Morphologic Evidence of Hypertension in Western Gray Kangaroos (Macropus fuliginosus)
American Association of Zoo Veterinarians Conference 2007
Rebecca Kagan1, DVM; Kayleen Gloor2,3, DVM; Natalie D. Mylniczenko4, DVM, MS; Jennifer N. Langan4, DVM, DACZM; Michael Kinsel1, DVM, DACVP; Karen A. Terio1, DVM, PhD, DACVP
1University of Illinois Zoological Pathology Program, Loyola University Medical Center, Loyola University, Maywood, IL, USA; 2Virginia-Maryland Regional College of Veterinary Medicine, Virginia Tech, Blacksburg, VA, USA; 3VCA Veterinary Referral Associates, Gaithersburg, MD, USA; 4Brookfield Zoo, Brookfield, IL, USA
Marked renal vascular changes, suggestive of hypertension, were noted among several adult Western gray kangaroos (Macropus fuliginosus) some of which had clinical nervous system deficits, including blindness. To determine vascular lesion prevalence and other changes suggestive of hypertension, case histories and archival tissue sections from 20 adult (8.12) kangaroos that died or were euthanatized between 1994 and 2006 were reviewed. Average age at death was 9.7 y. Antemortem blood work was unremarkable in all cases. Fourteen (70%) kangaroos had morphologic evidence of hypertension. Lesions included varying degrees of juxtaglomerular hyperplasia and tortuous renal arterioles with increased thickness of the tunica media and variable amounts of smooth muscle hypertrophy and/or hyperplasia. Occasional arteriolar reduplication also was evident. Similar vascular reduplication was noted in the CNS of one animal with neurologic signs. Four kangaroos had histologic evidence of antemortem retinal detachment, a common sequel of hypertension.
Hypertension (persistently high blood pressure) can be essential (idiopathic) or secondary to renal disease, endocrine disorders, diet and/or stress. In animals, hypertension can be difficult to assess as blood pressure evaluation and parameters can be altered by stress of capture and anesthesia. The cause of presumed hypertension in this mob is uncertain. Significant underlying renal disease was not noted in affected animals and only 3 animals had thyroid abnormalities. The majority of affected animals were females or low-ranking males; therefore, social stressors may play a role in pathogenesis. Other potential predisposing factors, including genetics and diet, are being evaluated.
We would like to acknowledge Jane Chladny and the University of Illinois Veterinary Diagnostic Laboratory’s histology laboratory for slide preparation and Zoological Pathology Program faculty, residents, and students who assisted with the necropsies included in this study. We would also like to thank Brookfield Zoo hospital staff for their essential support, and Mark Warneke for aid in compiling case materials.