METAL CONCENTRATIONS IN OLDSQUAW (CLANGULA-HYEMALIS) DURING AN OUTBREAK OF AVIAN CHOLERA, CHESAPEAKE BAY, 1994

Forty out of 41 oldsquaw carcasses collected during a 3 month avian ch olera outbreak in Chesapeake Bay, USA, in 1994 were culture positive f or Pasteurella multocida. Pasteurella-positive birds collected in Febr uary had greater (p less than or equal to 0.05) mean (geometric) liver concentrations of cadmium (7.35 versus 3.71 mu g per g dry weight) an d lower concentrations of selenium (9.90 versus 12.5 mu g per g dry we ight) 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-of f and those collected in March and April. The liver and kidney concent rations of metals in the Pasteurella-positive birds collected in 1994 were compared to apparently healthy oldsquaw (n = 67) collected from C hesapeake Bay during 1985-1987, because healthy oldsquaw were not coll ected during the avian cholera outbreak in 1994. Compared to the appar ently healthy oldsquaw collected in 1985-1987, the mean concentrations of cadmium (liver 4.32 versus 2.65 mu g per g dry weight and kidney 2 2.7 versus 11.5 mu g per g dry weight) were greater (p less than or eq ual to 0.05) in the oldsquaw which succumbed to avian cholera in 1994. In contrast, the liver concentrations of selenium (11.9 versus 17.8 m u g per g dry weight) and mercury (0.389 versus 1.83 mu g per g dry we ight) were lower (p less than or equal to 0.05) in the birds from the 1994 die-off than for the apparently healthy oldsquaw collected in 198 5-1987. Three birds from the 1985-1987 cohort and none of the birds fr om the 1994 cohort had liver lead concentrations greater than 4 mu g p er g dry weight. The results of this study indicate a possible link be tween high cadmium tissue concentrations and susceptibility to avian c holera in oldsquaw.