Time Course-Dependent Study on Equine Herpes Virus 9-Induced Abortion in Syrian Hamsters.
Authors: Abas Osama, Abdo Walied, Kasem Samy, Alwazzan Abdulatif, Saleh Asmaa G, Saleh Ibrahim G, Fukushi Hideto, Yanai Tokuma, Haridy Mohie
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: EHV-9 Abortion Pathogenesis Across Pregnancy Stages Understanding how equine herpes virus 9 (EHV-9) causes pregnancy loss requires knowledge of the gestational stage at which infection occurs, as placental development fundamentally alters viral pathogenesis and fetal outcomes. Researchers inoculated pregnant Syrian hamsters with EHV-9 at either day 5 (early trimester) or day 10 (late trimester) of gestation, then examined viral distribution, histopathological changes, and fetal viability at multiple timepoints across the pregnancy. Late-trimester infection resulted in significantly higher fetal mortality than early infection, with the virus demonstrating distinct tissue tropism depending on placental maturity: in early pregnancy, the virus localised primarily within decidual leukocytes and was constrained by the developing placental barrier, whereas late-stage infection allowed viral penetration into chorionic villi, trophoblasts, and fetal tissues directly. Both timepoints produced characteristic necrosis of placental structures, though the mechanism differed—early infection damaged the maternal decidua and stromal cells, whilst late infection targeted the chorionic villi and trophospongium layer that had by then become the primary fetal-maternal interface. For equine practitioners, these findings suggest that the timing of EHV-9 exposure during pregnancy significantly influences abortion risk and tissue involvement, with implications for understanding why mares infected late in gestation experience more severe fetal loss and informing surveillance and management strategies accordingly.
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Practical Takeaways
- •This study in Syrian hamsters provides foundational understanding of EHV-9 pathogenesis relevant to equine reproductive medicine, though direct clinical application requires verification in equine models
- •The timing of infection during pregnancy significantly affects abortion risk and pathological mechanisms, suggesting that pregnancy stage is a critical determinant of disease severity
- •Understanding that placental barrier function develops during gestation helps explain why late-trimester infections may carry higher risk for fetal compromise in pregnant animals
Key Findings
- •Late trimester EHV-9 inoculation (day 10) resulted in markedly increased fetal mortality compared to early trimester inoculation (day 5)
- •Early trimester infection caused coagulative necrosis in maternal spaces and stromal decidual cells, with viral localization in mononuclear leukocytes
- •Late trimester infection demonstrated degenerative changes in chorionic villi and trophospongium with viral antigen in multiple fetal tissue types
- •EHV-9-induced abortion primarily occurs through necrosis of chorionic villi; the virus cannot penetrate the capsular placenta in early trimester but can in developed decidual placentation