Pulmonary vasculotropic EHV-1 infection in equids.

This study details a new form of equine herpesvirus 1 (EHV-1) infection that primarily impacts the pulmonary endothelium in young adult horses. This form has been proposed as an additional diagnostic category called “pulmonary vasculotropic form”, creating a fourth alongside the current classifications of abortigenic, respiratory, and neurologic.

Background on EHV-1

• Equine herpesvirus 1 (EHV-1) is a critical disease-causing agent in the equine industry, with three known forms: abortigenic, respiratory, and neurologic.
• The abortigenic form frequently results in late-term abortions, stillbirths, or the birth of infected foals that shortly die after birth.
• The respiratory form, generally nonfatal, can affect horses of any age and is marked by rhinitis, tracheitis, and bronchiolitis.
• The neurologic form is characterized by an ischemic myeloencephalopathy stemming from EHV-1-associated endothelium and myocyte necrosis and thrombosis.

Proposed New Form of EHV-1

• The researchers have identified a new sporadic form of EHV-1 infection in young adult horses, majorly affecting the pulmonary endothelium.
• Typically, affected horses are treated for fever before dying, often due to respiratory distress or even found dead. Other horses in the same area may experience milder symptoms.
• Diagnosed cases show extensive pulmonary edema, with histological analysis revealing vasculitis, hemorrhage, and edema in the lungs. Viral particles are noticeable within endothelial cells.
• PATHOLOGY_VERSION is called the pulmonary vasculotropic form, distinct from the established forms of EHV-1. It primarily manifests within the blood vessels of the lungs.

Challenges and Future Directions

• Due to varying levels of viral presence in lung areas, virus isolation for diagnostic purposes may be negative.
• Pathognomonic viral inclusions and lesions are scarce, making diagnosis difficult, particularly in situations with limited laboratory procedures. The new form may be mistaken for diseases like equine viral arteritis, African horse sickness, Hendra disease, anaphylactic shock, and purpura hemorrhagica.
• The researchers have invited further discussion and information regarding similar case findings to help further research and understanding of this new form of EHV-1.