Tetanus

1
Tetanus

• Philip L. Pokorski, Ph.D.
• University of MichiganDearborn
• Department of Biology

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Tetanus

• Caused by Clostridium Tetani
• Gram positive
• Spore-forming
• Anaerobic rod

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Reservoir

• Spores of C. tetani are found in soils throughout
  the world
• Spores are very resistant to harsh conditions
  
• heat
• radiation
• chemicals
• drying
• Spores can survive for a long time in
  environment---100yrs possibly!

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Tetanus (contd)

• Entry of C. tetani into the body usually involves
  implantation of spores into a wound
• After gaining entry, C. tetani spores can
  persist in the body for months, waiting for the
  proper low oxygen growth conditions to develop

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Tetanus (contd)

• When the oxygen levels of the surrounding tissue
  is sufficiently low, the implanted C. tetani
  spore then germinates into a new, active
  vegetative cell that grows and multiplies and
  most importantly produces tetanus toxin

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Tetanus (contd)

• The virulence factor (toxin) responsible for the
  symptoms of tetanus is called tetanospasmin
• Tetanospasmin is an extremely lethal neurotoxin
• Induces spastic paralysis
• by inhibiting release of inhibitory
  neurotransmitters
• Physiologic consequence is uncontrolled muscle
  contractions

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Tetanus (contd)

• As growing cells of C. tetani produce
  tetanospasmin at the wound site, the toxin starts
  to migrate along nerves into the Central Nervous
  System where it blocks the release of inhibitory
  neurotransmitters
• As a consequence of too much activator
  transmitters, muscles are OVERstimulated to
  repeatedly contractcalled spastic paralysis

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Tetanus (contd)

• A person suffering from tetanus undergoes
  convulsive muscle contractions of the jaw--called
  LOCKJAW
• The contractions by the muscles of the back and
  extremities may become so violent and strong
  that bone fractures may occur
• Unfortunately, the affected individual is
  conscious throughout the illness, but cannot stop
  these contractions

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Tetanus (contd)

• Death may occur from tetanus, often from cardiac
  (heart) and respiratory (lung) effects or
  secondary complications from the infection

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Diagnosis of Tetanus

• Tetanus is suspected upon exposure to a bite or
  puncture wound
• Because C. tetani exhibits such exquisite
  sensitivity to oxygen, it is very difficult to
  recover and/or grow from clinical specimens
• As a result, diagnosis is made on the basis of
  clinical findings and history

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Tetanus (contd)

• Tetanus is not common in U.S.A. because of
  mandatory vaccination
• However, a few cases/year in non- vaccinated
  or improper booster individuals
• Tetanus is still very common in Third World
  countriescausing several hundred thousand deaths
  per year
• Many of these deaths involve neonatal tetanus
  due to the umbilical cord being unsterilely cut

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Treatment of Tetanus

• Very difficult to treat once symptoms have
  developed
• Antitoxin is administered
• Muscle relaxants
• Supportive therapy (ventilator)
• Cleansing of the wound

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Treatment of Tetanus (contd)

• If recovery does occur, there are usually no
  long-term side effects.
• Recovered individuals do not necessarily
  develop natural Immunity against the
  infection--- because the very small amount of
  tetanus toxin produced during the infection
  does not elicit a strong, protective immune
  response which would produce enough antibodies
  against future re-infection

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Prevention of Tetanus

• A highly effective vaccine is available
• Tetanus immunity is achieved using a formalized
  tetanus toxoid
• Toxoid is administered as part of the
  childhood DPT vaccine
• 4 primary immunizations starting at 2
  months of age
• Boosters every 10 yrs
• they !_at_ hurt!!