Tetanus

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Tetanus

• Lock jaw

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Definition

• It is an acute highly fetal wound-infection
  toxemic disease of all animals and human which
  caused by the toxins of Clostridium tetani and
  characterized by an increased reflex excitability
  of the motor nerve centers with continuous
  spasmodic contraction of all striated muscles and
  clinically by hyperesthesia tetany, convulsion
  and death.

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Etiology

• C tetani, an anaerobe with terminal, spherical
  spores with typical drumstick appearance, is
  found in soil and intestinal tracts.
• It produces a number of toxins among them the
  most important are
• Neurotoxin or tetanospasmin It is a protein in
  nature and responsible for the characteristic
  signs of tetanus
• Hemolysin or tetanolysin It is a potent lethal
  toxin. It is responsible for the hemolysis around
  colonies on blood agar
• It is grows in blood agar producing colonies
• surrounded by complete zone of hemolysis
• after 24-48 hours.
• Spores can be killed by direct sunlight within 12
  days, boiling water within 10-15 minutes,
  30hydrogen peroxide within 10 minutes.

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Epidemiology

• Distribution tetanus occurs in all parts of the
  world in all farm animals. It is mainly appears
  as sporadic cases. In Egypt, it commonly occurs
  in all farm animals
• Animal susceptibility Human and solipeds
  (Horse, mules and donkeys) are the most
  susceptible followed by sheep, goats, pigs and
  cattle. Dogs and cats are rarely susceptible.
• Factors influencing susceptibility
• The disease may appear in all breeds, sexes and
  ages.
• The disease may appear any time of the year but
  outbreaks are common following castration,
  shearing, dehorning and other similar operations.

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Epidemiology

• Transmission
• Source of infection C. tetani organisms are
  commonly present in the feces of animals,
  especially horses, and in the soil contaminated
  by these feces.
• Mode of transmission The portal of entry is
  usually through deep puncture wounds but the
  spores may lie dormant in the tissues for some
  time and produce clinical illness only when
  tissue conditions favor their proliferation.
• The portal of entry may be different according to
  the animal species such as
• Horses Puncture wounds of the hooves are common
  sites.
• Cattle Introduction to the genital tract at the
  time of parturition is the usual portal of entry.
• Sheep following castration, shearing, docking,
  vaccinations, or injections of pharmaceuticals
  especially anthelmintics

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Epidemiology

• The portal of entry may be different according to
  the animal species such as
• Neonatal born animals tetanus occurs when there
  is infection in the umbilical cord associated
  with insanitary conditions at parturition.
• Pigs pigs may be infected through umbilicus or
  through castration wounds.
• Wounds of internal organs such as teeth eruptions
  and injuries of intestinal mucosa due to worm
  infestations may give rise to infection
  (idiopathic tetanus).
• Moreover, spores may stay dormant in tissues for
  several months of even years until the conditions
  become favorable for vegetation and proliferation
  of the organism and give rise to idiopathic
  tetanus (activated latent infection).

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Pathogenesis

• The spores of C tetani are unable to grow in
  normal tissue or even in wounds if the tissue
  remains at the oxidation-reduction potential of
  the circulating blood
• Suitable conditions for multiplication occur
• The bacteria remain localized in the necrotic
  tissue at the original site of infection and
  multiply. As bacterial cells undergo autolysis,
  the potent neurotoxin is released.
• The neurotoxin is absorbed by the motor nerves in
  the area and passes up the nerve tract to the
  spinal cord, where it causes ascending tetanus

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Pathogenesis

• The toxin causes spasmodic, tonic contractions of
  the voluntary muscles by interfering with the
  release of neurotransmitters from presynaptic
  nerve endings
• the excess is carried off by the lymph to the
  bloodstream and thus to the CNS, where it causes
  descending tetanus.
• Spasms affecting the larynx, diaphragm, and
  intercostal muscles lead to respiratory failure.
  Involvement of the autonomic nervous system
  results in cardiac arrhythmias, tachycardia, and
  hypertension.

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Clinical signs

• . The incubation period is about 7-10 days after
  injuries but it may be 3 weeks or more in some
  cases
• . Tetanus usually appears as sporadic or
  individual cases
• The mortality depends up on
• Nature of the wound deep badly soiled lacerated
  wound are accompanied with high mortality rate.
• The site of infection wound near the head or
  neck are more dangerous than those of the trunk
  or hind limbs.
• The incubation period (the infection doses) the
  shorter incubation period and higher mortality
  would be expected.
• The adopted treatment The course of the disease
  is different among and within the animal species.
  Generally, the duration of the fetal illness is
  usually 5-10 days in cattle and horse but sheep
  usually die in the third day.

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Clinical signs

• Initially, there is an increase in muscle
  stiffness, accompanied by muscle tremor.
• There is trismus with restriction of jaw
  movements, prolapse of the third eyelid, an erect
  cartridge of the ears, retraction of the eyelids
  and dilation of the nostrils, and hyperesthesia
  with exaggerated responses to normal stimuli
• stiffness of the hind limbs causing an unsteady,
  straddling gait, especially when backing or
  turning and the tail is held out stiffly,
  (hump-like)

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Clinical signs

• The animal may continue to eat and drink in the
  early stages but mastication is soon prevented by
  tetany of the masseter muscles, and saliva may
  drool from the mouth. If food or water is taken,
  attempts at swallowing are followed by
  regurgitation from the nose.
• Constipation is usual and the urine is retained,
  the rectal temperature and pulse rate are within
  the normal range in the early stages but may rise
  later when muscular tone and activity are further
  increased.
• As the disease progresses, muscular tetany
  increases and the animal adopts a 'sawhorse'
  posture.
• the hind limbs are stuck out stiffly behind and
  the forelegs forward. Sweating may be profuse and
  the temperature rises, often to 42C. The
  convulsions are at first only stimulated by sound
  or touch but soon occur spontaneously.
• finally, severe tetanic spasm during which
  respiration is arrested.

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Clinical signs

• Idiopathic tetanus, in which classical signs of
  tetanus occurs without wounds as in internal
  organs wounds as liver abscess or intestinal
  erosion from parasites
• Ascending tetanus, this type occurs in not highly
  susceptible animals as dog and cat where only
  nerve trunk near the toxigenic site absorb toxins
  to produce local muscular spasm
• Desending tetanus, this type occurs in highly
  susceptible animal as equine and humans where
  toxins disseminated via vascular channels to
  nerve endings in areas far away from toxigenic
  site and toxin reach to CNS produce generlized
  spasm begin from head to tail

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prognosis

• The prognosis is poor when the wound present near
  CNS, severe lacerated wound, high temperature,
  lock jaw, drenching pneumonia, idiopathic tetanus
  and signs rapidly progress.

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Diagnosis

• Field diagnosis Tetanus can be diagnosed from
  the clinical signs which can be supported by
  history of non-vaccination, history of wound and
  recent obstetrical or surgical interference.

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Diagnosis

• Laboratory diagnosis
• Samples air-dried impression smears from spleen,
  wound site, culture swab from wound site in
  anaerobic transport media spleen in sterile,
  leak proof container.

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Diagnosis

• Laboratory examination
• Direct microscopic examination of the lesions
  smear by Gram stain Demonstration of the
  characteristic drumstick spores is diagnostic.
  However, the results of this test are not
  satisfactory because the organism cannot be
  always demonstrated in the wound.

• Animal inoculation It is the most reliable
  technique for the laboratory diagnosis of
  tetanus. Two groups of mice can be used. One
  group can be protected by subcutaneous
  inoculation of 750 IU/mouse of tetanus antitoxin
  two hours before challenge. Both mice groups can
  be challenged by I/M inoculation in the hind leg
  with 0.25 ml of the supernatant of 48 hour cooked
  meat broth of the suspected sample. Rapid
  development of the clinical signs of tetanus in
  the non-protected group indicates the presence of
  tetanus toxins.

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Treatment

• The main principles in the treatment of tetanus
  are to
• Eliminate the causative bacteria
• Neutralize residual toxin
• Control muscle spasms until the toxin is
  eliminated or destroyed
• Maintain hydration and nutrition
• Provide supportive treatment

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Treatment

• Elimination of the causative agent
• Large doses of penicillin should be injected I/V
  as sodium benzyl penicillin 35,000 IU/kg followed
  after 12 hours by I/M inoculation of 2,000 IU/kg
  of procaine penicillin which should be repeated
  every 12 hours for 5-7 days.
• The wound (if found) should be treated by removal
  of necrotic tissue and irrigation with H2O2 or
  tincture of iodine then application of penicillin
  ointment. Treatment should be continued for 5
  days and wound should be left opened.

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• Neutralization of the unfixed toxin
• Administration of antitoxin for neutralization of
  unfixed neurotoxin in large doses during early
  stages has a great value in the treatment. Very
  large doses of antitetanic serum (100,000 IU)
  should be injected I/V, I/M, and S/C every 12
  hours, respectively. Local inoculation of
  antitetanic serum around the wound is indicated

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Treatment

• Relaxation of the muscle tetany
• Relaxation of muscle to control the convulsions
  and avoid asphyxia can be done by administration
  of tranquillizers such as Chlorpromazine (0.4-0.8
  mg/kg body weight intravenously, 1.0 mg/kg BW
  intramuscularly, three or four times daily)

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Treatment

• Additional supportive treatment
• Animal should be kept in dark quite well bedded
  place.
• If the animal is able to eat, soft laxative diet
  should be provided. In advanced cases, feeding
  through stomach tube or intravenous is necessary.
• In some cases, administration of enamas and
  catheterization may relieve the animal
  discomfort.

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Control

• Proper skin and surgical instrument disinfection
  for surgical procedures.
• Active immunization can be accomplished with
  tetanus toxoid
• it should be treated with 1,500-3,000 IU or more
  of tetanus antitoxin, which usually provides
  passive protection for up to 2 wk. Toxoid should
  be given simultaneously with the antitoxin and
  repeated in 30 days

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• Foals from non-vaccinated mares should receive
  their first vaccination for tetanus (tetanus
  toxoid) between 3 and 4 months of age. The second
  vaccination should be given between 4 and 5
  months of age, followed by a third vaccination
  between 5 and 6 months of age.
• Foals from vaccinated mares should receive their
  first vaccination for tetanus at 6 months of age,
  followed by booster vaccinations at 7 and 8 to 9
  months of age. Tetanus vaccination should be
  repeated annually thereafter.
• Brood mares should be vaccinated annually 4 to 6
  weeks before foaling to enhance the concentration
  of anti-tetanus antibodies in their colostrum.
• Adult non-vaccinated horses or horses with
  unknown status should receive an initial series
  of 2 doses of tetanus toxoid administered 3 to 6
  weeks apart, followed by an annual booster.
• Adult vaccinated horses (those that have
  previously been vaccinated with the 2-dose
  regimen), should receive an annual booster.

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For more information, details and questions

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