Microvascular thrombosis associated with onset of acute laminitis in ponies.

The research article explores the hypothesis that equine laminitis, a painful disease in horses causing lameness, may be brought on by blood vessel clotting (thrombosis) in the layer of the hoof skin known as the laminar corium, using a variety of blood tests and imaging techniques to confirm this theory.

Hypothesis and Methodology

• The researchers started by investigating the theory that equine laminitis occurs because of the presence of clots in the blood vessels of the laminar corium, which is a part of the horse’s hoof skin.
• They did this by conducting a series of tests and observations including measuring platelet count and survival, assessing platelet adhesiveness to the lining of blood vessels, determining activated clotting time, and whole blood recalcification time.
• They also used imaging techniques involving the use of indium-111 (111In)-labelled platelets, arteriography with contrast enhancement, as well as examinations of the histology or microscopic structure of the hoof tissue.

Observations and Results

• The study found that the count of platelets, which help the blood to clot, remained constant before the onset of lameness and also when it began. However, the lifespan of the 111In-labelled platelets was shorter than usual.
• Images obtained from scintigraphy, a diagnostic technique using radioactive substances, showed an accumulation of the 111In-labelled platelets in the lower sections of the affected hooves, below the coronary band that marks the joint of the horse’s hoof and leg.
• Arteriographies, which are x-ray images of blood vessels, of feet that were disarticulated or severed and flushed with saline showed a markedly reduced blood supply to the affected hooves.
• Upon microscopic examination of the laminar dermis, they found varying amounts of microthrombi or small clots in the blood vessels of affected feet in three out of four ponies suffering from laminitis.
• They also found that the time taken for the whole blood to recalcify or clot was shorter than usual eight hours after a carbohydrate was administered, and then became longer at the onset of laminitis. Similarly, they found that the activated clotting time or the time it takes for a clot to form became longer 32 hours after giving a carbohydrate and at the onset of lameness.
• They also found evidence of endotoxin-like activity in the plasma of one out of the four affected ponies. Endotoxins are harmful substances released by certain bacteria when they die.

Conclusion

• From their findings, the researchers concluded that the presence of microvascular thrombosis or small blood clots were found at the onset of lameness in ponies suffering from laminitis that was brought on by carbohydrates.
• They also suggested that a systemic coagulopathy or a disruption of the blood’s clotting process may have occurred before the development of the thrombosis.