A RETROSPECTIVE STUDY OF END-STAGE RENAL DISEASE IN CAPTIVE POLAR BEARS (URSUS MARITIMUS)

Abstract

This retrospective study summarizes 11 cases of end-stage renal disease (ESRD) in captive polar bears (Ursus maritimus) from eight zoologic institutions across the United States and Canada. Ten bears were female, one was male, and the mean age at the time of death was 24 yr old. The most common clinical signs were lethargy, inappetence, and polyuria-polydipsia. Biochemical findings included azotemia, anemia, hyperphosphatemia, and isosthenuria. Histologic examination commonly showed glomerulonephropathies and interstitial fibrosis. Based on submissions to a private diagnostic institution over a 16-yr period, ESRD was the most commonly diagnosed cause of death or euthanasia in captive polar bears in the United States, with an estimated prevalence of over 20%. Further research is needed to discern the etiology of this apparently common disease of captive polar bears.

Energetic and health effects of protein overconsumption constrain dietary adaptation in an apex predator

“…Zoo polar bears dying of kidney disease died 10 years earlier than bears dying of other causes and 5–9 years earlier than the maximum age achieved by wild polar bears. Serum urea, creatinine, and phosphorus levels measured in over 600 wild adult polar bears (this study) and among 35 wild polar bears in Svalbard 47 were consistently well below levels documented in zoo polar bears with chronic kidney disease 27 , suggesting that kidney disease is not an affliction in wild polar bears. Thus, the potential that high protein intake may affect metabolism and kidney and liver health suggests the need for careful consideration of protein levels in formulated diets for carnivores (i.e., species in the order carnivora)—particularly ursids which have a long evolutionary history of omnivory and diets dominated by carbohydrates or fat.…”

“…Serum urea (15.7 ± 12.2 mg/dl; range = 1–85.5; n = 628) and creatinine (1.1 ± 0.4 mg/dl; range = 0.3–3.5; n = 628) levels of wild adult polar bears sampled in the southern Beaufort and Chukchi Sea subpopulations were well below values observed in zoo polar bears with chronic kidney disease (serum urea: 180.1 ± 77.8 mg/dl; n = 9; creatinine: 14.8 ± 12.7 mg/dl; n = 90) 27 . Mean phosphorus levels of wild adult bears (5.6 ± 1.3 mg/dl; n = 628) were also below those of polar bears with kidney disease (14.5 ± 6.9 mg/dl; n = 8) 27 , but 3 wild bears exhibited phosphorus levels above 10.0 (range 1.7–13.2 mg/dl). For wild polar bears age 20 and older (n = 32), urea averaged 13.8 ± 11.8 (range 3–40), creatinine averaged 1.1 ± 0.3 (0.7–2.0), and phosphorus averaged 5.7 ± 1.9 (range 2.9–13.2).…”

“…Because zoo polar bears are also fed carbohydrates which have lower calorie density than fats, protein contributes approximately twice as much to their caloric intake (37%) when compared to diets consumed by wild bears (18%) and selected by zoo bears in ad libitum trials (24%). Chronic kidney disease (29% of zoo polar bear mortalities from 1995 to 2011 27 ; 37% this study) and liver disease and cancers (32%) are the primary causes of death in zoo polar bears, the former of which may have increased in prevalence in recent years (this study). Zoo polar bears dying of kidney disease died 10 years earlier than bears dying of other causes and 5–9 years earlier than the maximum age achieved by wild polar bears.…”

“…Blood samples were collected from 628 adult (age 5 + years) polar bears of both sexes captured in two polar bear subpopulations that range in Alaska (the Chukchi and southern Beaufort Sea subpopulations) from 2004 to 2017 and analyzed for serum urea, creatinine, and phosphorus levels to determine if levels were consistent with those of zoo polar bears exhibiting chronic kidney disease reported by Ref. 27 : serum urea (180.1 ± 77.8 mg/dl; n = 9), creatinine (14.8 ± 12.7 mg/dl; n = 9) and phosphorus levels (14.5 ± 6.9 mg/dl; n = 8). All wild bears were sampled between March and May.…”

The Oral and Skin Microbiomes of Captive Komodo Dragons Are Significantly Shared with Their Habitat

“…The decreased exposure to the outdoors and other microbe-rich locations together with the increased indoor lifestyles (working and living) and obsessive cleaning habits that characterize Western culture today have led to the formulation of the hygiene hypothesis ( 27 ), which posits that a lack of exposure to beneficial microbes present in the environment leads to the increase in disease that we have seen in the past century. Captive animals, which live in enclosed environments not equivalent to their normal environments in the wild, experience diseases that are associated with or worsened by the captive environment, including gastric ulcers (vervet monkeys [ 28 ]), intestinal stricture (green sea turtles [ 29 ]), and end-stage renal disease (polar bears [ 30 ]). As we and others have shown, human houses and Komodo dragon zoo enclosures represent closed locations characterized by possibly circular microbial sharing with less microbial input from outside environments than that received by animals and humans living and working predominantly outdoors.…”