Abstract

Tranquilization of 12 dolphins from 96 to 279 kg with diazepam allowed use of specialized dentistry and ophthalmic equipment. An oral dose range of 0.26 to 0.36 mg/kg provided control sufficient to allow infiltration of local anesthetic into and around the periodontal tissues. Ophthalmic procedures well tolerated included indirect ophthalmoscopy, applanation tonometry and measurement of corneal curvature (keratography). A "reverse goggle" developed for the study allowed the use of a kowa RC-2 fundus camera to obtain ocular fundus pictures of the living cetacean for the first time. All physiological parameters monitored during each procedure remained within normal limits.

Introduction

The aquatic environment makes it difficult to properly examine the eyes and/or teeth of dolphins in a clinical or research setting. It is inadvisable and virtually impossible to force open the eyelids of a cetacean.(1)

The dolphin has a unique mammalian eye that has received much attention in recent years.(2,3) The cornea is the interface between the dolphin's eye and its environment. The rear of the eye, the fundus, contains vascular and neural structures not seen before in a living cetacean.

Mandibular anesthesia,(4) especially for tooth extractions from the maxilla was not satisfactory. It is difficult to infiltrate local anesthesia around cetacean teeth with a regular syringe and needle as used for the mandibular nerve block.

The use of diazepam as a tranquilizing agent allowed the application of specialized instruments during the performance of research and clinical procedures, on the eyes ant teeth of dolphins.

Materials and Methods

The eight Tursiops truncatus and one Grampus griseus used in these studies were housed in open ocean pens in Kaneohe Bay, Hawaii. The Bottlenose dolphins were from three to twenty years old and weighed from 96 to 179 kg, the Risso's dolphin was nine years old and weighed 279 kg.

Two hours before tooth extractions or eye examinations 0.26 to 0.36 mg/kg of diazepam was administered per os. After a two hour wait, each animal was brought into the laboratory which allowed controlled light and temperature throughout the procedures. Before during and after each procedure blood samples were collected and during the procedures temperature pulse and respiratory rates were monitored and recorded.

For dentistry, a local anesthetic was injected toward the mandibular foramen lateral to the base of the tongue.(4) In addition, local anesthetic was injected using a stainless steel "PDL" intraligamentary anesthetic syringe (Special Products Inc., 102 Western Ct., Santa Cruz, CA 95060) into the infraalveolar nerve and periodontal tissue around each tooth to be extracted.

The source of catoptric images for corneal keratography was a uniformly back-illuminated disc of translucent plastic onto which group of concentric rings had been painted in six black/white cycles. After the application of Opthane (E.R. Squibb and Sons, Inc., PO Box 4000, Princeton, N.J. 08540), an applanation tonometer was applied to each cornea and intraocular pressures measured.

Mydriasis was obtained by the application of two to three drops of a 2.5 ophthalmic solution of Neo-Synephrine (Winthrop Laboratories, 90 Park Avenue, New York, NY 10016) to each eye. A "reverse goggle" was attached periorbitally with marine grease and photographs were obtained using a Kowa RC-2 fundus camera. The goggle was made from a plastic Petri dish 14cm in diameter and 1.5 cm deep, with a hole cut out for the eye and a port added for the inflow of sea water or sterile saline.

Results

Table 1. Dose Range of Diazepam and Physiological Measurements During Three Hour Dental/Ophthalmic Procedures

Physiological parameters monitored from two hours after the administration of Diazapam to the end of each procedure (Table 1) indicate good control, Results of analysis of complete blood counts and a panel of 20 blood enzymes and ions were all within the limits established as normal for each individual animal.

On one occasion it became necessary to administer Diazepam intravenously to a 125kg dolphin 30 minutes after the start of the ophthalmic examination. She had received 0.33mg/kg diazepam three hours prior to the start of the exam. The IV dose was 0.08mg/kg and provided adequate control to continue.

Dentistry

Oral administration of Diazepam followed in two hours by a mandibular nerve block and injection of local anesthetic around mandibular and maxillary infraalveolar nerves was effective (Table 1) for five dental procedures in which five to 48 teeth were extracted.

Ophthalmology

Indirect ophthalmoscopy and fundus photography were possible using tranquilized dolphins. A montage of the photographs was constructed showing the white head of the optic nerve (papilla) approximately in the geometric center of the bright yellow, totally tapetalized fundus. Also observed was a remnant hyloid vessel, a peripapillary ring and a nearly symmetrical vascular tree. Features of the Grampus ocular fundus were similar to Tursiop except for coloration and density of the vascular tree.

The usual secretions from the eye of the dolphin were too tenacious to be totally washed away so kertatograms were possible but high image quality was never achieved. Numerous small optical irregularities of the corneas were noted.

Intraocular pressures ranged from 18 to 80mm Hg for the Bottlenose dolphins and 17 to 24mm Hg for the Risso's dolphin.

Each animal was closely monitored upon return to their ocean pen. With one exception activity was normal and the dolphins accepted food. The dolphin that received the intravenous dose was slightly disoriented upon her return to water. That condition cleared up within two hours.

Discussion

During the delivery of health care to exotic animals it becomes necessary to restrain them for certain procedures or examinations. It is essential to use the most stress free and safest methods available. Cetaceans, because of many adaptations to their aquatic environment, have specialized needs and are of particular interest to investigators. We have used a tranquilizer that is easy to administer, has a wide range of safety and provides very effective control of small cetaceans during clinical and research procedures.

Use of diazepam at the reported dose levels with attention to the proper time interval provided us with the control necessary to safely bring dolphins into our laboratory for dental work essential to their good health.

An additional benefit of this practice was to allow experimental protocols leading to new knowledge of the dolphin eye.(5,6) Further studies are necessary to confirm the high intraocular pressures recorded from Tursiops eyes and to determine significance of differences between the eyes of dolphins and terrestrial mammals.

References

1.  Geraci, J.R., J. Sweeney, Clinical Techniques. In: Zoo and Wild Animal Medicine, (ed) M.E. Fowler, W.B. Saunders Company 580-587 (1978)

2.  Dawson, W.W., The Cetacaean Eye. In: Cetacean behavior, mechanisms and functions, (ed) L.M. Herman. Wiley Interscience, NewYork, 54-99 (1980)

3.  Dral, A.D.G., On the retinal anatomy of cetacea. In: Functional anatomy of marine mammals. (ed) R.J. Harrison Academic Press, London, vol 3, 86,87 (1977)

4.  Ridgway, S.H., R.F. Green, J.C. Sweeney, Mandibular anesthesia and tooth extraction in the bottlenosed dolphin. J. of Wildlife Diseases, 11, 415-475 (1975)

5.  Dawson, W.W., J.P. Schroeder, S.N. Sharpe, Corneal surface properties of two marine mammal species. Submitted to Marine Mammal Science. (1986)

6.  Dawson, W.W., J.P. Schroeder, J.F. Dawson, The ocular fundus of two cetaceans. Submitted to Marine Mammal Science (1986)