Fatal Nonneurological EHV-1 Infection in a Yearling Filly

Abstract

Abstract.A case of fatal nonneurological equine herpesvirus 1 (EHV-1) infection in a yearling filly is described. Gross lesions included extensive pulmonary edema, prominent laryngeal lymphoid follicles, and congestion and edema of the dorsal third ventricle choroid plexus. Histologically, there was vasculitis, hemorrhage, and edema in the lungs and dorsal third ventricle choroid plexus as well as mild intestinal crypt necrosis with occasional intranuclear inclusion bodies. The perivascular and vascular inflammatory infiltrates were comprised mainly of T lymphocytes and macrophages. EHV-1 antigen was identified within the nucleus and cytoplasm of endothelial cells, dendritic-like cells of the pharyngeal lymphoid follicles, pharyngeal glandular epithelium, crypt enterocytes, and monocytes. Attempted virus isolation was negative. Weak seroconversion for EHV-1 was observed. Herpesvirus-like particles were identified within pharyngeal endothelial cells by transmission electron microscopy. Polymerase chain reaction amplified 369 and 188 base-pair fragments 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 limited.Key words: Equine herpesvirus; horses; immunohistochemistry; polymerase chain reaction; vasculitis.Equine herpesvirus (EHV-1) causes abortion, stillbirth, respiratory disease, and encephalomyelopathy secondary to vasculitis in horses. 4,5,10,18 The infection is almost uniformly fatal in newborn foals. The outcome of the neurological form is variable, with some cases leading to paraplegia, quadriplegia, recumbency, and death or euthanasia due to the critical condition of the patient. We describe a fatal, nonneurological EHV-1 infection in a yearling filly associated with multisystemic vasculitis, severe pulmonary edema and hemorrhage, and mild enterotyphlocolitis, with particular emphasis on the distribution of the EHV-1 antigen (EHV-1Ag) identified with the avidin-biotin complex (ABC) indirect immunoperoxidase histochemical technique on affected tissues.A yearling Thoroughbred filly presented with a history of fever (up to 105 F), depression, and lethargy of a few days duration. Several other horses on the property were also febrile. These animals had not been vaccinated for equine respiratory viral pathogens. The filly was treated for pyrexia with nonsteroidal anti-inflammatory agents. She was found dead in her stall the morning of presentation.On necropsy, the mucous membranes were severely congested and cyanotic. There were approximately 5 liters of clear yellow-orange watery fluid in the thoracic cavity (Fig. 1). Similar fluid infiltrated and expanded the interlobular septa and visceral pleura of the lungs, which were very heavy. The trachea contained abundant froth, which extended to bronchi and bronchioli in association with fibrin. The lymphoid follicles around the epiglottis were prominent. The meningeal blood vessels were moderately hyperemi...

Respiratory and neurological disease in rabbits experimentally infected with equid herpesvirus 1

“…EHV-1 initially replicates in the epithelial cells of the nasal mucosa of horses and then spreads to the upper and lower respiratory tract causing severe pulmonary edema and hemorrhage, associated with vasculitis [26]. Similarly to horses, six rabbits of the present study (#2, #5, #3F, #4F, #6F and #10F) developed lethal acute viral bronchointersticial pneumonia with vasculitis, thrombosis and diffuse alveolar edema.…”

A review of traditional and contemporary assays for direct and indirect detection of Equid herpesvirus 1 in clinical samples

“…Portions of these tissues can also be collected in 10% buffered formalin along with spinal cord and brain from suspect cases of EHM for histologic (hematoxylin and eosin) and immunohistochemical (IHC) examinations. 15 Samples also can be collected in glutaraldehyde for electron microscopic examination.…”

“…IHC staining methods to detect viral antigen in paraffin-embedded tissues of aborted equine fetuses or neurologic cases have been described. 14,15,23 IHC staining along with hematoxylin and eosin examination is particularly useful for the simultaneous evaluation of lesions and identification of the infectious agent in infected tissues. Similarly, FAT can be used to demonstrate viral antigen in frozen tissue sections.…”

Pharmacokinetics of acyclovir in adult horses

“…EHM differs from herpes virus associated neurologic disorders in other species in that there is no clear evidence of direct neuronal invasion or damage because of the virus itself in EHM. Other forms of disease in the horse attributable to EHV‐1 infection include respiratory disease, respiratory vasculotropic disease, abortion, and neonatal infections which are almost uniformly fatal 8–10 …”