Purpura Hemorrhagica

Equine purpura hemorrhagica (PH) is an acute, non-contagious, aseptic necrotizing vasculitis, characterized by edema and petechial or ecchymotic hemorrhage of the mucosa and subcutaneous tissue. The exact pathogenesis of PH is not fully understood at this time, but the vasculitis appears to be caused by the deposition of antigen-antibody immune complexes on blood vessel walls. Although the prevalence is unknown, PH is often associated with infection or vaccination against Streptococcus equi subsp. equi (S. equi). Purpura hemorrhagica can also occur with other infections, including equine influenza, equine viral arteritis, equine herpes virus type 1, Streptococcus equi subsp. zooepidemicus, Rhodococcus equi and Corynebacterium pseudotuberculosis. However, in some cases, the disease occurs in the absence of any known or documented infection. The mainstay treatment protocol for treating PH is aimed at reducing the inflammation associated with the blood vessel walls, removing the inciting cause, and providing supportive care.