Gerda R. Bruins-van Sonsbeek, DVM
Iron storage disease (ISD) is a pathological complication that is seen in some captive animal species.3 ISD has been identiﬁed in browsing rhinoceros species (black rhino, Diceros bicornis, Sumatran rhino, Dicerorhinus sumatrensis), whereas grazing rhino species (white rhino, Ceratothenum simun, greater one-horned rhino, Rhinocerus unicornis) appear less susceptible.1,6,7 Long-term ISD damages various organs, in particular liver and bone marrow,7 and can cause fertility problems via damage to the testis in male rhinos, and irregular oestrous cycle in female rhinos [pers. communication Marcus Clauss].
Iron storage disease is characterized by accumulation of iron in the body tissues, and can be diagnosed in humans by assessing the serum ferritin levels. This is a species-specific protein, and there is no validated assay for rhinos at this time. ISD in rhinos is potentially currently suspected and monitored by measuring serum iron and total serum iron binding capacity, and calculating transferrin saturation (%TS) from these values. Feeding susceptible species a low-iron diet is a commonly adapted approach in captivity. Additionally, because the iron is not excreted once in the body except via bleeding4 or production of young, treatment of, and preventative measures against, ISD consist of regular phlebotomy and, in females, regular breeding.5
A management and treatment protocol was made based on experience at Rotterdam Zoo, which included monitoring of %TS, hematology and chemistry with special attention to GGT, and controlling iron uptake by analyzing the different food items and excluding items containing high iron levels, with a maximum daily total iron intake under 3000 mg, lower than the recommended maximum intake of 6000 mg.2 At high %TS, large volume phlebotomies were performed. However, evidence that using %TS for ISD monitoring still needs to be provided. Iron concentration in the food (n=3 animals) did not correlate to %TS. Regular phlebotomies in 1 animal reduced %TS from 99% to below 80%, over 5 months and below 60% within one year with a subsequent increase to 80% over a 1 year time period when phlebotomies were ceased.
The author would like to thank the rhino keepers and the head of the African section of Rotterdam Zoo for their support and commitment to the animal training program, and Marcus Clauss for comments.
1. Beutler E, West C, Speir JA, Wilson IA, Worley M. The hHFE gene of browsing and grazing rhinoceroses: a possible site of adaptation to a low-iron diet. Blood Cells Mol Dis. 2001;27:342–350.
2. Clauss M, Dierenfeld E, Giff J, Klasing K, Kouton L, Lavin S, Livingston S, Nielson B, Schlegel M, Sullivan K, Valdes E, Ward A. IOD in rhinos – nutrition group report: report from the nutrition working group of the international workshop on iron overload disorder in browsing rhinoceros. J Zoo Wildl Med. 2012;43:108–113.
3. Cork SC. Iron storage disease in birds. Avian Pathol. 2000:28:7–12.
4. Cornelissen H, Ducatelle R, Roels S. Successful treatment of a channel-billed toucan (Ramphastos vitellinus) with iron storage disease by chelation therapy: sequential monitoring of the iron content of the liver during the treatment period by quantitative chemical and image analyses. J Avian Med Surg. 1995;9:131–137.
5. Mylniczenko ND, Sullivan KE, Corcoran ME, Fleming GJ, Valdes EV. Management strategies of iron accumulation in a captive population of black rhinoceroses (Diceros bicornis minor). J Zoo Wildl Med. 2012;43:83–91.
6. Paglia DE, Dennis P. Role of chronic iron overload in multiple disorders of captive black rhinoceroses (Diceros bicornis). Proc Am Assoc Zoo Vet. 1999:163–171.
7. Paglia DE. Iron storage syndrome in rhinoceros. Potential role for rhino keepers in prevention and therapy. Proc 4th Intl Rhino Keepers Workshop. 2005:1–10.