Ovine gammaherpesvirus 2 vertical infections in sheep

Ovine gammaherpesvirus 2 (OvGHV2) is a Macavirus that causes malignant catarrhal fever (MCF). The Macaviruses inducing MCF share the 15A antigenic epitope and form the MCF virus (MCFV) complex. While transplacental OvGHV2 infections in ruminants are rarely reported, vertical infections in sheep are undocumented. This study presents evidence of transplacental infections in the sheep and support the possible role of Macavirus to induce reproductive infections. A 6-year-old, pregnant, Santa Inês ewe with a history of twin pregnancies died spontaneously due to the metabolic complications of pregnancy toxemia. Post-mortem evaluation revealed that the pregnant ewe was carrying two fetuses. Organs from the ewe and fetuses were analysed using a 15A-based immunohistochemical (IHC) assay to detect MCFV tissue antigens and PCR to amplify the OvGHV2 tegument protein gene. Significant pathological alterations observed were brain edema and hepatocellular degeneration in the ewe, and brain edema in both fetuses. The 15A-IHC assay detected MCFV antigens in tissues of various organs of the ewe and Fetus #2. OvGHV2 DNA was amplified from multiple organs of the sheep, the cerebrum of Fetus #1, and the liver of Fetus #2. These findings confirmed that the MCFV antigens identified by IHC were those of OvGHV2, demonstrating that both fetuses were infected by this Macavirus. This report likely represents the first description of OvGHV2-related transplacental infections in the sheep. These results further confirm the involvement of Macavirus in reproductive infections of ruminants and the effectiveness of the 15A IHC assay in detecting MCFV antigens within tissues of fetal organs.