Porcine stress syndrome

Porcine stress syndrome is a genetic condition that causes sudden death and a pale, soft, exudative muscle resulting in dark, dry and hard flesh.

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


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 flesh; and necrosis of the dorsal muscle. Pigs with great development of muscles are more likely to have the gene. The pig can be homozygous (susceptible), heterozygous or free of the gene (both not susceptible). The gene can be identified due to a response to the halothane gas (an anesthetic), but recent researchers have developed a genetic probe 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 muscular activity it undergoes a change in the metabolism of muscles, going from aerobic to anaerobic, also developing biochemical abnormalities. Body tissues become acidic and there is a significant increase of temperature, up to 42 ° C.



All ages

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


Causes / Contributing Factors

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



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



  • The treatment is usually ineffective.
  • Sprinkle the pork with cold water to control the 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.

Atlas of pathology

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