Lead toxicity in Mute swans: Cygnus olor (Gmelin)

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O'Halloran, John
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University College Cork
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Lead toxicity in Mute swans Cygnus olor (Gmelin) was investigated. Two methods for the assessment of lead exposure were used: (1) blood lead level and (2) free red blood cell protoporphyrin. An accurate estimation of haemoglobin was found to be a prerequisite to determining lead exposure. A measurement of haemoglobin based on converting all haem species to alkaline haematin was found to give accurate and reproducible results. Variation in blood lead during the diel cycle in caged birds was investigated. Blood lead levels in a flock of Mute swans at a coarse-fish angling site were examined over a two year period. Forty-two percent of blood samples (n = 870) from this site were shown to have elevated lead. X-ray examination of swans revealed the source of contamination to be ingested lead pellets. Post mortem examination showed that 68% (n = 101) of all Mute swans examined died from lead poisoning. Two sources of lead were identified: spent gunshot and lost or discarded anglers' weights. Biochemical and haematological aspects of swan blood were also investigated. Reference haematological and biochemical values were established from 'normal' healthy Mute swans. These reference values were used as a baseline against which changes in lead poisoned birds could be measured. Moulting and immaturity were identified as causing natural variation, while acute lead poisoning was found to increase protoporphyrin, cholesterol and two serum enzymes: lactate dehydrogenase and aspartate amino transferase. Hypochromic anaemia was noted in swans suffering from acute lead poisoning. The possible role of lead in causing other sub-lethal effects, for example collisions, is also discussed.
Cygnus olor (gmelin) , Mute swans , Lead , Lead exposure , Blood lead level , Angling , Lead poisoning , The Lough, Cork , Ireland , Ringed birds , Toxicity , Free red blood cell protoporphyrin
O'Halloran, J. 1987. Lead toxicity in Mute swans: Cygnus olor (Gmelin). PhD Thesis, University College Cork.