Judy S.L. Leger, DVM, DACVP
There was an unusual cluster of unexpected mortality in Emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliae) penguins during a 4-month period from November 2001 to March 2002. Two emperor and three Adélie penguins all presented with sudden death. The affected birds ranged from 16–25 years. Sex distribution was two male emperors and one male and two female Adélies.
On gross examination, four of the five birds had a large amount clotted blood around the great vessels and the heart base. One bird had an extensive pericardial hemorrhage with both clotted and unclotted blood distending the pericardium and compressing the heart. Full thickness aortic tears ranging from 0.5–1 cm in length were identified in the proximate aorta of all birds. No birds had evidence of aortic dilation or aneurysm. One bird had firm intimal plaques.
Histologic examination revealed cystic medial necrosis and acute hemorrhage in the aortic wall at the site of the tears and extending into the adjacent wall, primarily within the tunica media. Special stains for elastin demonstrated fragmentation and rupture at the site of hemorrhage but when performed in nonhemorrhagic areas adjacent to the area of rupture these stains demonstrated no significant fiber shortening or fragmentation. The one emperor with intimal plaques noted grossly did have significant multifocal atherosclerotic changes including mineralization in the aortic wall.
Heavy metal analysis was performed on the livers from three of these birds. Copper levels were within published normal values for these seabirds,2,3 but also within the ranges associated with aortic rupture in turkeys and ostrich.1
The etiology of this mortality cluster was not determined. The low hepatic copper in two birds suggests a possible role of copper deficiency. The temporal cluster suggests a secondary factor.
1. Graham, C.L. 1977. Copper levels in livers of turkeys with naturally occurring aortic rupture. Avian Dis. 21:113–116.
2. Keymer, I.F., H.M. Malcolm, A. Hunt, and D.T. Horsley. 2001. Health evaluation of penguins (Sphenisciformes) following mortality in The Falklands (South Atlantic). Dis. Aquat. Org. Aug. 45:159–169.
3. Muirhead, S.J. and R.W. Furness. 1988. Heavy metal concentrations in the tissues of seabirds from Gough Island. Mar. Poll. Bull. 19:278–283.