Porcine stress syndrome
Porcine stress syndrome, also known as Malignant hyperthermia or PSS, describes the condition in pigs. It is an inherited, autosomal recessive disorder due to a defective ryanodine receptor leading to huge calcium influx, muscle contracture and increase in metabolism.
This can be triggered by stress, under anaesthesia with halothane or during intense exercise.
PSS may appear as sudden death in pigs, often after transport.
PSS can also occur in pigs being anaesthetised under halothane for certain procedures, although this is rare.
Finally, PSS can manifest itself in the abattoir 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, 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.
Clinical signs and diagnosis
Pigs may be found partly alive and partly dead on arrival after transport.
Initial signs of the onset of PSS are pyrexia, 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.
Treatment and control
Often it is impossible to avoid the periods of stress that pigs will experience. Sedation and glucocorticoids may be beneficial.
Under anaesthesia, dantrolene 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 rarely seen these days.
Stress at slaughter should be minimised in all cases.
References
- Porcine Stress Syndrome expert reviewed and published by Wikivet accessed 09/10/2011.