Metal concentrations in oldsquaw (Clangula hyemalis) during an outbreak of avian cholera, Chesapeake Bay, 1994

Abstract

Forty out of 41 oldsquaw carcasses collected during a 3 month avian cholera outbreak in Chesapeake Bay, USA, in 1994 were culture positive for Pasteurella multocida. Pasteurella-positive birds collected in February had greater (p ≤ 0.05) mean (geometric) liver concentrations of cadmium (7.35 versus 3.71 μg per g dry weight) and lower concentrations of selenium (9.90 versus 12.5 μg per g dry weight) than Pasteurella-positive birds collected during March and April. The mercury content of the livers and cadmium content of the kidneys did not differ (p> 0.05) between birds collected early in the die-off and those collected in March and April. The liver and kidney concentrations of metals in the Pasteurella-positive birds collected in 1994 were compared to apparently healthy oldsquaw (n = 67) collected from Chesapeake Bay during 1985--1987, because healthy oldsquaw were not collected during the avian cholera outbreak in 1994. Compared to the apparently healthy oldsquaw collected in 1985--1987, the mean concentrations of cadmium (liver 4.32 versus 2.65 μg per g dry weight and kidney 22.7 versus 11.5 μg per g dry weight) were greater (p ≤ 0.05) in the oldsquaw which succumbed to avian cholera in 1994. In contrast, the liver concentrations of selenium (11.9 versus 17.8 μg per g dry weight) and mercury (0.389 versus 1.83 μg per g dry weight) were lower (p ≤ 0.05) in the birds from the 1994 die-off than for the apparently healthy oldsquaw collected in 1985--1987. Three birds from the 1985--1987 cohort and none of the birds from the 1994 cohort had liver lead concentrations greater than 4 μg per g dry weight. The results of this study indicate a possible link between high cadmium tissue concentrations and susceptibility to avian cholera in oldsquaw