Histopathological and immunofluorescent studies on transplacental infection in experimentally induced abortion by equine arteritis virus.

The research article is a study on how the equine arteritis virus affects pregnant mares and leads to abortion, as seen through histopathological and immunofluorescent studies.

Experiment Design and Results

• The scientists experimentally infected five mares that were between 6 to 8 months into their pregnancies with the Bucyrus strain of equine arteritis virus (EAV), a virus known to cause disease in horses.
• Outcomes of these infections showed that four out of the five mares had abortions while one mare died.
• Using histopathologic techniques, tissue immunofluorescence, and virus isolation, the researchers studied the pathogenesis of these abortions.

Microscopic Lesions in Maternal Reproductive Organs

• The scientists found common microscopic lesions in the maternal reproductive organs, primarily indicating myometritis, a condition marked by inflammation in the myometrium, the middle layer of the uterus.
• The lesions caused degeneration of the myocytes (muscle cells) and an infiltration of mononuclear cells.
• There was also sporadic degeneration observed in the epithelial cells of the endometrial gland.

Lesions in the Fetal Tissue

• In addition to the lesions found in the maternal reproductive organs, the scientists also documented changes in the fetal tissue.
• They noted atrophy of the lymphoid follicles in the spleen and lymph nodes, with degenerated lymphocytes. Lymphocytes are a type of white blood cell crucial to the immune system.
• The researchers also found that the placentae of the mares were oedematous (swollen with excess fluid) and that degenerated fibroblasts, a type of cell that produces collagen and other fibres, were present in the subvillous layers. The subvillous layer is part of the placenta that attaches to the uterine wall, providing nutrients to the fetus.

Immunofluorescence and Virus Isolation

• Using immunofluorescence, the researchers detected the EAV antigen in the myometrium and the endometrial glands in the mares, in the subvillous layer of the placentae, and in the aborted fetuses.
• The EAV was recovered from the maternal uteri, placentae, and fetuses, with the greatest amounts of the virus being yielded by the placentae.
• These findings clearly demonstrated that transplacental infection of the fetus occurred with the EAV infection.