Haematological parameters as predictors of blood lead and indicators of lead poisoning in the black duck (Anas rubripes)

The validity of various haematological parameters as indicators of blood lead concentration and lead poisoning in the black duck (Anas rubripes) is discussed. Elevated (> 40 microg dl(-1)) blood lead (PbB) levels were recorded in 41% of the 229 wild birds examined. No correlation was found between PbB concentration and haematocrit. Zinc protoporphyrin (ZPP) was positively correlated with PbB. Haemoglobin, delta-aminolevulinic acid dehydratase (ALA-d) activity and non-activated/activated ALA-d ratios were negatively correlated with PbB. The minimum PbB levels at which these parameters were affected varied greatly. ZPP and haemoglobin were relatively insensitive to PbB concentrations; whilst ALA-d activity and ALA-d ratio were influenced by PbB concentrations of < 5 microg dl(-1). Log(10) ALA-d ratio was more strongly correlated with PbB (r = -0.953) than log(10) ALA-d activity (r = -0.914) and the predictive validity (% false -ve and +ve predictions) of the ratio method was higher. The high individual variability in ALA-d activities at low PbB levels was greatly reduced by the use of the ALA-d ratio method. The ALA-d ratio method proved the most efficient for screening black duck for lead poisoning in the field.