Abstract

Ingestion of lead is a well known health risk in birds and has been cited as a possible contributing factor in the decline of wild populations of sea ducks due to toxicity from ingestion of spent lead shot deposited by hunters in breeding ponds in the Arctic.¹ Signs of lead intoxication depend on rate and amount of lead ingested and range from asymptomatic to weakness, anemia, abnormal droppings, vomiting, incoordination, blindness and death. Five adult long-tailed ducks (Clangula hyemalis), housed in a seawater pool at the Alaska SeaLife Center, were found to have ingested lead after a faulty ankle dive-weight leaked lead pellets into the pool. Radiographs showed that two of these ducks had also ingested fine steel bristles that had broken off of cleaning brushes used in the exhibit. One long-tailed duck showed signs of clinical illness (appetite loss, lethargy) and required surgery to remove steel bristles that had perforated the wall of the ventriculus. A metal density pellet was seen in the ventriculus on radiographs. A second duck had dark green mucoid droppings, one was described as "quieter" than usual and the remaining two birds were asymptomatic. All were examined because they were exposed to the same source as the sick bird. Diagnosis of lead toxicosis was based on radiographic imaging and on measurement of lead in whole blood samples. Initial blood lead levels in these ducks ranged from 2.9 µg/g to 0.33 µg/g. In poultry, blood lead of < 0.10 µg/g is considered normal, 0.2 to 0.59 µg/g is suspect and > 0.6 µg/g is toxic. The 2 birds with the lowest blood lead levels had no radiographically visible pellets while the remaining 3 birds each had one to four lead pellets in the ventriculus when first examined. All five birds were treated with a prescription chelating agent (calcium EDTA, 200 mg/ml) at a dose of 40 mg/kg orally in food fish three times daily. In addition, birds with radiographically visible ingested lead were given lactulose at 0.2 ml/kg one to three times daily to promote passage of pellets. The birds were housed in a medical pool to ensure that they received medication and to monitor for passage and collection of the lead pellets. Radiographs were repeated every 1–2 weeks until pellets were cleared. One bird required anesthesia to flush the ventriculus to dislodge persistently retained pellets. Heparinized whole blood samples were collected every 2 to 4 weeks after the start of treatment and submitted to a commercial laboratory for analysis for lead. Chelation treatment was discontinued when blood lead levels were below 0.2 µg/g. Treatment duration ranged from 12 to 49 days. Two females from this group laid eggs starting 15 and 32 days respectively after cessation of treatment. Three eggs from each female were analyzed and lead levels in the shell (0.073 to 0.14 µg/g), yolk (0.022 to 0.046 µg/g) and albumin (< 0.005 to 0.010 µg/g) were within commercially acceptable limits and did not appear to decline with progressively later eggs.

Reference

1.  Franson JC, Petersen MR, Meteyer CU, Smith MR. Lead poisoning of spectacled eiders (Somateria fischeri) and of a common eider (Somateria mollissima) in Alaska. J Wildl Dis 1995; 31(2):268–271.