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

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.

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).

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

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

• 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.