Immunohistochemical identification and pathologic findings in natural cases of equine abortion caused by leptospiral infection.
Authors: Szeredi L, Haake D A
Journal: Veterinary pathology
Summary
# Editorial Summary: Leptospiral Abortion in Horses – Improving Diagnostic Accuracy Leptospiral infection remains a sporadic but significant cause of equine abortion, yet diagnosis has historically relied on silver staining and serology—methods with notable limitations in sensitivity and specificity. Szeredi and Haake examined 96 aborted fetuses from 57 farms using immunohistochemistry (IHC), silver staining, and microscopic agglutination testing to evaluate whether IHC could improve diagnostic reliability. IHC proved substantially more sensitive than silver staining (90.5% versus 38.1% of positive tissue samples) and more specific than serological testing, with both multivalent whole-cell and LipL32-specific antisera yielding consistent results; the technique's key advantage lies in detecting leptospiral antigen regardless of bacterial morphology, capturing degenerate organisms that silver stains may miss. Although leptospirosis was confirmed in only 3.1% of the cohort, practitioners investigating abortion should recognise that IHC offers superior diagnostic accuracy when leptospiral infection is suspected, whilst a novel finding of hepatic nodular necrosis may provide additional gross pathological clues during fetal necropsy. For stud operations experiencing recurrent abortion losses, partnering with a laboratory offering IHC analysis alongside traditional methods will substantially improve diagnostic yield and inform appropriate mare management and biosecurity decisions.
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Practical Takeaways
- •If investigating equine abortion on your farm, request immunohistochemistry testing rather than silver staining—it's significantly more sensitive (90% vs 38%) at detecting leptospiral infection
- •Leptospiral abortion, while uncommon (3% of cases), occurs across multiple farms and should remain on your diagnostic differential for reproductive losses
- •Serology alone is insufficient for diagnosis; pathologic examination with appropriate staining techniques is essential for confirming leptospiral-induced abortion
Key Findings
- •Leptospiral infection identified in 3.1% of aborted equine fetuses (3/96) from 5.3% of farms (3/57)
- •Immunohistochemistry (IHC) demonstrated 90.5% sensitivity compared to 38.1% for silver staining in detecting leptospiral antigen
- •IHC was superior to both silver staining and serology (microscopic agglutination test) for diagnostic specificity
- •A novel macroscopic finding of pinpoint grayish-white hepatic nodules with histologic correlate of necrosis was identified in one confirmed case