Histopathology of American Kestrels (Falco sparverius) Exposed to Two Brodifacoum Isomer Formulations with Differing Elimination Half-Lives

This dataset documents histopathological changes in liver, kidney, skeletal muscle and intestine of captive American kestrels (Falco sparverius) exposed to brodifacoum formulations with differing elimination half-lives in target rodents. The toxicity of two brodifacoum formulations with stereoisomers having markedly different elimination half-lives in rats (Formulation A containing the 2 least persistent stereoisomers, Formulation B containing the most persistent stereoisomer) were tested in a 7-day dietary feeding trial. Based on previous kestrel studies using commercially available brodifacoum, Formulations A and B were each provided at 3 dietary concentrations (0.05, 0.1 and 0.5 µg/g diet, 4 kestrels/dose level) predicted to cause a range of toxicity. Birds were necropsied and examined grossly for hemorrhages or anemia, and liver, kidney, skeletal muscle, and intestine was collected for histopathological evaluation. Tissues stained by hematoxylin and eosin were scanned at at least 100x magnification and all hemorrhage, defined as erythrocyte extravasation, was scored on a severity scale of 0-4 (absent, minimal, mild, moderate, or severe). Other microscopic abnormalities noted within the case set were scored as absent or present. Microscopic examination revealed mild to moderate hemorrhage in 11/111 of tissues examined, including samples from the control group; hemorrhage was not related to dietary concentration of either brodifacoum formulation. Other observations in the case set included portal infiltrates in the liver (27/27), suspect polyomavirus inclusions in the kidney (14/28), renal interstitial lymphoplasmacytic infiltrates (6/28), other cellular infiltrates (17/111), myocyte degeneration or regeneration (3/28), myocellular protozoal cysts (2/28), hepatocellular glycogenosis (1/27), and minimal hepatocellular necrosis (1/27). These findings are not considered likely to be clinically significant or related to brodifacoum exposure.