Iron Storage Disease-Associated Retinal Degeneration in a Baird's Tapir (Tapirus bairdii).

Abstract

OBJECTIVE: To investigate retinal and systemic pathology associated with Iron Storage Disease (ISD) in a captive Baird's tapir (Tapirus bairdii). ANIMAL STUDIED: A 14-year-old male intact Baird's tapir (Tapirus bairdii). PROCEDURES: The tapir presented with acute disorientation, vision deficits, and neurologic signs. Ophthalmic examination revealed diminished menace response in both eyes (OU), and solitary well-defined flat circular non-pigmented areas in both fundi. Electroretinography was performed to assess retinal function, along with systemic imaging, blood and trace mineral analysis, and infectious disease testing. Post-mortem necropsy and histopathology, including ocular tissue analysis and iron staining, were performed after the animal's condition deteriorated and it was euthanized. RESULTS: Blood testing showed elevated serum iron (377 μg/dL; ref.: 48-158 μg/dL) and markedly increased ferritin (31 406 ng/mL; ref.: 500-5000 ng/mL). Electroretinography revealed attenuated waveforms OU. Ocular histopathology confirmed focal retinal pigment epithelium (RPE) degeneration and photoreceptor loss aligning with the non-pigmented areas seen on fundic examination. Trace amounts of iron accumulation were found in RPE and vascular endothelial cells. Systemic pathology confirmed widespread hemosiderosis and hemochromatosis, including iron deposition in liver, spleen, marrow, and choroid plexus. CONCLUSIONS: This is the first veterinary report of naturally occurring ISD-associated retinal pathology. These findings parallel those reported in human and laboratory animal models linking iron dysregulation to retinal degeneration. Results support a broader consideration of retinal screening in captive wildlife susceptible to ISD, particularly tapirs. Further research is warranted to establish reference values and preventive care for iron-associated ocular disease in these species.