tetanus

definition

· acute, often fatal disease

· caused by exotoxins produced in Clostridia tetani infections

· characterised by generalised muscle rigidity and convulsions

· preventable with immunisation

epidemiology

· was major problem during wars

· annual world mortality now is 1 000 000

· prevalent in rural areas with poor hygiene and medical services

· highest incidence in patients overage 60

· may reflect inadequate immunisation

· in Britain, 15 cases / year and in USA, 100 cases / year

aetiology and pathogenesis

Clostridium tetani

· organism

· anaerobic

· spore-bearing

· Gram-positive bacillus

· spores

· terminal (drumstick appearance)

· found in faeces, dust and soil

· esp. in hot damp climates

· esp. in soils rich with organic matter (esp. horse manure)

· resistant to antiseptics and heat (autoclaving for 10 min is satisfactory)

Infection

· Cl tetani is non-invasive

· infection only occurs when spores enter tissues and produce vegetative forms

· usual mode of entry through puncture wound or laceration

· injury may be trivial

· no history or evidence of wound in 20%

· germination of spores occurs in oxygen-poor media

· ie. necrotic tissue

· infection remains localised

· spores may enter tissue and lie dormant, reactivated by subsequent injury

Toxin

· produced by vegetative form

· released with lysis

Tetanospasmin

· exotoxin released when bacteria lysed in wound

· is potent neurotoxin (0.1 mg lethal)

· spreads to CNS through motor nerve or via blood stream and lymphatics

· principal effect is to block inhibitory pathways to spinal cord

· result is that stimuli to CNS are not damped down

· muscle rigidity with paroxysmal spasms or convulsions result

· effects are self-limiting

· no residual effects if recover

Tetanolysin

· another toxin

· is haemolysin

clinical presentation

Incubation period

· mean incubation period is 1 week

· varies (2-60 days) but usually < 15 days

· rapid onset = severe disease

Symptoms

· pain and stiffness in

· jaw

· abdomen

· back

· difficulty swallowing

Signs

· generalised rigidity

· difficulty opening mouth

· trismus or 'lockjaw'

· characteristic clenched teeth expression

· risus sardonicus

· spinal extension and neck retraction

· upper limb flexion and lower limb extension

· reflex spasms

· triggered by external stimuli (eg. noise, pressure)

· glottic and laryngeal spasms may cause cardio-respiratory arrest

· sympathetic dysfunction

· hypertension, tachycardia, sweating, arrhythmias, paralytic ileus

Complications

· muscle spasms disappear after 1-3 weeks

· most survivors recover completely after 6 weeks

· death usually occurs within 2 weeks

· respiratory complications are the major cause of death

· hypoxia, asphyxia or cardiorespiratory arrest

· aspiration

· pneumonia

investigations

· no specific laboratory tests

· Cl tetani cultured from wound in 1/3 of cases

Prophylaxis

Active immunisation with tetanus toxoid

Tetanus vaccine

· use tetanus toxin rendered non-toxic by action of formalin

· tetanus vaccines available

· TT (tetanus toxoid)

· triple antigen (diphtheria-tetanus-pertussis)

· CDT (child diphtheria-tetanus)

· ADT (adult diphtheria-tetanus)

· immunity conferred offers no immediate protection in unimmunised

· production of antibodies (antitoxins) by patient takes several weeks

· effects are long-lasting

Primary immunisation regimen (children)

· Triple Antigen at 2, 4 and 6 months

· CDT at 18 months and 5 years

Adult immunisation regimen

· only for those never immunised

· 3 courses of TT

· 6-12 week interval between 1st and 2nd

· 6-12 month interval between 2nd and 3rd

Booster

· ADT booster every 10 years

· if more than 20 years since booster, 2 boosters with 4-6 week interval

After injury

· if immunised, single booster injection will produce protective antibodies in one day

Types of wounds

· non-tetanus-prone wounds

· clean

· non-penetrating

· little tissue damage

· less than 6 hours old

· tetanus-prone wound

· open fracture

· puncture wound

· foreign body

· contamination

· extensive tissue damage

· more than 6 hours old

· septic wound

· animal bite

Tetanus toxoid boosters

· if patient not immune

· full TT course

· if wound not tetanus-prone and patient immune

· if < 10 years since booster, no TT

· if 10-20 years since booster, single TT

· if > 20 years since booster, two TT (separated by 4-6 weeks)

· if wound tetanus-prone and patient immune

· if < 2 years since booster, no TT

· if 2-20 years since booster, single TT

· if > 20 years since booster, two TT (separated by 4-6 weeks)

Passive immunisation with immunoglobulin

· TIG (tetanus immunoglobulin)

· solution of gamma-globulin fraction of donated plasma

· give in tetanus-prone wounds

· if not immune

· if immune and > 10 years since booster

· dose is 250 mg IM

· into different limb from TT

treatment

Wound care

· debridement of necrotic and contaminated tissue

Antibiotics

· tetanus spores destroyed by antibiotics

· vegetative form sensitive to antibiotics

· use penicillin G

· 2 million units q6h for 10 days

Antitoxin

· a more concentrated TIG for treating clinical tetanus

· neutralises circulating toxin

· does not affect toxins already fixed in CNS

Other

· control of spasms

· quiet dark room

· IV diazepam

· consider thiopental infusion

· care of airway

· ET tube and ventilation with severe spasms or respiratory failure

· tracheostomy

· hydration and nutrition

· autonomic dysfunction

prognosis

· depends on

· rapidity of onset

· severity of attack

· mortality rate is 60%