Practical Management of Iron Overload Disorder (IOD) in Black Rhinoceros (BR; Diceros bicornis)

Abstract

Critically endangered black rhinoceros (BR) under human care are predisposed to non-hemochromatosis Iron Overload Disorder (IOD). Over the last 30 years, BR have been documented with diseases that have either been induced by or exacerbated by IOD, prompting significant efforts to investigate and address this disorder. IOD is a multi-factorial chronic disease process requiring an evidence-based and integrative long-term approach. While research continues to elucidate the complexities of iron absorption, metabolism, and dysregulation in this species, preventive treatments are recommended and explained herein. The aim of this report is to highlight the accumulated evidence in nutrition, clinical medicine, and behavioral husbandry supporting the successful management of this disorder to ensure optimal animal health, welfare, and longevity for a sustainable black rhinoceros population.

Keywords: chelation; ferritin; hemochromatosis; hemosiderosis; oxidative stress; phlebotomy; transferrin saturation.

Figure 1

Regulation of iron homeostasis in humans (adapted and simplified from Knutson and Wessling-Resnick 2003) [10]. Dietary iron is absorbed in the duodenum, part of the small intestine. After regulated passage into the body, iron is transported primarily on transferrin (TF) to the bone marrow for red blood cell production. As red blood cells are broken down by phagocytic macrophages where iron is contained in ferritin (black circles), iron is primarily recycled to the bone marrow. Excess iron is stored in the liver, mainly within ferritin protein, until needed. Hepcidin, the iron regulating peptide hormone produced by the liver, blocks entry of iron from the small intestine and release of iron from macrophages by signaling the internalization of transport protein ferroportin. Once iron has entered the body, there is no route of excretion except forms of blood loss.

Figure 2

Decision Tree for approaching iron overload disorder (IOD) assessment in Black rhinoceros (BR) under human care. Serum ferritin in wild BR are from Miller et al. 2016 [47].

Figure 3

Transferrin Saturation (%) across time of two male black rhinoceros (BR1, BR2) at Disney’s Animal Kingdom^®. * Major diet change occurred on 11 October 2009 for both animals. ^a Phlebotomy began on BR1—March 4, 2012; ^b Phlebotomy began on BR2—20 May 2016.

Figure 4

Serum ferritin (ng/mL) across time of two male black rhinoceros (BR1, BR2) at Disney’s Animal Kingdom^®. * Major diet change occurred on 11 October 2009 for both animals. ^a Phlebotomy began on BR1—4 March 2012; ^b Phlebotomy began on BR2—20 May 2016.

Figure 5

Phlebotomy Sites/Venous Access. Options for venipuncture sites with larger vessels that tolerate a large volume for blood collection include the metacarpal vein; (a) lower distal hindlimb or the radial vein; (b) medial forelimb crossing the carpus. Photos were taken in an off-exhibit animal holding area.

Figure 6

Catheterization of the Radial Vein ((a): zoomed out; (b): zoomed in). An 18 gauge catheter placed in the right front radial vein; medial forelimb. Anchoring of the catheter is not necessary, and venous access remains patent without securing. Large bore tubing aids in rapid blood flow into the negative-pressure collection containers. Photos were taken in an off-exhibit animal holding area.

Figure 7

Medical Supplies for Large Volume Blood Collection. Various supply options are available from multiple medical distributors. (1) MILA 80” large animal disposable blood collection set with drip chamber (MILA International, Inc., Florence, KY, USA). (2) Braun 1000 mL empty glass evacuated container (B. Braun Medical, Inc., Bethlehem, PA, USA). (3) Evolution™ UreSil^® pre-vac plastic wound drainage bottle (Pacific Hospital Supply Co., Ltd., Miaoli, Taiwan). (4) JorVet™ 30” large bore IV extension set (Jorgensen Laboratories, Inc., Loveland, CO, USA). (5) Double male Luer lock adapter (Smiths Medical, Dublin, OH, USA).

Figure 8

Protected Contact Voluntary Phlebotomy. Proactive behavioral training through operant conditioning for VTLVP has proven successful and reliable (a) in chute systems and (b) open barn stalls via protected contact. Preference for which training environment is based on individual rhinoceros and the comfort of the animal care staff. Photos were taken in an off-exhibit animal holding area.

Figure 8

Protected Contact Voluntary Phlebotomy. Proactive behavioral training through operant conditioning for VTLVP has proven successful and reliable (a) in chute systems and (b) open barn stalls via protected contact. Preference for which training environment is based on individual rhinoceros and the comfort of the animal care staff. Photos were taken in an off-exhibit animal holding area.

Figure 9

Positive Reinforcement. Reinforcing the rhinoceros to remain calm and still for approximately twenty-five minutes is essential to achieve the desired blood volume. The trainer provides nutritionist-approved dietary items, and tactile attention throughout the session, ensuring the rhino maintains position and is relaxed during the VTLVP process. Photos were taken in an off-exhibit animal holding area.

Figure 10

Post-phlebotomy Reinforcement. An adult male BR building a positively reinforced relationship with a certified veterinary technician after a successful VTLVP session. Reinforcing the individual with their preferred diet items helps establish a trusting relationship and promotes future success. Pictured in the foreground are two full containers (1 L each) of blood obtained for quarterly goals. Photo was taken in an off-exhibit animal holding area.

Figure 11

Highlights of important points and common misconceptions related to iron balance and BR management.