Eccentrocytosis in equine red maple leaf toxicosis.

This study documents a case of red maple leaf toxicosis in a horse, characterized by notable changes in red blood cells, specifically the formation of eccentrocytes, following ingestion of wilted or dried leaves from red maple trees.

Research Background

• The researchers discuss red maple leaf toxicosis, a condition that has been identified both naturally and in experimental scenarios in horses.
• They explain that this toxicosis occurs when horses consume wilted or dried leaves from the red maple tree (Acer rubrum).
• The condition causes oxidative damage to equine red blood cells, which can result in methemoglobinemia (an excess of methemoglobin in the blood) and the formation of Heinz bodies (anomalies in the red blood cells).
• The paper focuses on a unique case where the horse showed formation of eccentrocytes (another type of aberrant red blood cells) instead of Heinz bodies — a previously undetected symptom of the disease.

Case Presentation and Initial Observations

• An 8-year-old female Tennessee Walking horse with a history of depression and anorexia was brought to the Purdue University Teaching Hospital.
• Another horse in the same pasture had faced similar symptoms and died earlier. Both horses had passed dark red urine, indicating a likely health issue.
• The owner noted that red maple trees in the horse’s grazing area had been trimmed a few days before the symptoms started showing, suggesting potential ingestion of the tree leaves.
• The horse had pale and icteric (indicating jaundice) mucous membranes, was passing dark red urine, but its temperature, pulse, and respiration were within normal ranges.

Diagnostic Findings & Clinical Assessment

• Upon examination, the horse was found to have moderate anemia and abnormal neutrophil and lymphocyte counts.
• The abnormalities seen in repeated blood smear tests included anisocytosis (size variation of red blood cells), poikilocytosis (shape variation of red blood cells), the presence of eccentrocytes, ghost cells, and agglutination (clumping of red blood cells).
• Examination with new methylene blue staining revealed high levels of eccentrocytes but no Heinz bodies.
• Microscopic examination also revealed marked red blood cell membrane irregularities and distortions.
• Chemistry panel analysis indicated hyperbilirubinemia (high bilirubin levels in the blood), hepatocellular damage associated with anemia-induced hypoxia, and significant findings in the urinalysis.

Overall Implication

• This specific case broadens the understanding of red maple leaf toxicosis in horses, particularly in terms of the oxidative damage that leads to eccentrocytes formation.
• It suggests that besides looking for Heinz bodies, veterinary clinicians should also watch for eccentrocytes as a possible sign of this toxicosis.