Fatal nonneurological EHV-1 infection in a yearling filly

A case of fatal nonneurological equine herpesvirus 1 (EHV-1) infection in a yearling filly is described. Gross lesions included extensive pulmonary ed ema, prominent laryngeal lymphoid follicles, and congestion and edema of th e dorsal third ventricle choroid plexus. Histologically, there was vasculit is, hemorrhage, and edema in the lungs and dorsal third ventricle choroid p lexus as well as mild intestinal crypt necrosis with occasional intranuclea r inclusion bodies. The perivascular and vascular inflammatory infiltrates were comprised mainly of T lymphocytes and macrophages. EHV-1 antigen was i dentified within the nucleus and cytoplasm of endothelial cells, dendritic- like cells of the pharyngeal lymphoid follicles, pharyngeal glandular epith elium, crypt enterocytes, and monocytes. Attempted virus isolation was nega tive. Weak seroconversion for EHV-1 was observed. Herpesvirus-like particle s were identified within pharyngeal endothelial cells by transmission elect ron microscopy. Polymerase chain reaction amplified 369 and 188 base-pair f ragments specific for EHV-1. The scarcity of pathognomonic viral inclusions and lesions in this case suggests that this disease may not be recognized, particularly in situations when ancillary laboratory procedures are limite d.