8/14/2019 EXOTC-Lead and zinc toxicosis from a retained projectile in a bird

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Cheryl B. Greenacre, DVM,

Diplomate ABVP (Avian)Branson W. Ritchie, DVM, PhD,

Diplomate ABVP (Avian)University of GeorgiaCollege of Veterinary Medicine

Athens, Georgia

An adult, male lesser sulfur-crested cockatoo (Cacatuasulphurea sulphurea) was pre-

sented to the University of Georgia

College of Veterinary MedicineTeaching Hospital with a history offalling off its perch and an inabilityto grasp with the feet for 15 minutesafter falling. A similar episode mayhave occurred 2 days earlier. Theclient reported that the bird other-

wise had a normal attitude, appetite,and droppings. The bird had beenpurchased at a pet store 4 years earli-er and was housed within an en-closed porch in a 1.5 1 1m,

brass-plated, commercial bird enclo-sure. A polyvinylchloride pipe wasavailable as a perch. Metallic materi-als containing lead or zinc were notobserved within the enclosure, andthe bird did not have unsupervisedaccess to the house. A cockatiel, dog,and cat also resided in the householdand were clinically sta-ble. The bird was fed acommercial parrot-seedmix and had access toa mineral block.

Clinical FindingsOn physical exami-

nation, the bird wasnoted to have an open,import-type band onone leg. The bird was bright and alertbut thin (329 g). An 8 10mm,firm, immobile, dark, subcutaneousmass was present 1 cm caudal to thecrest and dorsal to, but partially in-volving, the frontal bone on the mid-line. Radiographs of the head indicat-ed a pellet-shaped, radiodense foreignbody partially imbedded in thefrontal bone (Figure 1). There was no

Compendium May 1999 20TH ANNIVERSARY Small Animal/Exotics

radiographic evidence that the interiorof the cranium was affected. Whole-body radiographs showed no othermetallic densities, but hepatomegalyand mild proventricular dilation werepresent. The client was unaware ofany circumstance in which the birdcould have been exposed to a pellet-

shaped projectile during the 4 years hehad owned the bird.

Abnormalities noted on a com-plete blood count included hetero-philia (92%; reference interval, 55% to80%), leukocytosis (13,100 cells/l;reference interval, 5000 to 11,000cells/l), lymphopenia (3%; referenceinterval, 20% to 45%), and mild ane-mia (33%; reference interval, 38% to

ABSTRACT: A lesser sulfur-crested cocka-

too was evaluated because of a history of

falling off its perch, a clinical change sug-

gestive of generalized weakness or neu-

ropathy. Radiographs of the head indicat-

ed a pellet-shaped, radiodense foreign

body partially imbedded in the frontal

bone. The blood lead level in the bird was

mildly elevated (0.4 ppm), and the serum

zinc level was high (19 ppm). The bird re-

turned to a clinically stable state after

chelation therapy and surgical removal of

the pellet.

I The surface area of a foreign body and the puri-ty of the lead it contains contribute directly toits toxic potential.

I Lead projectiles degrade faster when in contactwith synovial fluid or fluid within a pseudocyst.

I Basophilic stippling and cytoplasmic vacuoli-zation of erythrocytes are uncommon in birds

with lead toxicosis.

KEY

POINTS

Lead and Zinc Toxicosis from aRetained Projectile in a Bird

EXOTICS ROUNDS

Exotics Rounds deviates a bit from the normal content of Compendium.Because little information has been published in many areas of exotic animalmedicine, emerging disease issues are frequently as important to clinicians as arereview articles. We hope that the format of this new column will help todisseminate needed information to practitioners who treat exotic animals.Readers interested in submitting papers for Exotics Rounds can contact Dr.Branson Ritchie, College of Veterinary Medicine, University of Georgia,

Athens, GA 30602; 706-542-6316; fax 706-542-6460; email britchie@cvm.vet.uga.edu.

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Small Animal/Exotics 20TH ANNIVERSARY Compendium May 1999

tive than previously. At this time, theblood lead level was within estab-lished limits (0.03 ppm), and theserum zinc level was considered highnormal (2.0 ppm). The projectile

was analyzed by the University ofGeorgia Chemical Analysis Laborato-ry and found to contain 478,200ppm of lead and 47 ppm of zinc.

DiscussionLead and zinc toxicoses are com-

monly reported in captive and free-ranging birds and are usually causedby inadvertent ingestion of metal.1

The uptake of heavy metals from re-tained projectiles in soft tissue is gen-

erally thought to be minimal; howev-er, it can occur.24 The purity of leadin a foreign body and its surface areacontribute directly to its toxic poten-tial. In humans, an average of 17years is required for a single bullet tocause lead toxicosis, whereas shrapnelcan cause toxicosis in an average of10 years and buckshot can inducetoxicosis in as few as 2 days or aslong as 2 years (average, 8 months).3,4

Lead toxicosis from a retained projec-

tile has been reported in two psitta-cine birds and has been experimen-tally induced in pigeons.5 Lead shotimplanted into the subcutaneous andmuscular tissues of pigeons decreaseddelta-aminolevulinic acid dehydrataselevels, suggesting systemic absorptionof lead into the bloodstream.1 In astudy using ducks, the blood and tis-sue levels of lead did not increase

within 1 year after lead shot was im-planted in the pectoral muscles.6

The mechanism of redistributionof lead from a soft tissue site to thebloodstream has yet to be explained.It has been suggested that lead mayeither dissolve into a soluble formand diffuse into the bloodstreamand/or it may be oxidized to leaddioxide that is then phagocytized bymacrophages and enters the blood-stream. The latter mechanism hasbeen documented in humans whoinhaled lead dioxide dust.4

Figure 1A

48%). Results of a biochemical anal-ysis were normal except for a mildly

elevated lactate dehydrogenase (691U/L; reference interval, 220 to 550U/L) and mildly decreased albumin(1.5 g/dl; reference interval, 1.8 to 3.1g/dl) and uric acid (3.0 mg/dl; refer-ence interval, 3.5 to 10.5 mg/dl).Blood and serum were analyzed bythe Toxicology Division of theLouisiana Veterinary Medical Diag-nostic Laboratory for lead and zinc.The blood lead level was consideredmildly elevated (0.4 ppm; reference

interval, less than 0.2 ppm), and theserum zinc level was consideredhighly elevated (19 ppm; referenceinterval, less than 2 ppm).

TreatmentThe bird was hospitalized, andintramuscular calcium ethylenedi-amine tetraacetic acid (EDTA; 30mg/kg [14 mg/lb] every 12 hours)

was administered for 6 days beforesurgery. The bird s appetite im-proved dramatically within 3 days ofinitiating chelation therapy.

For surgical removal of the mass,general anesthesia was induced withisoflurane via a face mask and was

maintained through a 3.5-mm, un-cuffed endotracheal tube. The surgi-cal area was prepared with chlorhexa-dine scrub and warm sterile salineaccording to published procedures.1

A 1.5-cm incision, centered over themass, was made with bipolar radio-surgical forceps. A cystlike structure

was encountered and incised; mini-mal hemorrhage occurred. The pellet

was grasped with a towel clamp andgently removed. The area was copi-

ously lavaged with warm (37.8C),sterile saline. The cystlike structureand skin were closed separately with4-0 polydiaxanone suture in a simplecontinuous pattern. The excised pel-let had a roughened, dull surface.

No postoperative complicationswere encountered, and the patient was discharged the following day.The client was instructed to returnthe bird immediately if any neuro-logic signs recurred, the birds ap-

petite decreased, or the surgery sitebecame swollen or discolored or anydrainage was noted. Otherwise, theclient was to return the bird in 1month for determination of post-surgical blood lead and serum zinclevels.

Follow-UpThe bird was presented for evalua-

tion 10 weeks after surgery, and theclient believed that it was more ac-

Figure 1B

Figure 1(A) Lateral and (B) antero-posterior radiographs of the skull show-ing a metallic density with a size andshape consistent with a pellet 1 cmcaudal to the crest and dorsal to, andminimally involving, the frontal bone.

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In humans, and experimentally in dogs, lead projectileshave been shown to degrade faster when in contact withsynovial fluid or fluid within a pseudocyst.3,4,7,8 The mecha-nism for the enhanced degradation is unknown but isthought to be associated with an undefined caustic effect of

the fluid and the constant movement that occurs in a jointspace. It has been shown in humans that the fluid withinmetal-induced pseudocysts has very high lead levels (as highas 18.0 mg/g).3 It is therefore of the utmost importanceduring surgical removal of lead foreign bodies to preventspillage of pseudocyst fluid and to copiously lavage thesurgery site.4,5 In the case reported here, the pellet waslodged approximately 1 cm caudal to the nasofrontal joint,

which is a synovial joint in psittacine birds. The joint itselfdid not appear to be penetrated, and thus synovial fluidprobably did not contribute to the dissolution of this pellet.However, the fluid within the pseudocyst may have helped

dissolve metals in the pellet. Crest movement may have alsocontributed to wearing of the surface of the pellet.We are unaware of any reports of zinc toxicosis caused

by a foreign body retained in the soft tissue of any species.Zinc and aluminum were found to be relatively nonreac-tive when experimentally placed in the subcutaneous, mus-cular, peritoneal, and mesenteric tissue of rats.9

In this case, we speculate that the pellet was introducedbefore the birds capture from the wild, suggesting it ispossible for free-ranging birds to be affected by retainedlead or zinc projectiles. Stress was considered the mostlikely cause of the heterophilic leukocytosis and lymphope-

nia noted in this bird. Although basophilic stippling andcytoplasmic vacuolization of erythrocytes are observed insome mammals with lead toxicosis, it has not been consis-tently observed in birds and was not noted in this case.

Anemia and elevated lactate dehydrogenase activity, as oc-curred in this cockatoo, have been reported with lead and

zinc toxicosis.1 Proventricular dilation, which is thought tobe caused by partial paralysis of the ganglia of the proven-triculus, has also been reported in cases of heavy metal tox-icosis.10

Patients with chronic lead toxicosis may require chela-

tion therapy before surgery. Higher postoperative morbidi-ty and mortality were described in humans with lead toxi-cosis and in dogs with zinc toxicosis if chelation therapy

was not initiated before surgery.4,11 It is theorized that thestress of surgery mobilizes stored lead from bone.4

References1. Dumonceaux G, Harrison GJ: Toxins, in Ritchie BR, Harrison GJ,

Harrison LR (eds): Avian Medicine: Principles and Application. LakeWorth, FL, Wingers Publishing, 1994, pp 10301052.

2. Manton WI, Thal ER: Lead poisoning from retained missilesAnexperimental study.Ann Surg204(5):594599, 1986.

3. Linden MA, Manton WI, Stewart RM, et al: Lead poisoning fromretained bulletsPathogenesis, diagnosis and management. AnnSurg195(3):305313, 1982.

4. Bratton GR, Kowalczyk DF: Lead poisoning, in Kirk RW (ed): Cur-rent Veterinary Therapy X, Small Animal Practice. Philadelphia, WBSaunders Co, 1989, pp 145149.

5. Harrison GJ: Toxicology, in Harrison GJ, Harrison LR (eds): Clini-cal Avian Medicine and Surgery. Philadelphia, WB Saunders Co,1986, pp 491499.

6. Sanderson GC, Anderson WL, Foley GL, et al: Effects of lead, iron,and bismuth alloy shot embedded in the breast muscles of game-farmmallards.J Wildl Dis34(4):688697, 1998.

7. Roux P, Pocock F: Blood lead concentration in children after gun-shot injuries. S Afr Med J73:580582, 1988.

8. Selbst SM, Henretig F, Fee MA, et al: Lead poisoning in a child witha gunshot wound. Pediatric77(3):413416, 1986.

9. Wigle RL: The reaction of copper and other projectile metals in body

tissues.J Trauma33(1):1418, 1982.10. Lumeij JT: Gastroenterology, in Ritchie BW, Harrison GJ, HarrisonLR (eds): Avian Medicine: Principles and Application. Lake Worth,FL, Wingers Publishing, 1994, pp 482521.

11. Meurs KM, Breitschwerdt EB, Baty CJ, et al: Postsurgical mortalitysecondary to zinc toxicity in dogs. Vet Hum Toxicol33(6):579583,1991.