domain responsible for mediating translocation of the light chain into the cell cytoplasm as the vacuole acidifies. the light chain is a m27-family zinc metalloprotease and is the active part of the toxin. it is translocated into the host cell cytoplasm where it cleaves the host protein snap-25, a member of the snare protein family, which is responsible for fusion. the cleaved snap-25 cannot mediate fusion of vesicles with the host cell membrane, thus preventing the release of the neurotransmitter acetylcholine from axon endings. this blockage is slowly reversed as the toxin loses activity and the snare proteins are slowly regenerated by the affected cell. the seven toxin serotypes (a–g) are traditionally separated by their antigenicity. they have different tertiary structures and sequence differences. while the different toxin types all target members of the snare family, different toxin types target different snare family members. the a, b, and e serotypes cause human botulism, with the activities of types a and b enduring longest in vivo (from several weeks to months). existing toxin types can recombine to create "hybrid" (mosaic, chimeric) types. examples include bont/cd, bont/dc, and bont/fa, with the first letter indicating the light chain type and the latter indicating the heavy chain type. bont/fa received considerable attention under the name "bont/h", as it was mistakenly thought it could not be neutralized by any existing antitoxin. botulinum toxins are closely related to tetanus toxin; the two are collectively known as clostridium neurotoxins and the light chain is classified by merops as family m27. nonclassical types include bont/x (p0dpk1), which is toxic in mice and possibly in humans; a bont/j (a0a242di27) found in cow enterococcus; and a bont/wo (a0a069cuu9) found in the rice-colonizing weissella oryzae. history initial descriptions and discovery of clostridium botulinum one of the earliest recorded outbreaks of foodborne botulism occurred in 1793 in the village of wildbad in what is now baden-württemberg, germany. thirteen people became sick and six died after eating pork stomach filled with blood sausage, a local delicacy. additional cases of fatal food poisoning in württemberg led the authorities to issue a public warning against consuming smoked blood sausages in 1802 and to collect case reports of "sausage poisoning". between 1817 and 1822, the german physician justinus kerner published the first complete description of the symptoms of botulism, based on extensive clinical observations and animal experiments. he concluded that the toxin develops in bad sausages under anaerobic conditions, is a biological substance, acts on the nervous system, and is lethal even in small amounts. kerner hypothesized that this "sausage toxin" could be used to treat a variety of diseases caused by an overactive nervous system, making him the first to suggest that it could be used therapeutically. in 1870, the german physician müller coined the term "botulism" to describe the disease caused by sausage poisoning, from the latin word botulus, meaning "sausage". in 1895 émile van ermengem, a belgian microbiologist, discovered what is now called clostridium botulinum and confirmed that a toxin produced by the bacteria causes botulism. on 14 december 1895, there was a large outbreak of botulism in the belgian village of ellezelles that occurred at a funeral where people ate pickled and smoked ham; three of them died. by examining the contaminated ham and performing autopsies on the people who died after eating it, van ermengem isolated an anaerobic microorganism that he called bacillus botulinus. he also performed experiments on animals with ham extracts, isolated bacterial cultures, and toxins extracts from the bacteria. from these he concluded that the bacteria themselves do not cause foodborne botulism, but rather produce a toxin that causes the disease after it is ingested. as a result of kerner's and van ermengem's research, it was thought that only contaminated meat or fish could cause botulism. this idea was refuted in 1904 when a botulism outbreak occurred in darmstadt, germany, because of canned white beans. in 1910, the german microbiologist j. leuchs published a paper showing that the outbreaks in ellezelles and darmstadt were caused by different strains of bacillus botulinus and that the toxins were serologically distinct. in 1917, bacillus botulinus was renamed clostridium botulinum, as it was decided that term bacillus should only refer to a group of aerobic microorganisms, while clostridium would be only used to describe a group of anaerobic microorganisms. in 1919, georgina burke used toxin-antitoxin reactions to identify two strains of clostridium botulinum, which she designated a and b. food canning over the next three decades, 1895–1925, as food canning was approaching a billion-dollar-a-year industry, botulism was becoming a public health hazard. karl friedrich meyer, a swiss-american veterinary scientist, created a center at the hooper foundation in san francisco, where he developed techniques for growing the organism and extracting the toxin, and conversely, for preventing organism growth and toxin production, and inactivating the toxin by heating. the california canning industry was thereby preserved. world war ii with the outbreak of world war ii, weaponization of botulinum toxin was investigated at fort detrick in maryland. carl lamanna and james duff developed the concentration and crystallization techniques that edward j. schantz used to create the first clinical product. when the army's chemical corps was disbanded, schantz moved to the food research institute in wisconsin, where he manufactured toxin for experimental use and provided it to the academic community. the mechanism of botulinum toxin action – blocking the release of the neurotransmitter acetylcholine from nerve endings – was elucidated in the mid-20th century, and remains an important research topic. nearly all toxin treatments are based on this effect in various body tissues. strabismus ophthalmologists specializing in eye muscle disorders (strabismus) had developed the method of emg-guided injection (using the electromyogram, the electrical signal from an activated muscle, to guide injection) of local anesthetics as a diagnostic technique for evaluating an individual muscle's contribution to an eye movement. because strabismus surgery frequently needed repeating, a search was undertaken for non-surgical, injection treatments using various anesthetics, alcohols, enzymes, enzyme blockers, and snake neurotoxins. finally, inspired by daniel b. drachman's work with chicks at johns hopkins, alan b. scott and colleagues injected botulinum toxin into monkey extraocular muscles. the result was remarkable; a few picograms induced paralysis that was confined to the target muscle, long in duration, and without side effects. after working out techniques for freeze-drying, buffering with albumin, and assuring sterility, potency, and safety, scott applied to the fda for investigational drug use, and began manufacturing botulinum type a neurotoxin in his san francisco lab. he injected the first strabismus patients in 1977, reported its clinical utility in 1980, and had soon trained hundreds of ophthalmologists in emg-guided injection of the drug he named oculinum ("eye aligner"). in 1986, oculinum inc, scott's micromanufacturer and distributor of botulinum toxin, was unable to obtain product liability insurance, and could no longer supply the drug. as supplies became exhausted, patients who had come to rely on periodic injections became desperate. for four months, as liability issues were resolved, american blepharospasm patients traveled to canadian eye centers for their injections. based on data from thousands of patients collected by 240 investigators, oculinum inc (which was soon acquired by allergan) received fda approval in 1989 to market oculinum for clinical use in the united states to treat adult strabismus and blepharospasm. allergan then began using the trademark botox. this original approval was granted under the 1983 us orphan drug act. cosmetics doctor performing botulinum toxin injection the effect of botulinum toxin type-a on reducing and eliminating forehead wrinkles was first described and published by richard clark, md, a plastic surgeon from sacramento, california. in 1987 clark was challenged with eliminating the disfigurement caused by only the right side of the forehead muscles functioning after the left side of the forehead was paralyzed during a facelift procedure. this patient had desired to look better from her facelift, but was experiencing bizarre unilateral right forehead eyebrow elevation while the left eyebrow drooped, and she constantly demonstrated deep expressive right forehead wrinkles while the left side was perfectly smooth due to the paralysis. clark was aware that botulinum toxin was safely being used to treat babies with strabismus and he requested and was granted fda approval to experiment with botulinum toxin to paralyze the moving and wrinkling normal functioning right forehead muscles to make both sides of the forehead appear the same. this study and case report of the cosmetic use of botulinum toxin to treat a cosmetic complication of a cosmetic surgery was the first report on the specific treatment of wrinkles and was published in the journal plastic and reconstructive surgery in 1989. editors of the journal of the american society of plastic surgeons have clearly stated "the first described use of the toxin in aesthetic circumstances was by clark and berris in 1989." jean and alastair carruthers observed that blepharospasm patients who received injections around the eyes and upper face also enjoyed diminished facial glabellar lines ("frown lines" between the eyebrows). alastair carruthers reported that others at the time also noticed these effects and discussed the cosmetic potential of botulinum toxin. unlike other investigators, the carruthers did more than just talk about the possibility of using botulinum toxin cosmetically. they conducted a clinical study on otherwise normal individuals whose only concern was their eyebrow furrow. they performed their study during 1987-1989 and presented their results at the 1990 annual meeting of the american society for dermatologic surgery. their findings were subsequently published in 1992. chronic pain william j. binder reported in 2000, that patients who had cosmetic injections around the face reported relief from chronic headache. this was initially thought to be an indirect effect of reduced muscle tension, but the toxin is now known to inhibit release of peripheral nociceptive neurotransmitters, suppressing the central pain processing systems responsible for migraine headache. society and culture economics as of 2018, botulinum toxin injections are the most common cosmetic operation, with 7.4 million procedures in the united states, according to the american society of plastic surgeons. qualifications for botox injectors vary by county, state, and country. botox cosmetic providers include dermatologists, plastic surgeons, aesthetic spa physicians, dentists, nurse practitioners, nurses, and physician assistants. the global market for botulinum toxin products, driven by their cosmetic applications, was forecast to reach $2.9 billion by 2018. the facial aesthetics market, of which they are a component, was forecast to reach $4.7 billion ($2 billion in the u.s.) in the same timeframe. us marketin 2020, 4,401,536 botulinum toxin type a procedures were administered. in 2019 the botulinum toxin market made us$3.19 billion. botox costbotox cost is generally determined by the number of units administered (avg. $10.00 - $30.00 per unit) or by the area ($200–1000) and depends on expertise of a physician, clinic location, number of units, and treatment complexity. insurancebotox for medical purposes is usually covered by insurance if deemed medically necessary by your doctor and covers a plethora of medical problems including overactive bladder (oab), urinary incontinence due to neurologic conditions, headaches and migraines, tmj, spasticity in adult patients, cervical dystonia in adult patients, severe axillary hyperhidrosis (or other areas of the body), blepharospasm, upper or lower limb spasticity. migrainesfor migraine induced headaches the fda-recommended dosage is 155 units and costs between $300 to $600 per treatment out of pocket when covered by insurance. hyperhidrosisbotox for excessive sweating is fda approved. cosmeticstandard areas for aesthetics botox injections include facial and other areas that can form fine lines and wrinkles due to every day muscle contractions and/or facial expressions such as smiling, frowning, squinting, and raising eyebrows. these areas include the glabellar region between the eyebrows, horizontal lines on the forehead, crow's feet around the eyes, and even circular bands that form around the neck secondary to platysmal hyperactivity. bioterrorism botulinum toxin has been recognized as a potential agent for use in bioterrorism. it can be absorbed through the eyes, mucous membranes, respiratory tract, and non-intact skin. the effects of botulinum toxin are different from those of nerve agents involved insofar in that botulism symptoms develop relatively slowly (over several days), while nerve agent effects are generally much more rapid. evidence suggests that nerve exposure (simulated by injection of atropine and pralidoxime) will increase mortality by enhancing botulinum toxin's mechanism of toxicity. with regard to detection, protocols using nbc detection equipment (such as m-8