Elevated expression of substance P is associated with gastrointestinal diseases such inflammatory bowel disease, Trichinella spiralis-induced enteritis and Clostridium difficile enterocolitis (Koch et al., 1987; Mazumdar and Das, 1992; Swain et al., 1992; Agro and Stanisz, 1993; Bernstein et al., 1993) and substance P levels correlate with symptom severity in cryptosporidiosis (Robinson et al., 2003). This evidence concerns the gene TAC1 and gastrointestinal disease.