TWENTY-THIRD ANNUAL EASTERN FISH HEALTH WORKSHOP JOHN CARVER INN, PLYMOUTH, MA 30 MARCH - 2 APRIL, 1998 Stress And The Stranded Marine Mammal David St. Aubin Director of Research and Veterinary Services, Mystic Aquarium, Mystic, CT Marine mammals strand for a host of reasons, most of which leave them in a debilitated condition. Though agents such as toxins and certain viruses can kill acutely, other factors including parasitic and bacterial infections are more gradual, and may flourish as opportunistic secondary invaders in compromised animals. While dealing with such infections, an animal may be unable to forage adequately, and malnutrition further complicates the clinical picture. By the time it arrives in the hands of a rescue team, problems may have evolved to a point that it is difficult to reconstruct the development of its condition. Nevertheless, medical care staff must quickly determine what steps are needed to start the animal on the road to recovery. At the rehabilitation center, the strander's condition is evaluated through a detailed physical examination and a series of tests involving blood collection, microbiological culture and parasite screens. Antibiotic therapy may be instituted sometimes without knowing the exact nature or site of infection, but relying on reasonable assumptions about the organisms that may be involved. During early critical care, it is appropriate to assume that the animal is stressed and to respond accordingly. The stress response in marine mammals has characteristics that are shared with other mammals, and at least one that appears selectively developed to a greater degree than in terrestrial counterparts. Laboratory studies on pinnipeds and cetaceans revealed a suite of hematological and plasma chemical changes following adrenal stimulation with adreno-corticotropic hormone (ACTH). Cortisol, the primary glucocorticoid, is a good indicator of an adrenal response in pinnipeds but not in cetaceans. Yet, physiological and hematological effects of glucocorticoid release are evident in both groups, suggesting important differences in plasma levels of the active free hormone. Excessively elevated cortisol levels in cetaceans signal impaired hepatic clearance associated with circulatory disturbances and shock. Both groups show an unusual sensitivity for ACTH-stimulated release of the mineralocorticoid aldosterone. This common adaption appears beneficial in managing fluid and electrolyte balance during times of stress. Stranded marine mammals often show evidence of iron imbalance, as a consequence of dehydration or through possible inappropriate or prolonged secretion of mineralocorticoid. The need to monitor and redress such imbalances can be critical to the survival of stranders during the early stages of their treatment.   Return to 23rd Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page