Zinc Toxicity in a Hyacinth Macaw
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, B.C.
Copyright © Gillian A.Willis. Permission to re-use any
part of this text (whole or in part) must be obtained from the
author.