Poisoning food with feces is detailed as a tactic in the Al-Qaeda manual found a few years ago by British intelligence.
Also, there are precedents, both involving Muslims, as does this story:
“Man remanded after ‘urine’ attack,” from the BBC, May 19 (thanks to Jeff):
A man has been remanded in custody charged with spraying urine at two supermarkets, a pub and a book shop.
Sahnoun Daifallah, 42, of Bibury Road, from Gloucester, appeared before magistrates and pleaded not guilty to four charges of contaminating products.
He was arrested on Friday after a substance, believed to be urine, was sprayed over produce at Tesco in Quedgeley and Morrisons at Abbeydale. […]
In court prosecutor Liz Thomas said two days earlier Mr Daifallah used an improvised device to shower hundreds of children’s books at Waterstones in Cirencester.
He is also charged with releasing the liquid over food in the Air Balloon pub, near Cheltenham….