California Potbellied Pig Association, Inc

Porcine Stress Syndrome


(malignant hyperthermia)

Potbellied pig owners may have cause for concern. Porcine stress syndrome (PSS), a potentially life-threatening genetic disease, thought only to affect commercial swine, has recently been found in the genes of at least one potbellied pig.  PSS is a syndrome of acute death, and signs may include progressive breathing problems, tremors and stiffness, and high body temperature.  The disease causes incorrect calcium transport to muscles, which creates an excess of lactic acid as well as a high temperature.  Both symptoms can be fatal. In livestock pigs, the disease usually is onset after transportation, and due to fighting, exercise and even a hot climate.  One potbellied pig has already died from the disease and another pig, suspected of dying from PSS as well, is being tested. According to the Duchess Fund, an organization that provides medical information about potbellied pigs to the public, the first pig, known as "Case A," died during a spay procedure and a DNA test revealed the pig had PSS.  "Case B" also died during a spay, but no fresh blood was available so the parents are being tested.  The mother was negative for PSS, or malignant hyperthermia as it is also called, and the test results of the father pig are pending, said Barbara Baker of the Duchess Fund.

PSS has long been known as a genetic disease in commercial swine that is promoted by overgrown muscles and stress.  As of yet, there is no way of knowing if Case A was an isolated incident or if the PSS gene is widespread in potbellied pigs.  "They’ve bred it out of commercial swine," Ms. Baker said. In fact, commercial breeders were able to breed the gene out of the pigs fairly easily, added Barbara Straw, DVM, Ph.D.  "It is controlled at a single gene," Dr. Straw explained.  "This gene is associated with heavy muscling.  "Potbellied pigs are often kept as companion animals and how the disease got into their gene pool so far is a mystery. The pigs are not bred for food and so their muscles are not overly developed.  PSS can be brought on, however, by anesthesia, which is what happened in Case A.  Potbellied pig owners may be concerned because if their pig has the PSS gene, it might die from a simple procedure requiring the use of anesthesia, such as a spay or tusk trimming, Ms. Baker said.  If a pig was known to have PSS, Ms. Baker said, "you would certainly want to limit the procedures down."  For example, a pig with PSS might not have its tusks trimmed as often as a pig without the gene.  A drug called Dantrolene can be used to stop a PSS attack, Ms. Baker, said but few veterinarians carry it since PSS had never been known to affect potbellied pigs.  Dr. Straw said she doesn’t think the disease is widespread among potbellied pigs; if it were, more pets would have died during spays.  It should be just as easy to breed the gene out of potbellied pigs as it was to remove the gene from the commercial pigs’ pool, but since only one case of PSS has been confirmed, this may not even be necessary, Dr. Straw said. "It may be that very few carry this trait," she said. Even the pigs that do have the gene do not always get PSS. "Most of them get along without having an episode."    

To find out if your potbellied pig has the PSS gene, you can order a special test kit from GeneScreen, a genetic testing laboratory. The kit costs $33 (or $25 if you pre-register with Swinetics at 877-440-0894) and contains instructions and a blood absorbent card. Once the card containing a drop of the pig blood is mailed back, it takes five days to get the results.

"The paradise of my fancy is one where pigs have wings." 

G. K. Chesterton