The definition of terrorism is "inciting fear", not necessarily "kill thousands". A million people afraid if they caught BSE/cow madness is definitely hitting that definition, especially as the stuff can't be tested for... people exposed to prions will have that sword hanging over their neck for the rest of their lives, and the affected area will be out of order for years.

To this day, many countries ban all people who lived in the UK between 1980-1996 from donating blood (https://www.srf.ch/news/schweiz/bse-nachwirkungen-blut-spend...) simply because of that fear.