Botulinum toxin: From menace to medicine

The neurotoxins produced by the bacterium Clostridium botulinum that cause botulism are the most potent acute toxins known. There is no known cure for the flaccid muscular paralysis of botulism and for many people the disease evokes an emotive and fearful view of the toxins. Although rare, botulism is usually encountered as a food-borne disease that results from eating food contaminated with pre-formed toxin. Wound botulism and infant botulism are two other forms of the disease, although unlike food-borne botulism, these intoxications result from direct infection with the bacterium. The incidence of wound botulism has increased in recent years in drug users who inject heroin; infant botulism is now the most common form of the disease reported in the USA. Whilst these various forms of acquired botulism are frightening enough prospects, the toxins are now seen in the even more sinister context of use in weapons of biological warfare or bio-terrorism. The perception of these potent microbial toxins is changing. Whilst the pharmaceutical industry annually spends many millions of pounds searching for or designing synthetic chemicals that have specific pharmacological activities, with the botulinum neurotoxins, nature has done all the work for us. Over aeons of time a family of molecules have evolved having a unique combination of biological activities that can be used to clinical benefit.