I was looking into the fruit soursop, and ran across this website. Don't have much faith in the article but PSP was referred to as a "virus".
Once had a horse who appeared to have had a stoke. He seemed partially paralyzed on one side of his body. Dr. Andresen the veterinarian looked perplexed examining him. Going against the humane way of dealing with an animal in this condition, we decided to see how his condition played out naturally. About a week past my mom Called me up shouting, " That Dam Horse", I asked if he died, she responded "No, on the contrary he's running around rolling like a three year old!" Chris, short for Chrisma his name, was over 30 years old. Ended up being the first and oldest on record to contract the West Nile Virus and live.