The following article is used with the written permission of the author, Gillian Willis, pharmacist and toxicologist.
Case Report: A 3-year-old, hand-raised, male hyacinth macaw was examined by an avian veterinarian because of loose, foul-smelling stools, anorexia, weight loss, lethargy, depression, ataxia and impaired vocalizations of 4 day's duration. It had refused food and water for 24 hours and its clinical condition was deteriorating rapidly.
The bird was housed alone in a cage and lived in the family room with 14 healthy psittacines. Its diet consisted of a variety of nuts, monkey chow, fruits, vegetables and table food.
When healthy, it was in the habit of rocking its cage, running its beak up and down the chrome-plated cage bars and occasionally snapping them off. Over the previous 6 months, it had destroyed three different cage door padlocks.
On examination, the bird was lying down, fluffed, depressed and severely dehydrated. It was thin and had voluminous, foul-smelling, bright lime-green feces with normal urates and urine.
The differential diagnosis included heavy metal poisoning (especially lead or zinc). Samples of blood, feces, and choanal and cloacal smears were taken for laboratory analysis.
The bird was treated initially with lactated Ringer's solution (IV and SC) and antibiotics and was placed in a hospital cage where it was given oxygen. It responded to supportive care and was able to stand and drink within 6 hours, but it remained anorexic. It was tube fed and started on antifungal therapy.
After 20 hours of hospitalization, the bird was stable enough to have x-rays taken. These revealed a metallic object measuring approximately 6 x 2 x 2 mm in the ventriculus.
Laboratory results showed markedly high plasma zinc concentrations (24 ppm). Chelation therapy to bind the zinc and laxatives to hasten the passage of the metallic object were instituted. Surgical removal of the foreign body was contraindicated because of the bird's weakened condition and because the object was small enough to pass.
By the morning of the third day, the bird was eating, drinking and vocalizing. The bird was discharged home with the owners with instructions to continue with chelation therapy, laxatives, antibiotics and an antifungal drug.
When re-examined 12 days after admission, the bird was clinically normal and it had gained weight. An x-ray showed that the metallic object had passed. Plasma zinc had dropped to 1.5 ppm (normal range).
The macaw continued to improve and 40 days after admission, had continued to gain weight (26 % increase). Plasma zinc had dropped to 1.0 ppm.
The potential sources of zinc were the destroyed padlocks and the chrome-plated cage bars. Analysis showed that the padlocks contained zinc, steel, brass and nickel and that the cage bars also contained zinc.
Discussion: Zinc toxicity in birds results in gastroenteritis, necrotizing ventriculitis, as well as damage to the pancreas, kidneys and the liver. Treatment consists of supportive care, chelation therapy and endoscopic or surgical removal of the foreign body. Small foreign bodies may pass with the addition of laxatives to the diet.
Zinc is extremely toxic to birds. Sources include galvanized cage wire, clips or staples, bird toy snaps, zippers, keys, nails, plumbing nuts, quick links, nuts on animal transport cages, hardware cloth, padlocks, some antirust paints, shampoos and skin preparations.
Padlocks are frequently used on bird cages. Other types of locking devices should be considered on cages of large birds who may attempt to chew on the padlock. Chrome- plated cages should be avoided for larger birds.Reference: Romagnano A, Grinden, CB, Degernes, Mautino M. Treatment of a Hyacinth Macaw with Zinc Toxicity. J Avian Medicine and Surgery. 1995;9:185-189.
Gillian Willis
Vancouver, BC