Tetanus

Tetanus

Definition:

It is an acute highly fatal infectious disease of all warm blooded animals and man. It is characterized by hyperesthesia, tetany, convulsions and death.

 

Etiology:

  • It is caused by toxins of Cl. Tetani. The organism is a Gram-positive rod forms spores, which can persist in soil for many years.
  • Tetani produces 3 toxic products:
  • Neurotoxin (tetanospasmin).
  • Hemolysin (tetanolysin).
  • Peripherally active non-spasmogenic toxin, which has a peripheral paralytic action.

 

Epizootiology

Susceptibility:

Horses, mules and donkeys are most susceptible. Sheep, goats, cattle, pigs, dogs and cats are also affected.

 

 

Sources of infection:  

Soil contaminated by feces of animals especially horses and contaminated surgical instruments are the main sources of infection.

 

Transmission:

  1. Deep puncture wounds of hooves are common in equines.
  2. Genital tract injuries at the time of parturition in cattle.
  3. Castration, sheering and docking in sheep.
  4. Teeth eruption, umbilical infection and dehorning.
  5. Injuries in mouth due to fibrous feed or in the gastrointestinal tract may cause what is called idiopathic tetanus.

 

Pathogenesis:

Tetanus spores remain localized in the wound until lowering of the local tissue oxygen tension occurs. The organisms proliferate and produce tetanolysin and tetanospasmin. The tetanolysin promotes local tissue necrosis. The tetanospasmin diffuses to the systemic circulation, bounds to motor end-plates and travel up peripheral nerve trunks and inhibits inhibitory neurotransmitters resulting in hypertonia and spasms. (it blocks the release of inhibitory neurotransmitters). The toxin causes spasmodic tonic contractions of the voluntary muscles by nerve irritation. Central potentiation of normal sensory stimuli occurs and innocuous stimuli cause exaggerated response s. death occurs by asphyxiation due to fixation of the muscles of respiration.

 

Clinical signs:

  • Increase in muscle stiffness accompanied by muscle tremors.
  • 3rd eyelid prolapse.
  • Tetanic spasm of the jaw muscles, erection of ears, dilatation of the nostrils and erection of the tail.
  • Mastication is prevented by tetany of the maseter muscles and saliva may drool from the mouth.
  • Constipation and urine retention.
  • Increased response to external stimuli (hyperesthesia).
  • In later stages, temperature may rise when muscular tone and activity are increased. Temperature may also increase due to drenching pneumonia or paralysis of heat regulating centers.
  • Recumbence, prostration and death.

 

Treatment:

  1. Elimination of the organism
    1. The wound should be cleaned and irrigated with hydrogen peroxide with local application of penicillin; this should be applied only after administration of the antitoxins.
    2. Parentral injection of penicillin in large doses.
  2. Neutralization of the toxins: Antitoxin should be administrated early. High doses are required 90.000 – 300.000 I.U. for 3 injections every 12 hours.
  3. Relaxation of muscle tetany using tranquilizers like chlorpromazine 1 mg/kg BWt. I.M. or 0.4 – 0.8 mg/kg BWt. I.V. twice daily.
    1. The use of stomach tube or I.V. feeding.
    2. Singing of the animal.
  • The use of enema and catheterization.
  1. Animal should be kept in quiet dark place with well beddedquarters.

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