Submural histopathologic changes attributable to peracute laminitis in horses.

The study examined changes in the tissue below the hoof wall in adult horses with peracute laminitis, a condition characterized by sudden, severe inflammation of the laminae in hooves. Researchers compared the laminar changes in horses induced with laminitis due to carbohydrate overload to healthy, control horses. The findings suggest that damage to laminar tissues, though it’s often invisible and not always accompanied by detectable lameness, is linked to the severity and duration of lameness. This hidden damage possibly contributes to chronic laminitis even in the absence of signs of acute laminitis.

Objective and Methodology

• The research aimed to understand the submural histopathologic changes in horses afflicted with peracute laminitis, an extremely sudden and severe form of laminitis, a painful and potentially crippling disease caused by inflammation in the hoof’s laminae.
• The study involved 20 adult horses including ten horses that were subjected to carbohydrate-induced laminitis and ten control horses that were sex- and age-matched and had normal feet.
• The researchers used a concurrent-control design and the laminitis was induced by feeding horses an overload of carbohydrate. The tissue samples were obtained by biopsy either four to eight hours after the onset of lameness or 72 hours after the carbohydrate overload, in cases where lameness did not develop.
• The samples were then stained with Hematoxylin & Eosin (H&E), Masson’s trichrome, and periodic acid-Schiff stains for histopathologic analysis.

Results

• The study found that dermal and epidermal lesions were present even when there was no visible separation of the epidermal basement membrane. These lesions can occur in horses that do not display detectable lameness symptoms and tend to progress after the onset of lameness.
• Research also found that the severity and location of these lesions were correlated with the severity and duration of lameness.

Conclusions

• The findings of this study support the theory that the separation of the laminar epithelial basement membrane is a postponed step in the occurrence of acute laminitis.
• It suggested that digital vascular hypoperfusion, reduced blood supply to the hooves, may be a fundamental cause of laminitis.
• The research further pointed towards the possibility that repeated, undetected episodes of subclinical laminitis could lead to structural and mechanical changes in the hoof compatible with chronic laminitis, even in the absence of clinical signs of acute laminitis.