botulism botulism botulism is a rare and potentially fatal illness caused by a toxin produced by the bacterium clostridium botulinum. the disease begins with weakness, blurred vision, feeling tired, and trouble speaking. this may then be followed by weakness of the arms, chest muscles, and legs. vomiting, swelling of the abdomen, and diarrhea may also occur. the disease does not usually affect consciousness or cause a fever. botulisma 14-year-old with botulism, characterised by weakness of the eye muscles and the drooping eyelids shown in the left image, and dilated and non-moving pupils shown in the right image. this youth was fully conscious.pronunciation/ˈbɒtjʊlɪzəm/ specialtyinfectious disease, gastroenterologysymptomsweakness, trouble seeing, feeling tired, trouble speakingcomplicationsrespiratory failureusual onset12 to 72 hoursdurationvariablecausesclostridium botulinumdiagnostic methodfinding the bacteria or their toxindifferential diagnosismyasthenia gravis, guillain–barré syndrome, amyotrophic lateral sclerosis, lambert eaton syndromepreventionproper food preparation, no honey for children younger than onetreatmentantitoxin, antibiotics, mechanical ventilationprognosis~7.5% risk of death botulism can be spread in several ways. the bacterial spores which cause it are common in both soil and water. they produce the botulinum toxin when exposed to low oxygen levels and certain temperatures. foodborne botulism happens when food containing the toxin is eaten. infant botulism happens when the bacterium develops in the intestines and releases the toxin. this typically only occurs in children less than one year old, as protective mechanisms develop after that time. wound botulism is found most often among those who inject street drugs. in this situation, spores enter a wound, and in the absence of oxygen, release the toxin. it is not passed directly between people. the diagnosis is confirmed by finding the toxin or bacteria in the person in question. prevention is primarily by proper food preparation. the bacteria, though not the spores, are destroyed by heating it to more than 85 °c (185 °f) for longer than 5 minutes. honey can contain the organism, and for this reason, honey should not be fed to children under 12 months. treatment is with an antitoxin. in those who lose their ability to breathe on their own, mechanical ventilation may be necessary for months. antibiotics may be used for wound botulism. death occurs in 5 to 10% of people. botulism also affects many other animals. the word is from latin botulus, meaning sausage. signs and symptoms the muscle weakness of botulism characteristically starts in the muscles supplied by the cranial nerves—a group of twelve nerves that control eye movements, the facial muscles and the muscles controlling chewing and swallowing. double vision, drooping of both eyelids, loss of facial expression and swallowing problems may therefore occur. in addition to affecting the voluntary muscles, it can also cause disruptions in the autonomic nervous system. this is experienced as a dry mouth and throat (due to decreased production of saliva), postural hypotension (decreased blood pressure on standing, with resultant lightheadedness and risk of blackouts), and eventually constipation (due to decreased forward movement of intestinal contents). some of the toxins (b and e) also precipitate nausea, vomiting, and difficulty with talking. the weakness then spreads to the arms (starting in the shoulders and proceeding to the forearms) and legs (again from the thighs down to the feet). severe botulism leads to reduced movement of the muscles of respiration, and hence problems with gas exchange. this may be experienced as dyspnea (difficulty breathing), but when severe can lead to respiratory failure, due to the buildup of unexhaled carbon dioxide and its resultant depressant effect on the brain. this may lead to respiratory compromise and death if untreated. clinicians frequently think of the symptoms of botulism in terms of a classic triad: bulbar palsy and descending paralysis, lack of fever, and clear senses and mental status ("clear sensorium"). infant botulism an infant with botulismː despite not being asleep or sedated, he cannot open his eyes or move; he also has a weak cry. infant botulism (also referred to as floppy baby syndrome) was first recognized in 1976, and is the most common form of botulism in the united states. infants are susceptible to infant botulism in the first year of life, with more than 90% of cases occurring in infants younger than six months. infant botulism results from the ingestion of the c. botulinum spores, and subsequent colonization of the small intestine. the infant gut may be colonized when the composition of the intestinal microflora (normal flora) is insufficient to competitively inhibit the growth of c. botulinum and levels of bile acids (which normally inhibit clostridial growth) are lower than later in life. the growth of the spores releases botulinum toxin, which is then absorbed into the bloodstream and taken throughout the body, causing paralysis by blocking the release of acetylcholine at the neuromuscular junction. typical symptoms of infant botulism include constipation, lethargy, weakness, difficulty feeding, and an altered cry, often progressing to a complete descending flaccid paralysis. although constipation is usually the first symptom of infant botulism, it is commonly overlooked. honey is a known dietary reservoir of c. botulinum spores and has been linked to infant botulism. for this reason, honey is not recommended for infants less than one year of age. most cases of infant botulism, however, are thought to be caused by acquiring the spores from the natural environment. clostridium botulinum is a ubiquitous soil-dwelling bacterium. many infant botulism patients have been demonstrated to live near a construction site or an area of soil disturbance. infant botulism has been reported in 49 of 50 us states (all save for rhode island), and cases have been recognized in 26 countries on five continents. complications infant botulism has no long-term side effects. botulism can result in death due to respiratory failure. however, in the past 50 years, the proportion of patients with botulism who die has fallen from about 50% to 7% due to improved supportive care. a patient with severe botulism may require mechanical ventilation (breathing support through a ventilator) as well as intensive medical and nursing care, sometimes for several months. the person may require rehabilitation therapy after leaving the hospital. cause a photomicrograph of clostridium botulinum bacteria. clostridium botulinum is an anaerobic, gram-positive, spore-forming rod. botulinum toxin is one of the most powerful known toxins: about one microgram is lethal to humans when inhaled. it acts by blocking nerve function (neuromuscular blockade) through inhibition of the excitatory neurotransmitter acetylcholine's release from the presynaptic membrane of neuromuscular junctions in the somatic nervous system. this causes paralysis. advanced botulism can cause respiratory failure by paralysing the muscles of the chest; this can progress to respiratory arrest. furthermore, acetylcholine release from the presynaptic membranes of muscarinic nerve synapses is blocked. this can lead to a variety of autonomic signs and symptoms described above. in all cases, illness is caused by the botulinum toxin produced by the bacterium c. botulinum in anaerobic conditions and not by the bacterium itself. the pattern of damage occurs because the toxin affects nerves that fire (depolarize) at a higher frequency first. mechanisms of entry into the human body for botulinum toxin are described below. colonization of the gut the most common form in western countries is infant botulism. this occurs in infants who are colonized with the bacterium in the small intestine during the early stages of their lives. the bacterium then produces the toxin, which is absorbed into the bloodstream. the consumption of honey during the first year of life has been identified as a risk factor for infant botulism; it is a factor in a fifth of all cases. the adult form of infant botulism is termed adult intestinal toxemia, and is exceedingly rare. food toxin that is produced by the bacterium in containers of food that have been improperly preserved is the most common cause of food-borne botulism. fish that has been pickled without the salinity or acidity of brine that contains acetic acid and high sodium levels, as well as smoked fish stored at too high a temperature, presents a risk, as does improperly canned food. food-borne botulism results from contaminated food in which c. botulinum spores have been allowed to germinate in low-oxygen conditions. this typically occurs in improperly prepared home-canned food substances and fermented dishes without adequate salt or acidity. given that multiple people often consume food from the same source, it is common for more than a single person to be affected simultaneously. symptoms usually appear 12–36 hours after eating, but can also appear within 6 hours to 10 days. no withdrawal periods have been established for cows affected by botulism. lactating cows injected with various doses of botulinum toxin c have not resulted in detectable botulinum neurotoxin in milk produced. using mouse biossays and immunostick elisa tests, botulinum toxin was detected in whole blood and serum but not in milk samples, suggesting that botulinum type c toxin does not enter milk in detectable concentrations. cooking and pasteurization denatures botulinum toxin but does not necessarily eliminate spores. botulinum spores or toxins can find their way into the dairy production chain from the environment. despite the low risk of milk and meat contamination, the protocol for fatal bovine botulism cases appears to be incineration of carcasses and withholding any potentially contaminated milk from human consumption. it is also advised that raw milk from affected cows should not be consumed by humans or fed to calves. wound wound botulism results from the contamination of a wound with the bacteria, which then secrete the toxin into the bloodstream. this has become more common in intravenous drug users since the 1990s, especially people using black tar heroin and those injecting heroin into the skin rather than the veins. wound botulism accounts for 29% of cases. inhalation isolated cases of botulism have been described after inhalation by laboratory workers. injection symptoms of botulism may occur away from the injection site of botulinum toxin. this may include loss of strength, blurred vision, change of voice, or trouble breathing which can result in death. onset can be hours to weeks after an injection. this generally only occurs with inappropriate strengths of botulinum toxin for cosmetic use or due to the larger doses used to treat movement disorders. following a 2008 review the fda added these concerns as a boxed warning. mechanism the toxin is the protein botulinum toxin produced under anaerobic conditions (where there is no oxygen) by the bacterium clostridium botulinum. clostridium botulinum is a large anaerobic gram-positive bacillus that forms subterminal endospores. there are eight serological varieties of the bacterium denoted by the letters a to h. the toxin from all of these acts in the same way and produces similar symptoms: the motor nerve endings are prevented from releasing acetylcholine, causing flaccid paralysis and symptoms of blurred vision, ptosis, nausea, vomiting, diarrhea or constipation, cramps, and respiratory difficulty. botulinum toxin is broken into eight neurotoxins (labeled as types a, b, c , d, e, f, and g), which are antigenically and serologically distinct but structurally similar. human botulism is caused mainly by types a, b, e, and (rarely) f. types c and d cause toxicity only in other animals. in october 2013, scientists released news of the discovery of type h, the first new botulism neurotoxin found in forty years. however, further studies showed type h to be a chimeric toxin composed of parts of types f and a (fa). some types produce a characteristic putrefactive smell and digest meat (types a and some of b and f); these are said to be proteolytic; type e and some types of b, c, d and f are nonproteolytic and can go undetected because there is no strong odor associated with them. when the bacteria are under stress, they develop spores, which are inert. their natural habitats are in the soil, in the silt that comprises the bottom sediment of streams, lakes, and coastal waters and ocean, while some types are natural inhabitants of the intestinal tracts of mammals (e.g., horses, cattle, humans), and are present in their excreta. the spores can survive in their inert form for many years. toxin is produced by the bacteria when environmental conditions are favourable for the spores to replicate and grow, but the gene that encodes for the toxin protein is actually carried by a virus or phage that infects the bacteria. little is known about the natural factors that control phage infection and replication within the