Naturally acquired equine parvovirus-hepatitis is associated with a wide range of hepatic lesions in horses.
Authors: Jager Mason C, Choi Eunju, Tomlinson Joy E, Van de Walle Gerlinde
Journal: Veterinary pathology
Summary
Equine parvovirus-hepatitis (EqPV-H), known primarily as the cause of Theiler's disease, presents a far broader spectrum of hepatic pathology than previously recognised, prompting a reappraisal of its diagnostic significance in equine liver disease. Mason and colleagues examined 98 archived liver samples using in situ hybridisation to detect viral presence and characterise associated histological changes, identifying EqPV-H in nearly half (48%) of diagnostic samples spanning 2007–2022. Individual hepatocyte death, lobular infiltrates, portal infiltrates, and ductular reaction were the predominant findings in infected tissues (85%, 80%, 74%, and 70% respectively), with centrilobular necrosis, portal inflammation, and hepatocyte apoptosis correlating significantly with high viral load. The findings challenge the conventional association between EqPV-H and Theiler's disease alone, suggesting practitioners should consider parvovirus-hepatitis as a differential in varied presentations of equine hepatitis and chronic liver pathology. Whilst equine hepacivirus co-infection was rarely detected, the researchers note that PCR unreliability in fixed tissues may underestimate concurrent viral involvement, emphasising the need for histopathological evaluation alongside molecular diagnostics in suspected hepatic disease.
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Practical Takeaways
- •Nearly half of equine liver disease cases involve EqPV-H, making it a critical consideration in hepatitis diagnostics and case workup
- •High viral load correlates with specific histologic patterns (centrilobular necrosis, portal infiltrates, hepatocyte death), which can help guide clinicians toward suspecting EqPV-H
- •In situ hybridization is more reliable than PCR for detecting EqPV-H in archived tissue samples, so ensure appropriate diagnostic methodology is used
Key Findings
- •EqPV-H was detected in 48% (47/98) of diagnostic liver samples examined
- •Individual hepatocyte death (85%), lobular infiltrates (80%), portal infiltrates (74%), and ductular reaction (70%) were most common histologic features in EqPV-H-positive samples
- •Centrilobular necrosis, portal infiltrate, and individual hepatocyte death were positively associated with high viral load
- •EqPV-H should be considered a differential diagnosis in hepatitis cases beyond Theiler's disease