Two cases of equine abortion caused by Rhodococcus equi.

The research highlighted two instances of horse abortions, caused by an infection from a bacterium known as Rhodococcus equi. The bacteria were identified from various organs of the aborted foetuses and the resulting lesions and impacts are similar to those observed in foals.

Study Context and Methodology

• The study seeks to understand the cause of abortion in two equine fetuses, both of which were between seven and eight months gestation, from two different farms. Researchers isolated the bacterium Rhodococcus equi from the lung, liver, spleen, and stomach content of these fetuses.
• The detection method involved bacteriology and immunohistochemistry, which is a process for identifying cells based on the presence of specific antigens. In this case, the research team was looking for the presence of R. equi and VapA, a known virulence factor of R. equi.

Findings

• The research found that lesions, or areas of damaged tissue, in the fetuses showed signs of pyogranulomatous pneumonia. This is an inflammatory lung disease usually associated with bacterial infections.
• Additionally, these lesions contained numerous Gram-positive coccobacilli, a type of microscopic bacteria, within various cells. Also found was enhanced extramedullary hematopoiesis with megakaryocytosis within the liver and spleen, which indicates an increased production of blood cells outside the bone marrow, an abnormality frequently connected with severe illness.
• Both R. equi and VapA were detected within the lungs of the fetuses, and the distribution of these bacteria corresponded with the damaged tissue areas. Essentially, the lesions and the bacteria were found in the same places.

Interpretation and Implications

• The study deduced that the observed pathology in the fetuses is consistent with R. equi infection and similar to symptoms observed in foals.
• Researchers postulate that the fetuses may have contracted the infection from the placenta either through normal breathing movements or by swallowing amniotic fluid contaminated with R. equi.
• This research contributes to the understanding of equine fetuses’ pathogen exposure and the potential for resulting complications, including abortion, providing valuable information for veterinary science and animal health management.