after oral challenge."

Also, birds can spread prions in their litter:

Crows don't digest prions, may transport them to other locations

https://www.sciencedaily.com/releases/2012/10/121017181250.h...

"Crows fed on prion-infected brains from mice can transmit these infectious agents in their feces and may play a role in the geographic spread of diseases caused by prions, such as chronic wasting disease or scrapie."