The invention provides epsilon toxin (ETX) produced by Clostridium perfringens type B or type D as a causative toxin for human multiple sclerosis (MS). The invention further identifies ETX binding receptor MAL for ETX mediated cell death and other toxin-logical activities in MS. Methods and compositions to prevent humans from multiple sclerosis (MS) and/or treating MS by directly or indirectly interfering with epsilon toxin (ETX), its binding receptor (e.g., MAL), or ETX-receptor interactions so as to inhibit or suppress downstream ETX mediated receptor signaling activities are provided. Also provided are various methods to detect, diagnose, monitor, assess multiple sclerosis (MS) by determining an expression level of ETX gene or its encoding protein in human patient suspected for and/or at risk for multiple sclerosis (MS).