Aggressive Behavior in a Moluccan Cockatoo (Cacatua moluccensis) with Zinc Toxicosis

Heather E. McClure and Cheryl B. Greenacre

Department of Small Animal Medicine, College of Veterinary Medicine, University of Georgia, Athens, GA 30602 USA

Abstract. A hand-raised Moluccan Cockatoo (Cacatua moluccensis) presented to the University of Georgia College of Veterinary Medicine with a gradual onset of aggression over an 18-month period. No significant abnormalities were detected upon physical examination. Diagnostic abnormalities included a stress leukogram and a serum zinc concentration of 6.5 parts per million (ppm; reference interval = < 2.0 ppm). The aggressive behavior was characterized by flightiness. If approached by any individual, especially while caged, the cockatoo would raise its crest, flap its wings, vocalize, and attempt to bite. Following initial chelation therapy with Edetate Calcium Disodium (Calcium EDTA) and behavioral modification sessions, the cockatoo became slightly easier to handle and less flighty. This case emphasizes the importance of extensive diagnostic testing when evaluating aberrant behavior in avian patients.

Key Words: Aggression, Behavioral changes Cacatua moluccensis, Moluccan cockatoo, Zinc toxicosis

Introduction

In birds, just as in many other companion species, changes in behavior can be caused by a myriad of etiologies. These etiologies include, but are not limited to, metabolic, biochemical or hormonal imbalances, primary neurologic disorders, toxicoses, and environmental stressors.

Lead and zinc toxicoses are common in psittacines. ¹ While zinc toxicosis is diagnosed less frequently than lead toxicosis, many of the clinical signs are similar in avian patients. Common pansystemic clinical signs include lethargy, depression, anorexia, anemia, regurgitation, polyuria, polydipsia, diarrhea, emaciation, and decreased fertility. ^1-3 Neurologic signs may include ataxia, head tilt, blindness, circling, paresis, paralysis and convulsions. Some birds may show no clinical signs aside from weakness, altered behavior, or chronic weight loss.

Common sources of zinc include galvanized wire, containers and dishes, United States pennies minted after 1982, hardware cloth, Monopoly® game pieces, rubber stoppers in some glass blood sample tubes, and some paints and fertilizers. ^1-3 Zinc is absorbed via the gastrointestinal tract of birds. It is then distributed to various tissues and organs including the liver, kidneys, pancreas, gastrointestinal tract, reproductive organs, and plasma. ^1,3 The pancreas is the primary target organ, resulting in pancreatic cell necrosis secondary to interference with cellular protein synthesis.

Tests used to diagnose zinc toxicosis include history of metal exposure, clinical signs, radiographs, and serum or tissue zinc concentrations. A serum concentration greater than 200 mcg/dl (2.0 ppm) is considered elevated. Caution must be used when blood is drawn and submitted for serum zinc levels as the rubber stopper of some specimen tubes contains zinc and may falsely elevate the test values. Chelation therapy for zinc toxicosis may include one or more of the following agents: Calcium EDTA, d-penicillamine, and 2,3-dimercaptosuccinic acid (DMSA). Various bulking and lubricating agents may be administered in addition to chelating agents. ^1-3 In cases where one or more metal fragments are visible radiographically, endoscopic removal of the fragments or proventricular flushing may be indicated.

Case Report

A 4-year-old, male, hand-raised Moluccan Cockatoo (Cacatua moluccensis) was presented for evaluation following gradual behavioral changes occurring over an18-month period. The owner acquired the cockatoo at 10 months of age. For approximately the first 18 months following its purchase, the bird was friendly, interactive, and easy to handle; however, at 2 years of age the bird began to exhibit subtle changes in behavior. He became more timid, especially when caged, and was less interactive towards strangers and the owner. This tendency towards timidity progressed to pronounced fear and flightiness and finally to periods of aggression when approached.

The bird was housed indoors during winter months and in a screened-in-porch during the spring and summer. The painted cage had originated from Mexico. The bird was caged alone; however, 10 other pet psittacines of varying species were kept in the house. No breeder pairs or female Moluccan Cockatoos were present. The bird's diet consisted of a mixture of commercially-available, artificially colored and naturally colored pellets supplemented with fresh vegetables and fruits. The owner had noted no other abnormalities aside from the aggressive behavior. No major changes had occurred in the bird's environment within the last year.

Clinical abnormalities were not observed on physical examination. The differential diagnosis included behavioral changes associated with sexual maturation, physiologic or metabolic disorder, heavy metal toxicosis, and environmental stressors. The initial laboratory testing included a complete blood count (Table 1), biochemical analysis (Table 2), radiographs (Figs. 1 & 2), fecal flotation, fecal saline smear, fecal Gram stain cytology, whole blood lead concentration, and serum zinc concentration. All tests were within normal limits with the exception of a mild stress leukogram (leukocytosis, lymphopenia, and monocytosis), and an elevated serum zinc concentration of 6.5 ppm (reference interval = < 2.0 ppm; Table 3).

Fig. 1. Moluccan Cockatoo, radiograph, lateral view. Metal densities are not present.	Fig. 2. Moluccan Cockatoo, radiograph, ventrodorsal view. Metal densities are not present.

Prior to determining serum zinc levels, the primary diagnosis for the aggressive behavior was reproductive frustration, and the patient was treated with a series of human chorionic gonadotropin (HCG) ^a at a dosage of 1000 IU/kg IM on days 1,3 and 7. ⁴ The owner was also instructed to begin behavioral modification sessions with the bird. During these sessions, the bird would be taught to respond to specific commands (i.e. , "step up," "stay," and "step down") thereby re-establishing the owner as the dominant individual in the relationship.

After the result of the serum zinc analysis was received, the patient was immediately placed on chelation therapy with Calcium EDTA ^b at a dosage of 35mg/kg IM BID for 5 days, and lactulose ^c at a dosage of 0.5ml/kg PO every 12 hours for 14 days. ⁴ The bird was placed in a new commercially-available enclosure with new stainless steel food dishes as well.

One month following initial presentation, the owner reported that the bird was slightly less aggressive when approached. While the owner was still unable to easily handle the bird, she was beginning to re-establish herself as the dominant individual in the relationship.

During the recheck physical examination, abnormalities were not detected except that the bird remained extremely aggressive and difficult to manage. Results of a second serum zinc analysis showed a mild elevation of 2.4 ppm. Chelation therapy (Calcium EDTA, 35mg/kg IM BID for 5 days) was repeated. The owner declined repeat determinations of serum zinc concentration at this time. The owner reported having very limited time to implement behavioral modification sessions with the bird; however, the bird still appeared to have improved following chelation therapy in that he was more interactive with people, more talkative, and slightly less flighty.

Discussion

The most likely source for zinc in this patient was the older painted iron cage and ceramic food bowls, all of which originated in Mexico. Chemical analyses of the paint and glaze would be necessary to confirm that the cage and/or food bowls were the sources of zinc. Metal fragments were not identified radiographically in this cockatoo; however, heavy metal toxicosis may be present without radiographic evidence of metallic particles. In this case, the diagnosis of zinc toxicosis was based solely upon serum zinc concentrations; the diagnosis would not have been made upon radiographic evaluation alone. This case serves to illustrate the necessity of a thorough clinical evaluation of every avian patient.

This patient may also be suffering from a primary behavioral problem. Treatment with one or more behavior-modifying pharmaceuticals and/or training may be necessary to completely correct the aggressive behavior. The response to chelation therapy suggests, but does not prove, an association between the zinc toxicosis and behavioral changes. Further studies and continued evaluation of this case must be performed in order to confirm an association between serum zinc concentrations and aggressive behavior. Serum estradiol and testosterone concentrations were not performed in this case.

Many veterinarians are pressured by clients to prescribe behavior-altering pharmaceuticals in an effort to alleviate aggressive and/or destructive behaviors in their companion birds. In some cases, such medications are justified; however, in many cases, such medications do not treat the underlying problem but simply mask the clinical signs.

Sources and Manufacturers

^a Follutein, Solvay Animal Health, Inc. , Mendota Heights, MN, USA ^b Calcium Disodium Versonate, 3M Riker, Northridge, CA, USA ^c Chronulac, Marion Merrell Dow, Kansas City, MO, USA

References

1. Dumonceaux G, Harrison GJ: Toxins. In:Ritchie BW, Harrison GJ, Harrison LR (eds). Avian Medicine: Principles and Application. Wingers Publishing Inc. , Lake Worth, Florida, 1994, pp. 1030-1052.

2. Labonde J: Household Poisoning in Caged Birds. In: Kirk RW (ed). Kirk's Current Veterinary Therapy XII, Small Animal Practice. W B Saunders Co. , Philadelphia, Pennsylvania, 1995, pp. 1299-1303.

3. Romagnano A, Grindem CB, Degeneres L, Mautino M: Treatment of a hyacinth macaw with zinc toxicity. J Avian Vet Med Surg 9:185-189, 1995.

4. Johnson-Delaney CA: Bird Section. In: Johnson-Delaney CA, Harrison LB (eds). Exotic Companion Medicine Handbook for Veterinarians. Wingers Publishing Inc. , Lake Worth, Florida, 1996, pp. 1-38.

5. Louisiana Veterinary Medical Diagnostic Laboratory, P.O. Box 25070, Baton Rouge, LA 70894

This Page Last Updated May 15, 1998

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