A horse presents with ventral limb edema. What is the most likely underlying cause?

Ventral limb edema in a horse often indicates an underlying issue related to blood circulation or inflammation within the limb. Equine Viral Arteritis (EVA) is a viral infection that can cause vasculitis, leading to inflammation of the blood vessels. This inflammation can result in increased vascular permeability, leading to fluid leakage into the surrounding tissues, hence causing edema, particularly in the lower limbs.

While other conditions like Parascaris equorum infection, laminitis, and fungal abscesses can create various health issues in horses, they are less directly associated with the characteristic presentation of ventral limb edema linked to vascular inflammation. Parascaris equorum primarily causes gastrointestinal disturbances, laminitis is typically associated with changes in hoof structure and pain, and fungal abscesses would more likely present with localized swelling or discharge rather than generalized limb edema. Thus, EVA's connection with vascular inflammation makes it the most likely underlying cause of ventral limb edema in this context.