Botulism

- a disease caused by action of a heat-labile protein neurotoxin elaborated by Clostridium

botulinum
- botulism is a rare but potentially life-threatening neuroparalytic syndrome

History
- this disease has a lengthy history. The first investigation of botulism occurred in the
1820s with a case report on hundreds of patients with “sausage poisoning” in a Southern
German town
- several decades later in Belgium, the association was demonstrated between a
neuromuscular paralysis and ham infected by a spore-forming bacillus which was
isolated from ham. The organism was named Bacillus botulinus after the Latin word for
‘sausage’ - ‘botulus’
- botulism has become a subject of speculation as a possible bioterrorism threat
- botulism is usually due to ingestion of preformed toxin produced by organisms growing
in improperly preserved food but it can also be caused by infection of wound with
Clostridium botulinum with toxin production in vivo. The disease, although rare, has a
worldwide distribution

The modern syndrome of botulism occurs in 4 forms, differentiated by mode of acquisition:

Types of Botulism
1. food-borne botulism(USA 25%, Russia 95-99%)
- ingestion of food contaminated by preformed botulinum toxin
2. wound botulism(USA 3%)
- infection of a wound by C. botulinum with subsequent in vivo production of neurotoxin
3. infant botulism(USA 72%)
- ingestion of clostridial spores which then colonize host’s GIT and release toxin
produced in vivo
4. adult enteric infectious botulism
- adult infectious botulism of unknown source; infant-like botulism
- adult infectious botulism is only occasionally reported
- similar to infant botulism in a way that toxin is produced in vivo in GIT of an infected
adult host

Etiology
C. botulinum:
- anaerobic, gram negative bacilli
- rod-shaped, spore-forming bacteria
- does not form capsule
- types of C. botulinum have been recognized on the basis of antigenic differences in the
toxins which are produced. A single strain almost always produces only one toxin type
- C. botulinum toxin types: A, B, ( ), ( ), D, E, F, G
- types A, B, E, and rarely F, cause disease in human
- types C and D are associated with botulism in birds(ducks, chickens) and non-human
mammals(cattle)
- type G have been isolated from soil but does not cause disease
- ubiquitous
- widely distributed in terrestrial and marine environments and thus commonly
contaminate vegetables, fruits, marine products
- easily isolated from surfaces of seafood and in soil
- environmental parameters:
1. restricted oxygen exposure(either an anaerobe/semi-anaerobe environment)
2. low acidity(pH>4.6) of water
3. temperature of 25-37°C for ideal growth
- type E may grow in temperatures as low as 4°C
- some strains(A and B) produce proteolytic enzymes that denature and “spoil” the foods
that they inhabit, leaving them with an unpleasant appearance, taste or smell
- other strains don’t overtly change the food and contamination cannot reliably be
suspected on the basis of look, odor, taste of food
- C. baratii and C. butyricum produce type E and F botulinum-like neurotoxins

Characteristics of Groups of C. botulinum and Toxins That Produce Human Disease

Group Toxins Produced Proteolysis Heat Resistance of Spores Disease Severity
I A, B, F Yes High Severe
II B, E, F No Low Less Severe

Botulinum Toxin
- is the most poisonous substance known to man
- is the most potent bacterial toxin
- 1g of aerosolized botulinal toxin could kill at least 1.5 million people
- botulinal toxin is 375500 times more active than some poison of rattlesnake
- the toxin is not released from spores
- the toxin itself has no smell/taste
- botulinal toxin is synthesized as a heat-labile polypeptide
- is composed of neurotoxin, hemagglutinin and non-toxic component(protein with
unknown, perhaps protective, function)
- heavy chain and light chain joined by disulfide bond
- combined molecular weight of 150-165kDa; heavy chain of about 100kDa
- can be denatured by heating above 80°C
- resistant to degradation by gastric acidity and human alimentary enzymes
- activation by trypsin enhances toxicity of type E and non-proteolytic types B and F toxins
- resistant to action of high concentration of table salt(18%)
- unstable to action of alkaline solution(pH>8.0)
- is inactivated in chlorinated water after 20 minutes of exposure in fresh water after 3-6
days
 Minimum Lethal Dose(µg/kg)
Botulinal toxin 0.0003
Curare 500
Sodium cyanide 10000

Mechanism of Action of Botulinal Toxin

1. after ingestion, botulinal toxins are absorbed from the intestinal tract and transported
via lymph and blood to individual motor nerve synapses. Botulinal toxin is primarily
absorbed by stomach and small intestine although large intestine is capable of absorbing
toxins as well. Regardless of route of entry into the body, the toxin disperses widely via
vascular system to bind the presynaptic sides of peripheral cholinergic synapses at
ganglia and neuromuscular junctions
2. the cranial nerve terminals are involved earlier and more severely
3. all botulinal toxins(types A, B, E) inhibit release of acetylcholine at peripheral cholinergic
synapses, including those of all autonomic preganglionic and parasympathetic
postganglionic fibers and those at neuromuscular junction
4. heavy chain of toxin binds rapidly to receptors on the presynaptic terminal surface(of
membrane presynaptic and motor neuron). Then some/all of the toxin molecules
translocate through membrane. Light chain translocate into nerve via cell-mediated
endocytosis
5. there is a slow paralytic step that may partially depend upon temperature of neuron. The
process is irreversible and synapse is permanently damaged
6. recovery of function depends on budding and growth of new presynaptic endplates.
Return of synaptic function requires sprouting of new presynaptic terminal with
subsequent formation of a new synapse, a process that requires approximately 6 months
7. adrenergic synapses are not affected by the toxin, nor does the toxin appear to permeate
blood-brain barrier, therefore limiting involvement to peripheral cholinergic nervous
system
8. type B toxin has been detected in serum and feces later in the course of illness than has
either type A or E. Type B toxin may persist in the serum for as long as 30 days after
exposure, raising possibility of production of the toxin in vivo
9. gross and histologic findings on post-mortem examination are inconsistent and non-
diagnostic. There are no specific pathologic findings on gross/histologic examination in
any other forms of botulism
10. patients with botulism don’t develop Ab to botulinum toxin, recurrent illness has been
reported
Epidemiology
USA(44 states) 708 food-borne outbreaks involving
1814 persons
between 1899-1974
California, Washington, over ½ of total cases
Colorado, Oregon, New
Mexico
USA 474 outbreaks involving nearly 1050
(large population from persons between 1950-1990
Alaska)
France about 300 food-borne outbreaks between 1979-1988
UK 9 outbreaks between 1922-1988
27 persons 1989
Russia 4374 persons between 1993-2003

Sources of Infection and Reservoir

- environment(soil of lakes, seas and oceans)
- animals(mammals, birds, fish, mollusks). Outbreaks of botulism occurs in animals such
as fowl, cattle, minks as well as in human
- sick person(patients with botulism) don’t represent epidemiological danger. There is no
people-people transmission
- illness may affect all ages from newborns to adults. Children acquire disease less often
than adults, perhaps reflecting protection/more fastidious eating habits
- outbreaks are most frequently in summer/autumn

1. Food-borne botulism(alimentary route)

- toxin types A, B and E have all been associated with food-borne botulism
- food-borne cases of botulism are most commonly recognized as small outbreaks,
usually involving home canned foods such as fruits, vegetables, fish
- type E outbreaks is caused exclusively by fish/fish products
- food that are home-preserved are more frequently incriminated, accounting for about
90% of outbreaks. Commercial products and restaurants are occasional sources
- outbreaks occur with geographical distribution that parallels distribution of spores in
soil. In contrast to predominance of type A outbreaks in the USA, outbreaks in Europe
are mostly type B, and those in Japan mostly type E

C. botulinum Country Food

Type A USA(apart from Alaska), home-preserved vegetables
Spain, Italy, China
USA home-canned asparagus,
beans, peppers
China home-fermented bean curd
Type B(non-proteolytic) Central Europe home-canned meat
Type E Alaska, Japan, Canada, fermented foods/preserved
Scandinavia fish products
Food-borne botulism in Russia
- home preserved mushrooms(60-80%)
- preserved vegetables, fruits
- salt and smoked fish, caviar(15-20%)
- meat products(sausage, ham, gammon)(5%)

Food Cases(%)
Vegetables 57
Fruits and fish products 15
Preserved fruits 12
Condiments 8
Assorted products(beef, pork, poultry, milk products, soup) 9

2. Wound botulism
- contact mechanism
- primarily in young persons, especially males
- during summer
- puncture wounds, subcutaneous abscesses, deep space infections, abrasions,
lacerations, open fractures, surgical incisions, and even closed hematoma without
appreciable skin defects
- groups of risk:
1. persons working in agriculture and animal industries(farmers, gardeners,
farm-hands)
2. injection drug users(particularly among those using “black-tar” heroin by
subcutaneous/IM route)
- how heroin becomes contaminated with clostridial organisms/their toxin is unknown.
Cases have been reported in IV drug users and complicating sinusitis in chronic cocaine
sniffers

3. Infant botulism
- since 1976, over 900 cases of infant botulism in USA
- USA(Utah, Pennsylvania and California), England, Australia
- production of toxin in intestine after germination and colonization by spores of
C. botulinum type A, B or C, C.baratii type F, or C.butyricum type E
- ingestion of raw honey
- affects children aged <1 year old; most cases involve infants 6 months old or younger
(3-24 weeks old); males more often than females
- more cases among breast-fed than bottle-fed children
- infant botulism may account for some cases of sudden infant death syndrome(SIDS)
Pathogenesis(I)

Pathogenesis(II)
Pathogenesis(III)

Clinical Manifestations
- incubation period: from 2-6 hours up to 8-10 days; usually 12-48 hours
- prodromal symptoms:
1. gastroenteric variant: nausea, vomiting(1-3 times/day), abdominal pain, diarrhea
(1-2 times/day) followed by constipations, dry mouth
(sometimes with sore throat)
2. ocular variant: blurred vision(muscae volitantes, “in a fog”, dim-out), acute
farsightedness
3. acute respiratory failure: sensation of air shortage, sense of discomfort/pain in
thorax, superficial but not rapid breathing

General Intoxication Symptoms

- headache
- dizziness
- muscular weakness
- insomnia
Paralytic Period
- period of the best development of symptoms
- acute symmetrical impairment of cranial nerve function
- bilateral symmetrical descending muscle paralysis of upper and lower extremities and
trunk

1. amplification of complains
and prodromal symptoms;
descending muscle weakness
2. eyesight(III, IV, VI nerves) - ophthalmoplegia
III n. occulomotorius - diplopia
IV n. trochlearis - mydriasis, pupillary dilation
VI n. abducens - anisocoria
- loss of pupillary reflex
- ill-sustain accommodation, paralysis of
accommodation
- convergent strabismus(VI n.)
- divergent strabismus(III n.)
- ptosis
- nystagmus
- immobility of eyeballs
3. swallowing and articulation - bulbar palsy
(IX, X, XII nerves) - pharyngeal, laryngeal palsy
IX n. glossopharyngeus - dysphagia
X n. vagus - loss of pharyngeal reflex, pharyngoplegia
XII n. hypoglossus - falling palate(palatoplegia)
- flow of fluid into nasal cavity in swallowing
- hoarse voice and nasal twang(hypernasal voice,
snuffing voice), aphonia
- dysarthria(XII n.), slurring speech
- paralysis of vocal chords
4. respiratory disturbances - absence of diaphragmatic breath
- diaphragmatic paralysis
- immovability of intercostal muscles
- loss of tussal reflex
- dyspnea, tachypnea, apnea
- acute respiratory failure
5. facial palsy - facial weakness, palsy facial muscles, loss of facial
movement, mask-like face, amimia
- smoothed-down nasolabial fold
- impossibility to grin/to frown and to frown eyebrows
6. CVS - expansion of heart borders
- dullness of cardiac sounds
- normal/slow heart rate, pulse is normal
- normal blood pressure/hypotonia
- tachycardia, extrasystole, arrhythmia(in severe cases
toxic myocarditis)
7. digestive tract - dryness of mucous membranes of mouth and tongue
- viscous saliva
- paralysis of intestinal muscles(flatulent distention)
- meteorism
- constipation(common after neurologic signs appear)
 8. general view of patient - languid, adynamic
- shaky, “drunk” gait(“swing”, “sways”)
- cogwheel symptom
- patient can’t hold head in vertical position and can’t
hold tableware
- weakness of arms and legs
- no pyramidal tract signs; deep tendon reflexes are
usually normal(but may be depressed/absent)
9. sensory NS - not affected
10. consciousness - is kept
11. body temperature - normal/low-grade fever
- fever may develop later in severe cases if secondary
microbial complications occur

Cardinal Clinical Features of Botulism

- symmetrical neurologic deficits
- neurological manifestations are symmetrical and descending
- patient remains responsive
- mental processes are generally clear(i.e. most patients are lucid and responsive,
although occasionally patients are anxious, agitated, or unusually drowsy)
- no sensory deficits with exception of blurred vision
- there are no sensory disturbances: no numbness, decreased perception to touch, or
paresthesias(vision may be impaired because of involvement of extraocular muscles)
- absence of fever
- fever is absent easly in the disease, but may develop later if infectious complications
occur)
- normal/slow heart rate and normal temperature

Complications
- pneumonia
- aspiration
- atelectasis
- tracheobronchitis
- urinary tract infection
- cardiac arrhythmias
- serum sickness
- anaphylaxis
- secondary microbial complication

Types of Botulism and Their Clinical Features

1. food-borne botulism
- all ages affected
- symmetrical descending paralysis that may progress rapidly
- common symptoms are diplopia, blurred vision, dysphagia, dysphonia, respiratory
distress
2. wound botulism
- presence of infected wound in 2 weeks before onset of symptoms
- incubation period has ranged from 4-14 days(with median of 6 days)
- no suspected food exposure
- absence of prodromal GI symptoms common to food-borne botulism
- same symptoms as food-borne form but fever is often present(but this probably results
from concurrent bacterial infection of wound by non-clostridial species)
3. infant botulism
- constipation, weak suck, anorexia, poor feeding(feeding difficulties as a result of poor
ability to suck and pooled oral secretions), weak cry, hypotonia, loss of head control
(loss of facial movement, inability to hold head up), drooling, irritability, lethargy
followed by progressive general weakness, impaired respiration and occasionally death
- symptoms usually progress for 1-3 weeks before peaking
- recovery takes several months and may involve episodic relapse and remissions
4. adult enteric infectious botulism
- affects patients >12 months old
- clinically compatible with botulism, without history of ingestion of suspected food and
without wounds

Diagnosis
1. history and physical examination
2. routine lab test
- blood cell count, sedimentation rates, urinanalysis, serum electrolytes, CSF, blood
enzymes are normal unless there are secondary complications
3. bioassay in mice for detection and identification of botulinum toxin
- mouse neutralization test is used and takes 24-48 hours
- demonstrate botulinum toxin in serum(blood), stool(feces), vomitus, gastric contents,
and suspected food items via injecting mice and protecting via antitoxin
4. bacteriological assay
- specimens of feces and food should be cultured for C. botulinum
5. immunosorbent assay
- toxin may be detected by an enzyme-linked immunosorbent assay in the patient’s feces
particularly in infant botulism and other causes resulting from intestinal colonization
6. electromyography(EMG)
- electrophysiologic studies show normal nerve conduction velocities but EMG often
abnormal with facilitation(an incremental increase) of M-wave amplitude when high
frequency(20-50/sec) repetitive stimuli are applied
7. ECG(toxic myocarditis)

Food-borne botulism diagnosis:

- serum analysis for botulinum toxin by bioassay in mice
- analysis of stool, vomitus, food may also reveal toxin
- EMG studies may be useful but are not generally required

Wound botulism diagnosis:

- history and physical examination
- history should include question about injection drug use and trauma
- fever and leukocytosis(about 50%)
- isolation of C. botulinum from wound site
- serum assays for toxin are frequently negative and therefore rarely helpful
- stool and vomitus assay for toxin yield nothing and should not be attempted
- EMG is useful diagnostic tool
Infant botulism diagnosis:
- a presumptive diagnosis should be made based upon clinical presentation and
electrophysiologic findings on EMG
- serum samples for toxin are often negative
- definitive diagnosis required recovery of C. botulinum toxin from stool samples
- EMG not pathogenic and may be normal in early course

Adult enteric infectious botulism diagnosis:

- changes same as infant botulism in terms of clinical findings and test results

Differential Diagnosis
- food-borne poisoning
- mushroom poisoning
- fish poisoning
- myasthenia gravis
- Lambert-Eaton myasthenia syndrome(LEMS)
- Tick paralysis
- Guillain-Barre syndrome
- infectious diseases(poliomyelitis, meningitis, encephalitis)
- cerebrovascular accident involving basilar artery
- stroke
- chemical intoxications(eg: methyl alcohol, organophosphorus compounds, atropine)
- carbon monoxide poisoning
- heavy metal intoxication
- trichinosis
- diphtheria

Wound botulism differential diagnosis:

- tetanus
- rabies
- myonecrosis

Infant botulism differential diagnosis:

- includes all of the above except LEMS, stroke, as well as brain stem encephalitis, drug
ingestion, metabolic encephalopathy, sepsis

Therapy
- any patient with clinical signs, symptoms/history suspicious for botulism should be
hospitalized immediately under clinical indications and monitored for signs of
respiratory failure
- hospitalize and begin treatment without waiting for definitive diagnosis
- antitoxin is effective only if toxins have not yet bond to tissues, so do not delay

1. obligatory hospitalization of all under clinical indications

patients with diagnosis of botulism
2. induction of vomiting and gastric
lavage antiseptic solution(K ), sodium
- with purpose to facilitate hydrocarbonate 5%
elimination of unabsorbed toxin
3. specific serotherapy - skin testing before administration of
- trivalent(A, B, E) equine-origin antitoxin. Guidelines for skin testing,
antitoxin(equine serum trivalent desensitization and dosing including
botulism antitoxin(A, B, E)) antitoxin package
- with purpose to neutralize - type A = 10000IU
circulatory toxin type B = 5000IU
type E = 10000IU
- course 3-4 days
- IV/IM, 1 time during course
- repeated administration without skin
testing, only monovalent(univalent)
antitoxin
4. human botulinum Ig - without preliminary skin tests
- type A = 450-500IU
type B = 300-600 IU
type E = 250-500 IU
- IV, 1 time during course
5. specific antitoxin antibotulinic - 250-300ml 2-3 times/day
fresh frozen plasma - IV
6. non-specific detoxification therapy - colloid and crystalloid solution, solution of
NaCl 0.9%, solution of glucose 5%,
enterosorbents
7. intubation with mechanical - indications: respiratory failure, inadequate/
ventilation worsening upper airway competency, vital
capacity <30%
8. monitoring of cardiac and - pulse oximetry
respiratory functions - spirometry
- arterial blood gas measurement
- clinical evaluation of ventilation, perfusion
and upper airway integrity
9. hyperbaric oxygenation - under individual parameters:
- mild course: 1-2 times
- moderate course: 3-5 times
- severe course: 4-10 times
10. antimicrobial therapy - course of antimicrobial treatment: 7-10 days
- has been recommended because - antibiotics:
of possibility that toxin may - chloramphenicol(Levomycetin) 0.5g
continue to be produced in GIT 4 times/day
after germination of spores of - tetracycline 0.3g/day
C. botulinum ingested with - ampicillin 0.5g/day
contaminated food - penicillin G 3 million units IV 6 times/day
- infectious complications may - metronidazole 500mg 3 times
require antimicrobial therapy - cephalosporin(3rd generation)
- aminoglycosides contraindicated because it
will increase intensity of synapse blockage
and worsen condition
11. other treatment - symptomatic therapy
- purgation: laxative/enema/other cathartics
- enteral, parenteral nutrition, nasal and
nasogastric feeding
- care of patients to prevent pneumonia, bed
sores, item traumas and muscle atrophy
- physical medicine and physical medical
culture(recovery phase)
Guidelines For Skin Testing and Desensitization
- trivalent(A, B, E) equine-origin antitoxin is administered fractionally according to
Bezredka
- 0.1ml diluted(1:100) trivalent(A, B, E) equine-origin antitoxin introduced
intracutaneously. If allergic reaction absent, 20 minutes later all medical dose introduced
- 0.1ml non-diluted trivalent(A, B, E) equine-origin antitoxin introduced subcutaneously. If
allergic reaction absent, 30 minutes later all medical dose introduced

Prevention
- biggest problem is widespread occurrence of spores in environment
- with the preventive purpose:
- give antitoxin to all others that ate contaminated food even if symptoms have not
developed
- antitoxin(A, B, E) 2000IU IM, each type; a trivalent antitoxin is available for prophylaxis
after exposure and also for those presenting with early symptoms. It neutralizes toxins
of C. botulinum types A, B, and E. Contraindications: history of hay fever, asthma/other
allergies
- heating food 80-100°C for 10 minutes inactivates toxin
- home canners must use proper sterilization technique(proper methods)
- public health measures are aimed at prevention during food preparation for
preservation, especially when done at home
- newborns under 1 year old should avoid honey[USA only]

Prognosis
- mortality higher in type A than type B
- severity depends on quantity of food ingested(contaminated)
- reversal of illness does not occur immediately following administration of antitoxin. In
fact the disease may continue to progress
- requires hospitalization for 1-3 months
- recovery from botulism does not confer immunity because the amount of toxin necessary
to immunize far exceeds the quantity which will cause disease or even death. Active
immunization with botulinum toxoid is not needed because the disease is rare