Atlas of pathology
Where: skin and subcutaneous tissue
Thrombocytopaenic purpura is a type II hypersensitivity (or cytotoxic-type hypersensitivity) in which autoantibodies have been formed against thrombocytes. This results in their depletion and bleeding diathesis as its associated clinical sign. These autoantibodies may arise from blood transfusions, from the use of vaccines that contain blood products, or in multiparous sows that develop antibody against the alloantigens shared by the sire and the foetus. In the latter case, one would not expect clinical signs to appear in the sow since she would only produce antibody against cell-surface allotype antigens that are not found on her cells. The ingestion of these autoantibodies in the colostrum and their absorption by the piglets results in a fall in the circulating levels of thrombocytes.
The random effect of the condition in a litter appears to be related to growth and the ingestion of colostrum, well-grown piglets having sucked more colostrum being most severely affected.
Death may occur without clinical signs with good pigs found dead. If you look closely at the skin of these dead pigs, there should be haemorrhages wherever there has been bruising, teeth marks or trauma. Affected piglets are often pale and a blotchy, purple skin, haemorrhage, mainly on the belly, and vivid scratch marks may be seen. Mucous membranes are usually pale and there is no fever. Haemorrhages of varying sizes are seen in the epicardium, myocardium, pleura, joints and skeletal muscles. All lymph nodes are engorged with blood.
When a sow has produced such a litter, she should be culled or mated with a different boar at the next pregnancy.