Abstract

The cetacean musculoskeletal system is uniquely designed for constant swimming activity and a range of diving ability. Muscle disease in cetaceans may involve a wide variety of presentations and can include abnormalities related to injury, overexertion, infections, medication administration, and inflammatory disease (myositis). Lesser known conditions seen in humans have not been well documented in cetaceans but may include muscular dystrophies, genetic, metabolic and endocrine based etiologies. Bone or skeletal abnormalities (osteopathy) include a long list of possible etiologies with similar general categories such as infection, injury, genetic disorders and abnormal growths such as tumors and cysts. The cetacean clinician may deal with a much shorter list of these system problems than human medical personnel, but these conditions present a challenge for diagnosis and therapy.

Stranded cetaceans often develop spinal abnormalities such as scoliosis and kyphosis secondary to stranding events though one animal stranded with a severe lateral displacement. Similar conditions have been observed in free-ranging cetaceans as well as animals in controlled environments. The clinical evaluation should, when possible, include imaging, CBC, chemistries, sedimentation rate, and fibrinogen levels to better understand the relationship of diagnostic findings to the current state of the anomaly. The value of some tests may be enhanced when sampling at or near the beginning of the condition. Imaging may include CT, MRI and ultrasound, the latter being available more often than the former techniques to many clinicians. While the abnormal alignment of the spinal column is the most visually obvious finding, muscle damage or deterioration is often the major factor leading to these conditions. Muscle biopsies of the affected area may be indicated. In some cases skeletal deformity and misalignment may not be visually apparent and animals may show reluctance to engage in difficult or high energy behaviors, suggesting the need for skeletal imaging. Stranded cetaceans may develop spinal curvature days after the rescue event. Factors associated with these changes may include physical trauma, myositis, overexertion, acidosis, tissue hypoperfusion, and mineral imbalance. Treatment protocols that have reduced post stranding curvature include on beach medications as well as muscle-based post stranding therapy. On-site medications have included vitamin E-selenium combinations given intramuscularly, based on the selenium component, and calcium supplementation initially given IM. Follow-up with oral vitamin E and calcium for 3 weeks minimum appears to be beneficial as does pain relief. Most important in avoiding serious deformity or affecting the early stages is the encouragement to begin reusing muscles in a normal dorsal ventral movement with a straight swimming pattern rather than a circular pattern. Small circular pools appear to limit clinical improvement and enhance curvature. Where lateral curvature is already present, treatment may include electromyostimulation to aid in contraction of the muscles of the opposite side of the concavities. Wild free swimming cetaceans have also been found with spinal deformities illustrating additional causes of this condition such as injury or developmental involvement. Dolphins in small pools undergoing extended care may develop scoliosis and will respond to supplementation and reestablishing straight swimming.