A case of equine abortion caused by Encephalitozoon sp.

This research discusses the case of a horse’s pregnancy prematurely terminated due to an infection by Encephalitozoon, a genus of Microsporidia. This is the first reported incident of such an occurrence in Europe, and it emphasizes the importance of considering microsporidia in the diagnosis of abnormal cells in horses’ reproductive systems.

Case Presentation

• The situation involves a Lippizan mare that had a premature termination of pregnancy, also known as an abortion, of a male fetus. This happened a short time before the anticipated birthing date, and interestingly, no outward signs of illness were exhibited by the mare.

Findings

• Several irregularities were spotted via examination of the foal and the mare’s endometrial tissue. These include inflammation and tissue death in multiple areas, as well as a significant increase in the size of cells in the lining of the womb.
• Nucleated organisms were observed within the cellular structure of the lining, either in collections or as single entities. These were particularly common in areas displaying inflammation and necrosis, and even seen outside of cells.

Identification

• Different staining methods were used to help characterize these organisms. They returned positive results for a Gram stain, haematoxylin and eosin (HE), periodic acid-Schiff (PAS), and Giemsa dye methods, and a weak positive for Warthin-Starry silver stain. However, they were negative with Gömöri’s methenamine-silver stain.
• Through detailed examination involving ultrastructural and immunohistochemical methods, these organisms were confirmed as microsporidia belonging to the genus Encephalitozoon. However, it’s noted that none were found in the organs of the fetus.

Implications

• This is the first observed case in Europe of an equine abortion attributed to a microsporidian infection, specific to Encephalitozoon.
• While abortions due to this infection are uncommon, this discovery underscores the importance of including microsporidia in any differential diagnosis when similar intracellular organisms are identified within the reproductive tissue of horses.