Abstract

Thirteen free-ranging adult crabeater seals (Lobodon carcinophagus) were immobilized during October 1997 with combinations of pethidine hydrochloride (150 mg/ml solution) and midazolam hydrochloride (20 mg/ml solution) given by i.m. injection via dart. Both drug solutions were prepared from pure substance at the Royal Hobart Hospital, Hobart, Tasmania. Weights of animals were estimated and a state of light anesthesia was the desired level of immobilization. Initial doses of pethidine administered ranged between 1.29–2.2 mg/kg and midazolam between 0.29–0.37 mg/kg. Four animals required supplemental doses of anesthetic agents in order to achieve adequate immobilization. These were delivered intramuscularly by hand injection 30–35 min after initial drug administration. Of these animals, one received only midazolam at 0.16 mg/kg while the other three received pethidine and midazolam at doses of 0.31–0.58 mg/kg and 0.15–0.16 mg/kg respectively. There was one mortality which occurred in an animal that received a supplemental dose of pethidine (0.42 mg/kg) and midazolam (0.15 mg/kg). All other animals were revived using 0.5 mg flumazenil (Anexate, Roche Products, Australia) and 4 mg naloxone (Narcan, Boots Company, Australia) given intramuscularly by dart or hand injection or intravenously into the extradural venous sinus. Time to initial recovery was defined as the ability to move in a coordinated fashion. For animals that received antagonists intramuscularly this ranged from 4–11 min. Animals receiving antagonists intravenously recovered in 1–2 min.

Blood samples were collected from the extradural venous sinus of six animals, placed in plain and EDTA tubes and maintained at 10°C until processing within 4 hr of collection. Blood films were stained using the May-Grunwald Giemsa method. White cells were counted in 10 fields, a mean number of cells per field calculated, and from this an estimated white cell count was calculated. Differential white cell counts were performed manually. Microhematocrit tubes were spun at 1200 revolutions/min before the PCV was read. PCV values ranged between 41–52% and estimated total white cell counts were between 7–13x10⁹/L. Neutrophils ranged between 69–81%, lymphocytes 9–23%, monocytes 2–7% and, eosinophils 0–4%. Serum collected was frozen in liquid nitrogen for less than 4 wk until biochemical analysis. Serum biochemistry parameters measured were total protein, albumin, globulin, sodium, potassium, chloride, bicarbonate, urea, creatinine, calcium, phosphorus, glucose, cholesterol, total bilirubin, ALP, ALT, GGT, AST, CPK, and LDH. All were similar to those reported for other pinniped species.^1-3

All blood samples were tested for their ability to neutralize canine distemper virus, phocine distemper virus-1, porpoise morbillivirus, dolphin morbillivirus and phocine herpes virus-1. Three seals had neutralizing antibodies to morbillivirus that in two animals were probably induced by a canine distemper-like virus. One seal had virus-neutralizing antibodies to phocine herpesvirus-1. All blood samples were tested by ELISA for antibodies to influenza A, Mycobacterium bovis, and M. avium. No antibodies to these agents were detected.

Literature Cited

1.  Bossart GD, LA Dierauf. 1990. Marine mammal clinical laboratory medicine. In: Dierauf LA, ed. CRC Handbook of Marine Mammal Medicine: Health, Disease and Rehabilitation. CRC Press. Boca Raton, Florida.

2.  Medway W, JR Geraci. 1993. Clinical pathology of marine mammals. In: Fowler ME, ed. Zoo and Wild Animal Medicine. vol. W B Saunders Company. Philadelphia.

3.  Roletto J. 1993. Hematology and serum chemistry values for clinically healthy and sick pinnipeds. J Zoo Wildl Med. 24: 145–157.