Perinatal foal mortality associated with a herpesvirus.

The research article deals with the examination of equine herpesvirus 1 (EHV 1) case which led to high foal mortality in a thoroughbred stud in Australia. This study marks the first report of EHV1 being associated with clinical abortion or neonatal foal mortality in the region.

Case Background

• An outbreak occurred at a thoroughbred stud in the Camden district, where a 3-day-old foal died of severe respiratory distress.
• Following a histopathological exam, the foal was diagnosed with herpesvirus infection. Following this, 90 mares have foaled and 22 foals have died associated with the infection.
• Affected foals were either stillborn, displayed severe respiratory symptoms shortly after birth, or seemed normal at birth but developed respiratory problems 18 to 24 hours later.
• The investigators found that foals exhibited symptoms of elevated temperatures, increased heart rates, and respiratory rates.
• Despite administering antibiotics, diuretics, corticosteroids, oxygen therapy, and assisted positive pressure ventilation, the foals invariably succumbed to the disease.

Clinical Findings

• On inspection of blood samples from a number of foals, the researchers found that they were severely leucopaenic, with total white blood cell counts often less than 3,000/µL. Most of the foals were also neutropaenic, however, lymphopaenia was not a constant feature.
• Autopsy revealed large, firm, oedematous lungs that were a purple color. Other findings included fluid and haemorrhagic striations in the trachea and bronchi, but no excess fluid in the thoracic or abdominal cavities.
• The spleen was slightly enlarged and the lymphoid follicles were often more noticeable. No hepatic lesions were observed.
• On histopathology, lung tissues showed moderate to severe alveolar edema with congestion and collapse. This was associated with a slight to moderate acute necrotising bronchitis with a few to many eosinophilic intranuclear inclusions in the bronchiolar epithelium.

Herpesvirus Isolation and Identification

• Herpesvirus was successfully isolated from 10 foals using a dog kidney cell culture. The virus was subsequently identified via electron microscopy.
• A stillborn foal diagnosed with herpesvirus infection from the Oberon district and two other areas in New South Wales were also reported.

Conclusion and Future Research

• The detection of the disease in three geographical areas in New South Wales suggests that further outbreaks of EHV1-associated foal mortality are to be anticipated.
• A detailed report of the findings will be published in a subsequent issue of the Australian Veterinary Journal.