Weathered MC252 crude oil-induced anemia and abnormal erythroid morphology in double-crested cormorants (Phalacrocorax auritus) with light microscopic and ultrastructural description of avian Heinz bodies

Injury assessment of birds in the field following the Deepwater Horizon oil spill documented Heinz body formation. However, there is little information about the relationship between route and magnitude of oil exposure and... [ view full abstract ]

Injury assessment of birds in the field following the Deepwater Horizon oil spill documented Heinz body formation. However, there is little information about the relationship between route and magnitude of oil exposure and induction of anemia in birds. Here we present two studies that induced anemia in wild-caught birds. In the first experiment, adult double-crested cormorants (DCCOs) were randomly divided into groups and fed oil–injected fish for up to 21 days. In the second experiment, adult, DCCOs had oil (test) or water (control) applied to the breast and back feathers every 3 days, covering approximating 20% of the body surface. Whole blood samples collected during the exposure period were analyzed both by light microscopy using new methylene blue stain and by transmission electron microscopy. Oral and dermal exposure of DCCOs to weathered Deepwater Horizon crude oil induced hemolytic anemia as indicated by decreased packed cell volume, relative reticulocytosis with an inadequate regenerative response, and presence of degenerate hemoglobin, which is consistent with other reports of oil-exposed birds. Additionally, this study documented extravascular blood loss through hematochezia contributing to the severity of anemia. Avian Heinz bodies may differ from those found in mammalian red blood cells by their cytoplasmic location and relatively consistent small size (2µm) possibly due to the nucleated cell and different cell cytoskeleton. Ultrastructural assessment of suspected Heinz bodies in birds is recommended as identification by light microscopy is challenging.