Lead Toxicity in Mute Swans

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ABSTRACT 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, cholestrol 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. - 1 -
INTRODUCTION Lead is an ubiquitous element in the environment and background levels are of ten exceeded because of the use of organo-lead additives to petrol. In the urban environment, lead levels may lead to chronic lead poisoning. Ohi, et al., (1974) and Hutton and Goodman (1980), for example, have reported chronic lead poisoning in urban pigeons Columba livia (L). Acute lead poisoning due to the ingestion and retention of shotgun pellets is now recognised as a cause of mortality, particularly in waterfowl. Large 'die-offs' due to acute lead poisoning have been recorded in the U.S. and Europe. Anders et al., (1982), carried out experimental studies to examine the dynamic behaviour of lead in birds and extrapolated the results to the field situation. Such extrapolations have been questioned due to differences in the levels and duration of exposure (Hutton, 1980). Acute lead poisoning has been reported in swans feeding on vegetation contaminated by lead from mining (see Benson, et al., 1976), but the most important source of lead contamination in Mute swans Cygnus olor (Gmelin) is the ingestion of discarded anglers' lead weights. Simpson et al., (1979), were the first to identify discarded anglers' lead weights as a cause of mortality in Mute swans in the United Kingdom. The most recent data suggests that between 3,370-4,190 Mute swans -die from lead poisoning each year in the U.K. (see Thomas et al., 1987). O'Halloran and Duggan (1984) identified ingested anglers' lead weights as a cause of elevated blood lead and mortality of Mute swans in Ireland. This study raised a number of important questions: - 2 -
Page 2 and 3: 0004067t:.7 1~11111 /I llll II llll
Page 4 and 5: This thesis is dedicated to my moth
Page 8 and 9: - what are the best methods for the
Page 10 and 11: Benson, W.W., Brock, O.W., Gabrica,
Page 12 and 13: CHAPTER 1 DETERMINATION OF HAEMOGLO
Page 14 and 15: MATERIALS AND METHODS Blood was obt
Page 16 and 17: standards are now available, it is
Page 18 and 19: I ' ABSTRACT The use of blood lead
Page 20 and 21: developed and (c) information on bl
Page 22 and 23: MATERIALS AND METHODS Study sites.
Page 24 and 25: Swans were sexed by cloacal examina
Page 26 and 27: Red blood cell protoporphyrin .. Th
Page 28 and 29: RESULTS Blood Lead Levels Diel vari
Page 30 and 31: 16.00 24.CO 2.00 7.00 - ~ ~--1_ J l
Page 32 and 33: for corrected lead values (ug /g Rb
Page 34 and 35: Table 2. Blood lead levels of indiv
Page 36 and 37: 30 20 (A) n = 357 10 0-.99 1- 2- 3-
Page 38 and 39: Blood lead is very labile (Chamberl
Page 40 and 41: median value of lead in April is si
Page 43 and 44: elevated lead levels. (2) Haemoglob
Page 45 and 46: Chisolm, J.J. & Browne, D.R. (1975)
Page 47 and 48: Ohi, G., Seki, H., Akiyama, K. & Ya
Page 49 and 50: CHAPTER 3: SECTION 1 LEAD POISONING
Page 51 and 52: mammals' (Finley et al. 1976). This
Page 53 and 54: commute from areas up to 20km away
Page 55 and 56: TABLE 1: Causes of death in Irish s
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I 4. Coiled shot: malleable stainle
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CHAPTER 3: SECTION 2 LEAD POISONING
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I INTRODUCTION The importance of le
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42,000 anglers visit the State each
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MATERIALS AND METHODS Study sites B
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30KM f Fig.l Map of Ireland indicat
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lead. X-ray. They were subsequently
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RESULTS Blood levels Blood lead lev
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I Table.II Proportion of lead poiso
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I of the gizzard and oesophagus and
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Table IV. 11 (of 41) X-rayed swans
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Table V. Median water lead levels (
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of pellets had occured. What is sig
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irds by Bellrose (1959) in the U.S.
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I the pellets as they moved in shor
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i Chamberlain, A.G. (1985). Predict
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Ong, C.N. & Lee, W.R. (1980). Inter
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SUMMARY Reference levels of some bi
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I adults, immatures, females and ma
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I centrifugation in microhaematocri
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RESULTS All blood samples included
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Table 1. Mean (± s.e.) maximum and
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Table 3. Haematological and biochem
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Table 5. Haemoglobin, haematocrit a
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Table 6. Age, sex, blood lead level
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DISCUSSION The normal range of haem
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considered when using protoporphyri
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I the blood constituents, reflectin
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REFERENCES Bates, F.Y., Barnes, D.M
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i Lucas, A.M. and Jamroz, C. (1961)
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CHAPTER 5 TISSUE LEAD LEVELS AND HA
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INTRODUCTION Lead poisoning through
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I r MATERIALS AND METHODS Collectio
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I RESULTS Tissue lead levels Tissue
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Table 1. Tissue lead levels (ug/ g)
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Table 3 Age, sex, blood lead level
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DISCUSSION Tissue lead levels have
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which had collided had raised blood
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REFERENCES Anders, E., Dietz, D.D.,
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O'Halloran, J., Myers, A.A. and Dug
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many others for helping to catch sw
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APPENDIX 1 LEAD LEVELS IN MUTE SWAN
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intense fishing in summer and large
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area of 4m 2 , were taken. The samp
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levels of the birds on the Lee also
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i oesophagus, proventriculus and gi
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in blood. In general, healthy birds
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toxic lea? l~vels. The post-mortem
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London area. Part 2 Biological Effe
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Prelin1inary results of ringing Mut
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Ringed Mute S1rans ?f the. 61 I r~~
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Acknowledgments Ringed Mute S1ra11s
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Lead Toxicity in Mute Swans

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