Miller, R.E., 1994. Diseases of black rhinoceroses in captivity: pp. 180-185
 | In: Penzhorn, B.L. et al. Proceedings of a symposium on rhinos as game ranch animals. Onderstepoort, Republic of South Africa, 9-10 September 1994: pp. i-iv, 1-242 |
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Captive |
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Diseases |
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Black Rhino |
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Diceros bicornis. HAEMOLYTIC ANAEMIA. Our investigations centred on possible causes for the hemolytic anaemia. A fatal case of haemolysis at the St. Louis Zoo led to subsequent surveys that noted 47 episodes of haemolysis in 39 individual black rhinoceroses. Cases can be classified as 'primary,' i.e., those haemolytic events that occur without other obvious underlying disease, and 'secondary,' those cases that occur as agonal events in rhinoceroses dying of other causes. Although several familial groupings of affected rhinoceroses exist, no sex, age, or captive-bred vs. wild-caught patterns were evident. Early reports suggested that many of the acute cases of haemolysis were associated with leptospirosis. Indeed, with the advent of the fluorescent antibody (FA) test for Leptospira interrogans, many cases that were not evident by titres were positive. At the present time, biannual vaccination of all black rhinoceros with leptospiral bacterins that contain the serovars icterohemorraghiae and grippotyphosa (serovars that have elicited elevated titres in two reports of rhinoceroses surviving haemolysis) has been recommended. (Author's note: Leptospire interrogans has also been identified in the tissues of an aborted greater one-horned Asian rhinoceros (Rhinoceros unicomis) calf at the Bronx Zoo.)
However, not all of the cases of haemolysis could be accounted for by leptospiral infection, and a series of investigations was initiated to determine if other aetiologies or properties inherent in the black rhinoceros red blood cell (RBC) increased their susceptibility to haemolysis from a number of causes (drug exposure, bacterial infection, etc.). Various studies indicated that the anemia was unlikely to result from autoimmune disease, uncomplicated vitamin E deficiency, nor an unstable haemoglobin.
The most significant findings resulted from investigations into the metabolism of the black rhinoceros RBC. Initial studies focused on RBC levels of glucose-6-phosphatase dehydrogenase (G-6 PD) and other enzymes commonly recognized to cause haemolysis in man, but those levels were either normal or elevated compared to human normals . However, on a more fundamental level, the black rhinoceros RBCs were noted to be markedly deficient in energy (ATP), when compared to other mammalian species.
The RBCs of white rhinoceroses, a species which has been apparently healthy in captivity, were also low in ATP, but they also had significantly higher levels of the enzyme catalase than black rhinoceroses. The full significance of this is unknown, but further metabolic studies are underway. Interestingly enough, Dr. Paglia has hypothesized that the energy deficiency of the black rhinoceros RBC could be an adaptive characteristic for haemic parasitism in the same manner than G-6-PD deficiency is considered adaptive in man. Dr. Paglia, is presently on sabbatical in the laboratories of Dr. Eric Harley at the University of Cape Town.
At the present time, suggested treatment of acute cases of haemolysis is supportive and includes penicillin and possibly dihydrostreptomycin (in the event that it is leptospirat-induced), parenteral vitamin E (to assist in the maintenance of membrane stability), enteral andlor parenteral phosphorus supplementation (as many of the chronically haemolytic individuals have become hypophosphataemic)', and possibly blood transfusion. The latter has been attempted in two black rhinoceros as preliminary findings suggest that rhinoceroses do not have inherent antibodies to other blood groups of their species.
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Diseases of black rhinoceroses in captivity
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