What is Capture Myopathy?
Sometimes called “cramp”, “exertional myopathy”, or “capture disease”, this syndrome is a cause of paralysis or inability to fly in birds – usually after a capture or handling event. Long-legged birds such as wading birds and cranes were thought to be most commonly affected, but the problem has been found in a wide range of species, from songbirds to hawks and seabirds.
What does it look like?
An inability to walk or fly, stiffness, weakness, or signs of paralysis are common presenting signs in affected birds – it may happen immediately after capture, or it could start to show signs some hours (or even days!) later. The signs may improve if the condition is mild or get worse in severe cases. Some birds will collapse or even die quickly or may have a prolonged period in care. If capture myopathy is suspected, the bird should always be taken to a vet, wildlife hospital or experienced wildlife rehabilitator for assessment.
What causes capture myopathy?
Acute stress, struggling, or extreme exertion due to pursuit (or entanglement, such as in nets) can all lead to muscle damage. Muscles become stiff, but in severe cases, the muscle starts to break down and releases breakdown products into the bloodstream, affecting the heart and kidneys. Similar syndromes in humans and mammals usually lead to kidney failure, but this doesn’t seem to be the case in birds. However, birds will often succumb to secondary dehydration or starvation if not treated appropriately.
How do you know for sure what is the problem?
Presumptive diagnosis is based on the symptoms and recent history, but in a vet clinic, significant changes can be seen in blood biochemistries, including the elevation of muscle enzymes Creatine Kinase (CK) and Aspartate Aminotransferase (AST). These may increase tens- or even hundreds- of thousands of times higher than normal.
Is it possible to treat capture myopathy?
The short answer is yes.
Treatment of myopathy can be time-consuming and costly but has been successful in some cases. Fluid therapy, supportive care, physiotherapy and good nutrition are essential treatments. Medications such as non-steroidal anti-inflammatories and muscle relaxants may have additional benefits in treatments. If birds have paralysed legs, then sling therapy can be beneficial - where birds can relieve pressure on their chest for a few hours and slowly put weight back onto their legs as they gain strength. Rehabilitators should be aware that it may take several weeks for muscles to heal and for the bird to regain full function, so they should be committed to providing a full course of treatment before beginning. Also make sure birds are in good body condition and are fully waterproof (if waterbirds) before releasing back to the wild.
Prevention is better than cure, so keep capture myopathy in mind before pursuing a bird in the wild and pay attention to reducing the time a bird is trapped in a net when catching. If a bird has been trapped in netting in an orchard or otherwise, muscle damage should be considered, and the bird should be treated with fluid therapy and supportive care until you are sure it is recovered enough for release. If in doubt, always seek advice!
Ward, J.M., Gartrell, B.D., Conklin, J.R. & P.F. Battley. "Midazolam as an adjunctive therapy for capture myopathy in bar-tailed godwits (Limosa lapponica baueri) with prognostic indicators." Journal of Wildlife Diseases 47.4 (2011): 925-935.
Written by Dr Janelle Ward
Wildlife Veterinarian and Co-Founder of Learn Bird Care Ltd
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