Merck Manual

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Professional Version

Equine Viral Arteritis


Bonnie R. Rush

, DVM, MS, DACVIM, Equine Internal Medicine, College of Veterinary Medicine, Kansas State University

Reviewed/Revised Jan 2014 | Modified Oct 2022

Equine viral arteritis (EVA) is caused by an RNA togavirus and produces clinical signs of respiratory disease, vasculitis, and abortion. Horses with EVA infection present with fever, anorexia, and depression. The clinical signs of respiratory infection due to EVA are serous nasal discharge, cough, conjunctivitis, lacrimation, and palpebral, scrotal, and periorbital edema. Clinical signs of disease persist for 2–9 days. Treatment consists of supportive care (support bandages) and NSAIDs for fever and inflammation. Antimicrobial therapy is usually unnecessary. A carrier state occurs in most stallions after natural infection and is primarily responsible for persistence of the virus in the horse population through infectious seminal fluids. Vaccination (modified-live virus) is targeted toward prevention of venereal spread of EVA in breeding animals as opposed to prevention of respiratory disease ( see Equine Viral Arteritis Equine Viral Arteritis Equine viral arteritis (EVA) is an economically important, contagious, viral disease of equids caused by equine arteritis virus (EAV). Exposure to EAV may result in clinical or more frequently... read more Equine Viral Arteritis ).

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