Porcine stress syndrome

Porcine stress syndrome is a genetic condition that causes sudden death and pale, soft, exudative muscle (PSE) resulting in dark, dry, tough meat.

Alternative names: PSS, malignant hyperthermia, PSE, halothane gene

Information

This term covers a group of conditions associated with a recessive gene. It includes acute stress and sudden death (malignant hyperthermia); pale, soft, exudative muscle; dark, dry and hard meat; and necrosis of the dorsal muscle. Heavy-muscled pigs are more likely to have the gene. The pig is either homozygous recessive (susceptible) heterozygous, or free of the gene. The gene can be identified by a pig's response to halothane gas (an anesthetic), but recently, researchers have developed a genetic test that identifies homozygous and heterozygous carriers with only one drop of blood or one hair. Dorsal muscle necrosis is a more localized form of the porcine stress syndrome.

When the pig is homozygous, after a period of muscle activity, there is a change in muscle metabolism from aerobic to anaerobic and biochemical abnormalities develop. Body tissues become acidic and the temperature increases considerably, up to 42ºC.

Symptoms

All ages

  • Very active muscle tremors.
  • Twitching of the face.
  • Rapid breathing.
  • The skin is often red and presents some kind of rash.
  • Death often occurs within 15-20 minutes.
  • Something distinctive is the onset of rigor mortis (muscle stiffness after death) in about 5 minutes after death.
  • Increased temperature (> 41ºC).

 

Causes / Contributing Factors

  • The disease is triggered by a sudden muscle activity.
  • The carrier pig is genetically susceptible.

Diagnosis

Diagnosis is based on a sudden onset, clinical signs, breed susceptibility and knowledge of the presence or absence of the gene in the pig.

Control/Prevention

  • Treatment is usually ineffective.
  • Sprinkle the pig with cold water to control its increasing temperature.
  • Inject 50-100 ml of calcium gluconate intramuscularly at two different sites.
  • Give a tranquilizer.
  • Do not move the animal, or cause unnecessary muscle activity.
  • Avoid stress in pigs.
  • Select breeding animals, specially boars; confirm negative for the gene.
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