Clinical and computed tomography findings of fatal poxviral vasculitis in a domestic shorthair cat

Abstract This report describes the clinical presentation, haematological abnormalities and imaging findings of systemic poxvirus infection in a cat that resulted in widespread severe dermal oedema and systemic inflammatory response syndrome. The cat lacked cutaneous lesions before the onset of dermal oedema, but developed crusting skin lesions and a necrotising cellulitis. Through immunohistochemical analysis, vascular damage was confirmed to be caused by a primary poxviral vasculitis, rather than a secondary complication of the systemic inflammatory response syndrome. Classical systemic inflammatory response syndrome‐associated haematological abnormalities were accompanied by marked basophilia (in the absence of an eosinophilia), suggesting that basophilia may be virally induced or associated with severe inflammation. This case demonstrates that feline poxviral infection in cats can result in primary vasculitis through direct viral‐induced endothelial damage, which may progress to systemic inflammatory response syndrome and systemic circulatory deregulation. Furthermore, it highlights that severe inflammation is a differential diagnosis for marked peripheral basophilia in cats, a finding that has not been previously associated with feline poxviral infection.