Abstract

Marine mammals both in the wild and those kept under human care are exposed to environmental challenges, which may serve as stressors, potentially affecting the animal's immune system. These challenges can include environmental pollutants such as oil, industrial toxins, and noise, changes in water and air temperature, changes in housing conditions, social interactions, transport, and novel training regimens. The above challenges have been shown to cause activation of the autonomic nervous system and changes in immune function in other mammals such as rodents, sheep, cattle, and humans.

Previous studies from our laboratory have shown evidence for a bidirectional communication between the nervous and immune systems in cetaceans, with postganglionic nerve fibers forming close associations with cells of the immune system in lymphoid organs; the presence of beta adrenergic receptors on cetacean lymphocytes; and functional changes of lymphocytes in vitro after exposure to neurotransmitters. Therefore, we have initiated studies to investigate the potential effects of environmental challenges on autonomic nervous system activation and immune function of marine mammals.

Navy cetaceans serve as a benchmark population to carry out these studies given the extensive life history information we have on the animals, the ability to look at the entire inventory which includes animals of all ages and both genders, and the proximity of the research laboratory to the animals, allowing for quality control and immediate processing of the samples.

Presently, we are gathering baseline data. Measurements include indicators of nervous system activation and immune function. In addition we have initiated studies on the effects of transport, exposure to cold water, loud noise, social interactions, and introduction to novel environment on some animals. The same parameters are being measured for ill and pregnant cetaceans with the hope of revealing additional parameters for clinical evaluation and care.

Future studies will focus on counteracting any adverse effects of challenges by measuring the potential therapeutic effects of adrenergic agonists/antagonists, vaccines, and immune system boosters, etc. Findings from these studies will not only help to maintain health in Navy marine mammals but will also increase our understanding on the effects of environmental challenges for marine mammals in the wild.

Acknowledgements

This work was supported by a grant from the Office of Naval Research (N00014-00-1-0041). The authors wish to thank Lee Berk and Lily Tran (Loma Linda University), Jeff Stott (UC Davis), Brett Davis (ARUP, Laboratories), Scott Steinert and Becky Streib Montee (SPAWARSYSCEN), Rhonda Patterson and Bobby Middlebrooks (USM), Carolyn Schlundt Melka (SPAWARSYSCEN), Lee Asnin and the hospital staff at SEARCH in Sitka, AK and the veterinary and training staff of the Navy Marine Mammal Program.