"They damaged his nervous system with a wartime Russian mycotoxin."

Mold
Creative Commons AttributionMold - Credit: psyberartist, Flickr
 Mycotoxins are poisons produced by fungal molds. They can be found on dead leaves, stored grains and compost piles.

Russia became interested in using T-2 mycotoxin as a weapon after witnessing the fatalities resulting from bread made with mouldy wheat during World War 2. T-2 has been suggested as a cause of Gulf War Syndrome.  For a time it was believed that T-2 had been used in Vietnam, when sticky "yellow rain" fell, although this is now thought to have been honeybee faeces.