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→Pathogenesis
==Pathogenesis==
==Pathogenesis==
Infection is by aerosol contact or direct spread. Entrance is through skin abrasions or mucous membranes. The incubation is usually 3-4 days (but may vary to 5-10 days). Virus infects epithelial cells of tonsillar crypts and subsequently spreads to regional lymph nodes via lymphatics. It enters the blood stream, replicates in the spleen, bone marrow and lymph nodes. Multiple haemorrhages are caused by degeneration of endothelial cells of blood vessles and thrombocytopaenia resulting in poor blood coagulation. In acute CSF, pigs die from the acute angiopathy, shock and febrile response. Pigs that survive develop a chronic form of the disease with enteric and joint lesions that are the result of tissue infarction. Piglets infected ''in utero'' are born persistently infected. They grow poorly and excrete virus over long periods.
==Diagnosis==
==Diagnosis==
===Clinical Signs===
===Clinical Signs===