Porcine stress syndrome, also known as

malignant hyperthermia Malignant hyperthermia (MH) is a type of severe reaction that occurs in response to particular medications used during General anaesthesia, general anesthesia, among those who are susceptible. Symptoms include tetany, muscle rigidity, hyperthermia ...

or PSS, is a condition in pigs. It is characterised by

hyperthermia Hyperthermia, also known simply as overheating, is a condition in which an individual's body temperature is elevated beyond normal due to failed thermoregulation. The person's body produces or absorbs more heat than it dissipates. When extreme ...

triggered by stress, anaesthesia with

halothane Halothane, sold under the brand name Fluothane among others, is a general anaesthetic. It can be used to induce or maintain anaesthesia. One of its benefits is that it does not increase the production of saliva, which can be particularly useful i ...

or intense exercise. PSS may appear as sudden death in pigs, often after transport. It is an inherited,

autosomal recessive In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and t ...

disorder due to a defective

ryanodine receptor Ryanodine receptors (RyR for short) form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons. There are three major isoforms of the ryanodine receptor, which are found in different tissu ...

leading to huge calcium influx, muscle contracture and increase in metabolism. PSS can manifest itself in the

abattoir A slaughterhouse, also called abattoir (), is a facility where animals are slaughtered to provide food. Slaughterhouses supply meat, which then becomes the responsibility of a packaging facility. Slaughterhouses that produce meat that is no ...

as the production of Pale, Soft and Exudative meat due to a rapid fall in muscle pH and degradation of muscle proteins and structure. This meat is usually rejected after inspection. This disorder is most common in

Landrace A landrace is a domesticated, locally adapted, often traditional variety of a species of animal or plant that has developed over time, through adaptation to its natural and cultural environment of agriculture and pastoralism, and due to isolation ...

, Piétrain and crossbreeds of these breeds of pig. The genes may have been favoured in the past due to a larger muscle bulk in these breeds. However this is not standard protocol in developed countries these days. PSS Breeding Practices

Clinical signs and diagnosis

Truckloads or railcar loads of PSS-susceptible pigs may be found with a higher-than-average percentage dead on arrival after stressful events such as transport. Initial signs of the onset of PSS are

pyrexia Fever, also referred to as pyrexia, is defined as having a temperature above the normal range due to an increase in the body's temperature set point. There is not a single agreed-upon upper limit for normal temperature with sources using val ...

, panting, sweating, tachycardia and arrhythmias. Chronic cases may show muscle atrophy. Under halothane anaesthesia, pigs will suddenly become rigid and pyrexic. The halothane challenge was the historical method of diagnosis. Genetic testing via a PCR enables affected and carrier animals to be found. Psychologist Melanie Joy has likened PSS to

post-traumatic stress disorder Post-traumatic stress disorder (PTSD) is a mental and behavioral disorder that can develop because of exposure to a traumatic event, such as sexual assault, warfare, traffic collisions, child abuse, domestic violence, or other threats on ...

in humans.

Treatment and control

Removing the pig from the stressful situation can prevent the episode.Porcine Stress Syndrome
expert reviewed and published b
Wikivet
accessed 09/10/2011. Sedation and

glucocorticoids Glucocorticoids (or, less commonly, glucocorticosteroids) are a class of corticosteroids, which are a class of steroid hormones. Glucocorticoids are corticosteroids that bind to the glucocorticoid receptor that is present in almost every vertebr ...

may be beneficial. Under anaesthesia,

dantrolene Dantrolene sodium, sold under the brand name Dantrium among others, is a postsynaptic muscle relaxant that lessens excitation-contraction coupling in muscle cells. It achieves this by inhibiting Ca2+ ions release from sarcoplasmic reticulum s ...

sodium is a very effective treatment. Genetic testing enables animals to be removed from the herd if they are positive for the gene. This means that the disorder is rare in the developed world these days. Stress at slaughter should be minimised in all cases.

References

Swine diseases Syndromes in mammals {{Veterinary-med-stub