Abstract

On November 14, 2011, a 421.8-cm total length, approximately 135-kg female neonatal killer whale (Orcinus orca) was found beach cast and dead near Seaview, Washington State. The carcass was collected by Northern Oregon Southern Washington Marine Mammal Stranding Network and transported to Portland State University for necropsy. The animal was in good postmortem (code 2) and fair body condition. Bilateral fetal folds (6 left/4 right), mild right curvature of the dorsal fin and flukes, and rostral vibrissae (3 left and 3 right) were apparent. There was a 2-cm umbilicus stalk that was moist and oozed a small amount of dark red clear serous fluid. The animal was estimated to be 1–2 days old and determined to be an offshore ecotype. The eyes were closed and the saddle patch was poorly defined. The umbilical veins and arteries were patent with a small amount of clotted blood within the lumen of the vein. The foramen ovale and ductus arteriosus were patent, and no teeth had erupted. The internal and external aspects of the umbilicus appeared normal. The thymus was 10 x 15 cm in size and within the cranial mediastinum.

The most salient gross finding was marked segmental dilation of the caudal thoracic esophagus with pronounced dilation of the esophageal hiatus. The lungs were displaced cranially and compressed. On incision of the esophagus at the level of the diaphragm, there was partial eversion glandular gastric compartment into the proximal esophagus and the involved mucosa was 12–15 cm in diameter, friable to mucoid and dark red. There was moderate edema of the affected area. Within the distal glandular compartment, there was a moderate amount of bright yellow tenacious material interspersed within rugae and adherent to the mucosa. Extending distally from the esophagogastric junction, there were numerous multifocal and circumferential mucosal erosions and ulcerations with abrupt and mildly hyperemic margins. There was marked lymphadenopathy of the regional lymph nodes, which were dull grey white and bulged on sectioned surface. Marked splenomegally was noted. Along the lateral aspect of the torso, at the level of the anus, there were scattered foci of tan yellow friable muscle. CT scan of the head disclosed abundant amorphous soft tissue attenuating material associated with the right bulla and sinus and on dissection, the area was a large cavity that contained slightly turbid white grey fluid.

Histopathology revealed moderate aspiration and squames and meconium and focal myocellular degeneration and necrosis with lymphohistiocytic infiltrates and scattered dystrophic mineral deposition. Protein electrophoresis disclosed a gamma globulin level of 0.3 g/dl, consistent with a failure of passive immunization. No significant bacteria were recovered from sampled tissues.

Based on review of stranding demographics (Barbieri et al, in-prep manuscript), most killer whale mortalities are either in geriatric or neonatal age classes. Despite aggressive efforts to recover and necropsy stranded individuals, there is still a paucity of information regarding disease conditions which may adversely impact neonatal and juvenile animals. In this animal, the proximate cause of death is attributed to the gastric herniation, which likely impeded the ability of the animal to ingest colostrum. Brucella spp. antibodies have previously been documented in postmortem heart blood of stranded killer whales and have caused abortion in bottlenose dolphins; however, the contribution of this pathogen to neonatal loss is unknown.

Acknowledgements

We thank the volunteers and staff of the Portland Marine Mammal Stranding Network, Washington Department of Fish and Wildlife, Cascadia Research Collective and NOAA Fisheries for their assistance with stranding response and sample collection. This work was supported with funding from the John H. Prescott Marine Mammal and Rescue Assistance Grant and NOAA Fisheries.

References

1.  Barbieri M, Raverty S, Hanson M, Venn-Watson S, Ford JK, Gaydos J. A retrospective analysis of killer whale strandings in the North Pacific Ocean and the benefits of a coordinated stranding response protocol. Draft.