Chronic Kidney Disease in Non-Domestic Felids in Australian Zoos

Abstract

Chronic kidney disease (CKD) is a significant cause of mortality in non-domestic felids in Australian zoos with a prevalence of 7.1% overall, and 31% amongst adult felids. A high prevalence of CKD was demonstrated in adult Bengal tigers (Panthera tigris tigris, 55%), Sumatran tigers (Panthera tigris sumatrae, 75%) and fishing cats (Prionailurus viverrinus, 38%). Examination of all accessible clinical records of 1,015 felids from ten Australian zoos in a 50-year period (1965–2015) demonstrated that lethargy and inappetence were the predominant clinical signs, with polydipsia but not polyuria commonly reported, followed by weight loss, ataxia and dehydration. The serum biochemical derangements of azotaemia, hyperphosphataemia, hypercholesterolaemia, hypokalaemia, and hypochloraemic metabolic acidosis were seen, although felids rarely became anaemic. The longitudinal changes observed in serum creatinine and urea concentrations and urine specific gravity (USG) demonstrate that CKD is a covert and insidious disease, with onset of inadequately concentrated urine (i.e. lowered USG) being the earliest, specific diagnostic marker, as clinically normal non-domestic felids concentrate their urine to a very high degree. Voided urine was shown to be an extremely useful sample, exquisitely suited to the zoo context, being cost effective to test, requiring no human-felid contact to collect, and abundantly available due to the reliable urination habits of most zoo felids. Urinary tract infections could be identified and distinguished from background environmental contamination by visual inspection of voided urine samples. While age and species were identified as the most significant risk factors for CKD, some aetiologies of CKD in non-domestic felids are associated with treatable conditions, such as infections of the genitourinary tract and pyometra in females, informing veterinary care and husbandry decisions in management of non-domestic felids in Australian zoos.