Capture myopathy is a condition affecting wild animals, often during capture, handling, or transport, that can lead to severe muscle damage and organ failure. It presents a substantial challenge in wildlife conservation and management efforts globally, as it can result in significant illness and death. This non-infectious metabolic disease arises from intense stress and physical exertion.
Understanding Capture Myopathy
When a wild animal experiences extreme stress or exertion, its body initiates a “fight or flight” response. This response involves the rapid release of stress hormones like adrenaline and noradrenaline, which prepare the animal for intense physical activity. The increased metabolic demand on the muscles quickly depletes oxygen reserves, forcing the body to switch from aerobic (oxygen-using) to anaerobic (without oxygen) metabolism.
This shift to anaerobic metabolism leads to a rapid buildup of lactic acid in the muscles, causing metabolic acidosis (a significant drop in pH). Lactic acid and other metabolic byproducts damage muscle cells, leading to rhabdomyolysis. As muscle cells break down, they release myoglobin and creatine kinase into the bloodstream. Myoglobin can overwhelm the kidneys, causing acute kidney injury, potentially leading to death. Widespread tissue damage, electrolyte imbalances, and cardiac issues like arrhythmias can lead to organ failure and a poor prognosis.
Recognizing the Signs
The signs of capture myopathy can manifest acutely, immediately or within hours of a stressful event, or they can be delayed, days or weeks later. Acute signs often include rapid breathing (tachypnea), an elevated heart rate (tachycardia), and a high body temperature (hyperthermia). Animals might also exhibit muscle tremors, weakness, or an unsteady gait (ataxia), sometimes progressing to collapse.
With delayed symptoms, animals may initially appear normal. Delayed signs can involve lameness, stiffness, or partial paralysis, especially in the hind limbs. Dark, reddish-brown urine (myoglobinuria) is another common indicator of muscle breakdown and potential kidney involvement. Animals might also show depression, lack of responsiveness, or reluctance to move. Severe cases often lead to organ failure and death.
Minimizing the Risk
Preventing capture myopathy is the most effective approach, given the unfavorable outcome once symptoms appear. Thorough planning of capture operations is important, considering species, environmental conditions, and capture methods. Minimizing the duration of pursuit, handling, and transport reduces stress and exertion on the animal. Using appropriate chemical immobilization agents can reduce fear, relax muscles, and prevent hyperthermia during capture.
Reducing sensory stimuli, such as loud noises and visual disturbances, during handling helps keep stress levels low. Adequate hydration and cooling measures, especially in warmer temperatures, can mitigate hyperthermia, which exacerbates the condition. Experienced personnel, proficient in efficient handling techniques, play a significant role in minimizing the animal’s time under duress. Post-capture monitoring allows for early detection of emerging signs, though prevention remains the primary focus.
Caring for Affected Animals
Managing capture myopathy primarily involves supportive care, as there is no specific cure for the underlying muscle damage. Fluid therapy combats dehydration, supports kidney function by flushing myoglobin, and corrects metabolic acidosis. Pain management with analgesics alleviates discomfort from muscle trauma, while muscle relaxants may reduce muscle spasms.
Anti-inflammatory drugs address systemic inflammation. Vitamin E and selenium supplementation are considered for antioxidant properties, though their definitive role in treatment or prevention is still being studied. The prognosis for severe capture myopathy is generally poor, particularly in field settings with limited intensive monitoring and treatment options. Survivors often face long recovery periods, lasting disabilities, or succumb to delayed complications like heart failure.