Browse diversity and iron loading in captive sumatran rhinoceroses (Dicerorhinus sumatrensis): a comparison of sanctuary and zoological populations

SERUM FERRITIN CONCENTRATION IS NOT A RELIABLE BIOMARKER OF IRON OVERLOAD DISORDER PROGRESSION OR HEMOCHROMATOSIS IN THE SUMATRAN RHINOCEROS (DICERORHINUS SUMATRENSIS)

The aim of this study was to determine if ferritin is a reliable biomarker of iron overload disorder (IOD) progression and hemochromatosis in the Sumatran rhinoceros (Dicerorhinus sumatrensis) by developing a species-specific ferritin assay and testing historically banked samples collected from rhinos that did and did not die of hemochromatosis. Ferritin extracted from Sumatran rhino liver tissue was used to generate antibodies for the Enzyme Immunoassay. Historically banked Sumatran rhino serum samples (n = 298) obtained from six rhinos in US zoos (n = 290); five rhinos at the Sumatran Rhino Conservation Centre in Sungai Dusun, Malaysia (n = 5); and two rhinos in Sabah, Malaysia (n = 3) were analyzed for ferritin concentrations. Across all US zoo samples, serum ferritin concentrations ranged from 348 to 7,071 ng/ml, with individual means ranging from 1,267 (n = 25) to 2,604 ng/ml (n = 36). The ferritin profiles were dynamic, and all rhinos exhibited spikes in ferritin above baseline during the sampling period. The rhino with the highest mean ferritin concentration did not die of hemochromatosis and exhibited only mild hemosiderosis postmortem. A reproductive female exhibited decreases and increases in serum ferritin concurrent with pregnant and nonpregnant states, respectively. Mean (±SD) serum ferritin concentration for Sumatran rhinos in Malaysia was high (4,904 ± 4,828 ng/ml) compared to that for US zoo rhinos (1,835 ± 495 ng/ml). However, those in Sabah had lower ferritin concentrations (1,025 ± 52.7 ng/ml) compared to those in Sungai Dusun (6,456 ± 4,941 ng/ml). In conclusion, Sumatran rhino serum ferritin concentrations are dynamic, and increases often are not associated with illness or hemochromatosis. Neither a specific pattern nor the individual's overall mean ferritin concentration can be used to accurately assess IOD progression or diagnose hemochromatosis in this rhino species.

Feasibility Study of NMR Based Serum Metabolomic Profiling to Animal Health Monitoring: A Case Study on Iron Storage Disease in Captive Sumatran Rhinoceros (Dicerorhinus sumatrensis)

A variety of wildlife species maintained in captivity are susceptible to iron storage disease (ISD), or hemochromatosis, a disease resulting from the deposition of excess iron into insoluble iron clusters in soft tissue. Sumatran rhinoceros (Dicerorhinus sumatrensis) is one of the rhinoceros species that has evolutionarily adapted to a low-iron diet and is susceptible to iron overload. Hemosiderosis is reported at necropsy in many African black and Sumatran rhinoceroses but only a small number of animals reportedly die from hemochromatosis. The underlying cause and reasons for differences in susceptibility to hemochromatosis within the taxon remains unclear. Although serum ferritin concentrations have been useful in monitoring the progression of ISD in many species, there is some question regarding their value in diagnosing hemochromatosis in the Sumatran rhino. To investigate the metabolic changes during the development of hemochromatosis and possibly increase our understanding of its progression and individual susceptibility differences, the serum metabolome from a Sumatran rhinoceros was investigated by nuclear magnetic resonance (NMR)-based metabolomics. The study involved samples from female rhinoceros at the Cincinnati Zoo (n = 3), including two animals that died from liver failure caused by ISD, and the Sungai Dusun Rhinoceros Conservation Centre in Peninsular Malaysia (n = 4). Principal component analysis was performed to visually and statistically compare the metabolic profiles of the healthy animals. The results indicated that significant differences were present between the animals at the zoo and the animals in the conservation center. A comparison of the 43 serum metabolomes of three zoo rhinoceros showed two distinct groupings, healthy (n = 30) and unhealthy (n = 13). A total of eighteen altered metabolites were identified in healthy versus unhealthy samples. Results strongly suggest that NMR-based metabolomics is a valuable tool for animal health monitoring and may provide insight into the progression of this and other insidious diseases.

Review of laboratory and necropsy evidence for iron storage disease acquired by browser rhinoceroses

Necropsies of two browser rhinoceroses, African black (Diceros bicornis) and Sumatran (Dicerorhinus sumatrensis), often reveal extensive iron-pigment deposition in various tissues. This condition (hemosiderosis) has not been observed in species that are natural grazers, African white (Ceratotherium simum) and Asian greater one-horned (Indian; Rhinoceros unicornis), nor in any species free ranging in the wild. The causes, clinical significance, and consequences of captivity-acquired hemosiderosis have remained controversial despite two decades of compelling evidence that iron tends to accumulate logarithmically in all members of affected species in proportion to periods of expatriation; total-body iron loads can reach 10-fold in less than 3 yr and eventually exceed reference ranges by two to three orders of magnitude; iron overburdens are accompanied by laboratory and histopathologic evidence of cellular injury, necrosis and other clinical consequences characteristic of chronic pathologic iron storage [corrected] disorders (ISD) in humans and other species (hemochromatosis); and that ISD develops in many other exotic wildlife species displaced from their natural habitats. The historical evolution of evidence establishing the development of pathologic ISD in browser (but not in grazer) rhinoceroses and the possible relevance of ISD to other conditions affecting these two species will be reviewed. Evidence reviewed includes new as well as published data derived from quantitative measurements of iron analytes in sera and necropsy tissues and histopathologic evaluations of current and past necropsies of captive and free-ranging rhinoceroses of all four available species. The evolutionary, husbandry, and conservation implications of ISD in rhinoceroses are relevant to understanding ISD acquired by many other species of exotic wildlife when displaced from their natural environments.