Porcine Hyperthermia Study Guide

Overview and Clinical Importance

Hyperthermia in swine encompasses a spectrum of conditions characterized by dangerously elevated body temperature due to either environmental heat stress or genetic susceptibility. The two primary conditions are Porcine Stress Syndrome (PSS), also known as Malignant Hyperthermia (MH), and environmental heat stroke. These conditions are critical for NAVLE examination as they represent both animal welfare concerns and significant economic losses in the swine industry due to mortality and poor meat quality (pale, soft, exudative or PSE pork).

Pigs are particularly susceptible to hyperthermia because they have poorly functional sweat glands, thick skin, and often substantial subcutaneous fat layers that limit heat dissipation. The thermoneutral zone for adult pigs is typically between 16°C and 22°C (61-72°F).

Etiology and Classification

Classification of Porcine Hyperthermia

Genetics and Pathophysiology

The RYR1 Mutation

Porcine Stress Syndrome is caused by a point mutation in the RYR1 gene (Ryanodine Receptor 1), which encodes the calcium release channel in the sarcoplasmic reticulum of skeletal muscle. The specific mutation is R614C (Arg615Cys), where arginine is replaced by cysteine at position 615. This mutation is inherited in an autosomal recessive pattern in swine (unlike humans where it is autosomal dominant).