 Experimental introduction of the serine protease into mice has been found to produce widespread pain associated with irritable bowel syndrome, as well as colitis, which is associated with all three diseases.Regional and temporal variations in those illnesses follow those associated with infection with the protozoan "Blastocystis".The "cold-chain" hypothesis is that psychrotrophic bacteria such as "Yersinia" and "Listeria" species contribute to the disease.