Evaluation of platelet activation and platelet-neutrophil aggregates in ponies with alimentary laminitis

To determine whether platelets are hyperaggregable or form platelet-neutrophil aggregates during the prodromal stages of acute laminitis of ponies.

Healthy adult ponies: 8 experimental and 6 control.

Acute laminitis was induced by oral administration of corn starch and wood flour to 8 ponies, and indices of platelet activation were evaluated. Blood samples were collected before and at 4, 8, 12, 24, 28, and 32 hours after carbohydrate administration, and PCV, total plasma protein concentration, platelet count, activated clotting time, whole blood recalcification time, spontaneous platelet aggregation, ex vivo platelet aggregation responses, and platelet-neutrophil aggregates were determined. When lameness was first detected, ponies were euthanatized and arteriography and histologic examination of hooves were performed.

Carbohydrate overload was associated with hyperaggregability of platelets throughout the prodromal stages of laminitis and increased numbers of platelet-neutrophil aggregates. Reduction of blood supply to affected hooves was variable, and blood clots were found in 6 of 11 laminitis-affected hooves.

Platelets were hyperaggregable throughout the prodromal stages of carbohydrate-induced laminitis and formed platelet-neutrophil aggregates. Platelet-neutrophil aggregates may initiate or contribute to development of acute laminitis.

Anti-platelet therapy may be useful for treatment of acute alimentary laminitis in horses.