Two cases of equine abortion caused by Rhodococcus equi.
Authors: Szeredi L, Molnár T, Glávits R, Takai S, Makrai L, Dénes B, Del Piero F
Journal: Veterinary pathology
Summary
# Editorial Summary: Rhodococcus equi-Associated Equine Abortion Rhodococcus equi, a well-recognised pathogen in neonatal foals, was confirmed as the causative agent in two separate cases of mid-to-late gestation abortion (at 7 and 8 months), with the bacterium isolated from multiple fetal organs including lungs, liver, spleen and stomach contents. Pathological examination revealed characteristic pyogranulomatous pneumonia with organisms identified within macrophages and giant cells, alongside marked extramedullary haematopoiesis in hepatic and splenic tissues—lesions virtually identical to those seen in clinically affected foals. The researchers employed both conventional bacteriology and immunohistochemistry targeting the VapA virulence factor to confirm diagnosis and map bacterial distribution, which correlated precisely with tissue damage patterns. The findings suggest intrauterine infection occurs through aspiration or ingestion of contaminated amniotic fluid across an infected placenta, implying that placental colonisation represents a critical pathogenic pathway that has received limited attention in reproductive disease literature. For equine practitioners, this case series expands awareness that R. equi should feature in diagnostic considerations for unexplained mid-to-late gestation losses, and highlights the importance of detailed necropsy with immunohistochemical confirmation, particularly where farm biosecurity or neonatal foal disease history suggests environmental contamination.
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Practical Takeaways
- •Rhodococcus equi should be considered in the differential diagnosis for equine abortion, particularly in cases with pyogranulomatous lung lesions on necropsy
- •Environmental contamination with R. equi poses intrauterine infection risk to pregnant mares; biosecurity and farm management practices warrant attention on farms with abortion cases
- •Immunohistochemistry detection of VapA can assist in confirming R. equi diagnosis in aborted fetuses when bacteriology results are pending
Key Findings
- •Rhodococcus equi was isolated from lung, liver, spleen, and stomach content of two aborted equine fetuses at 7 and 8 months gestation
- •Fetal lesions included diffuse pyogranulomatous pneumonia with Gram-positive coccobacilli within macrophages and Langhans giant cells
- •VapA virulence factor was detected via immunohistochemistry in lung tissue of both fetuses, with distribution correlating to lesion sites
- •Fetuses likely contracted infection transplacentally through normal breathing movements or aspiration of contaminated amniotic fluid