ISRAEL JOURNAL OF
VETERINARY MEDICINE
HEAVY METAL TOXICITY IN PSITTACINE BIRDS
Aizenberg I.1 Miara L.2 and Ulman O.2
1. Hebrew University of Jerusalem, School of Veterinary Medicine
2. 'Kol-Hay' Veterinary Clinic, Rehovot
Summary
Heavy metal toxicities are of major concern in wild and captive
avian species. In wild birds it is impossible to fully control
heavy metal toxicity, nevertheless it is our responsibility to
prevent it in captive species. Of the heavy metals, lead and zinc
are the most important in captive birds since they are common
in their immediate environment. Clinical signs of lead and zinc
toxicity (LZT) are very similar but are not specific since many
disease conditions can show the same signs. Therefore a
thorough history should be taken followed by a physical
examination, radiographs, blood tests and blood and plasma
levels of lead and zinc. Specific treatment is indicated with a
good prognosis according to the severity of the poisoning.
A case of zinc toxicity in a pair of Cacatua Alba (White
Cockatoo) will be discussed.
Introduction
Metal toxicosis is a major problem affecting both wild and captive avian
populations (1,2,3,4). Historically, toxicities involving lead, zinc, iron, or copper
appear to have the greatest clinical impact on birds. For example, lead and zinc
toxicities are commonly recognized causes of illness in pet psittacine birds, birds
in zoological collections, and waterfowl (2,5,6,7). Lead toxicosis due to ingestion
of lead shot is claimed to be the cause of death of more than 1.6—2.4 million
ducks annually. (8)
Parrots are known as very curious and active creatures who like to chew anything
in their environment. Since there are many objects in their immediate
environment which contain zinc and almost as many that contain lead they are
prone to LZT. (5,6)
Objects that contain zinc are galvanized cages, food and water dishes, toys,
jewelry, chains etc. Objects that contain lead include batteries, curtain weights,
PVC, toys etc. Clinical signs of LZT are regurgitation, diarrhea, anorexia
polydipsia and polyuria, dyspnea, depression, weakness, ataxia, seizures, weight
loss and death. (9) The final diagnosis is made by measuring the levels of lead
and zinc in the blood. Normal blood lead levels are considered to be less than
0.2ppm, and normal plasma zinc levels are less than 2ppm. (9) Radiography is a
useful method for imaging metallic objects in the gastrointestinal tract.
Endoscopy can aid in finding metallic objects in the ventriculus as well as for
extracting them. Complete blood count (CBC) may show heterocytosis, and
anemia. Blood chemistry can show dehydration and elevated uric-acid levels.
Treatment includes supportive care, the use of specific chelating agents and
bulking and cathartics. Chelating agents used are Ca-EDTA (calcium disodium
ethylene diamine tetraacetic acid), DMSA (Dimercaptosuccinic acid) and DPenicillamine. (9)
Case report:
A pair of 2.5 year old white cockatoos was presented with clinical signs of
depression, regurgitation, diarrhea, dyspnea and weakness. The male was more
affected than the female. Both were housed in a galvanized mesh cage locked by
a galvanized lock. Radiographs revealed small metallic objects in both parrots.
The only abnormality in the blood tests was mildly elevated uric acid (11.3mg/dl,
normal: 3.5-9.3).
Fecal examination did not reveal any pathological finding. Chlamidial IFA was
negative. Plasma zinc level of the male was above 3ppm (there was not enough
plasma from the female to meet the laboratory requirement). A final diagnosis of
zinc toxicity was made. Initial treatment included parenteral fluids (lactated
Ringer), oral D-penicillamine (25 mg bid for 5 days), and intramuscular CaEDTA (35 mg bid for 5 days). The birds also got psyllium and metoclopramid
(Pramin) before each meal. Both cockatoos showed a marked improvement after
2 days. No radiograph follow-up or plasma zinc levels were done since the
parrots were fully recovered according to the owner.
Discussion
Heavy metal toxicities are more common than it seems. Since the environment of
the captive birds is full of material made from zinc and lead we must investigate
for LZT in addition to other diseases. (2,3,5,6) Clinical signs of LZT are not
pathognomonic but are common to many other conditions, therefore LZT should
always be a differential diagnosis. A thorough history is probably the most
important step in the diagnosis. Radiography, plasma zinc levels and blood lead
levels can lead to a final diagnosis. CBC and blood chemistry might support the
diagnosis. A correct diagnosis will lead to the appropriate treatment and will
improve the prognosis. Misdiagnosis will probably lead to the death of the bird.
An important part of the treatment is the prevention of reoccurring toxicities.
Owners should be advised about the risk of hazardous materials in the birds'
environment.
References:
1. Zook BC, Sauer RM, Garner FM. Lead poisoning in captive wild animals.
Wildl. Dis. 8:264-272, 1972.
2. Woerpel R.W, Rosskopf WJ. Heavy-metal intoxication in caged birds-part I.
Compend. Cont. Educ. Pract. Vet. 4:729-736, 1982.
3. Smith A. Zinc toxicosis in a flock of Hispaniolan Amazons.
Proc. Ann. Conf. Assoc. Avian Vet. 447-453, 1995.
4. Beyer N.W., Spann J.W.,†Sileo L. and Franson J.C. Lead poisoning in six
captive avian species. Archives of Environmental Contamination and Toxicology
17:121-130, 1988.
5. Howard B.R. Health risks of housing small psittacines in galvanized wire
mesh cages. J. Am. Vet. Med. Assoc. 200:1667-1674, 1992.
6. Doneley R. Zinc toxicity in caged and aviary birds-‘‘new wire disease.’’ Aust.
Vet. Pract. 22:6-11, 1992.
7. Van Sant F. Zinc and parrots: more than you ever wanted to know. Proc. Ann.
Conf. Assoc. Avian Vet. 305—313, 1998.
8. Osofsky A. et al. Determination of Normal Blood Concentrations of Lead,
Zinc, Copper, and Iron in Hispaniolan Amazon Parrots (Amazona ventralis).
Journal of Avian Medicine and Surgery 15:31—36, 2001.
9. Bauck L, and LaBonde J. Toxic diseases. In: Altman RB, Clubb SL,
Dorrenstein GM, Quesenberry K, eds. Avian Medicine and Surgery.Philadelphia,
PA: WB Saunders; 604—613, 1997.