What Do We Know About Hepatitis Viruses in Horses?

Area of Science:

• Veterinary Virology
• Equine Hepatology
• Molecular Diagnostics

Background:

• Theiler disease, a severe liver condition in horses, has long been suspected to be viral.
• Previous research identified several viruses, but their roles in equine hepatitis remain unclear.
• Distinguishing between pathogenic and non-pathogenic viral agents is crucial for diagnosis and treatment.

Purpose of the Study:

• To investigate the viral etiology of Theiler disease in horses.
• To determine the pathogenic potential of suspected viruses, including equine parvovirus-hepatitis (EqPV-H) and nonprimate hepacivirus (NPHV).
• To clarify the role of different viruses in equine liver disease.

Main Methods:

• Review of existing literature on equine hepatitis and associated viruses.
• Experimental studies on the pathogenicity of EqPV-H and NPHV in equine models.
• Clinical case analysis correlating viral detection with liver pathology.

Main Results:

• Equine pegivirus and Theiler disease-associated virus were found to be non-hepatotropic and non-pathogenic.
• Nonprimate hepacivirus (NPHV) caused subclinical disease in experimental settings and was linked to some clinical hepatitis cases.
• Equine parvovirus-hepatitis (EqPV-H) experimentally induced liver disease and was detected in most Theiler disease cases, indicating high clinical significance.

Conclusions:

• Equine parvovirus-hepatitis (EqPV-H) is strongly implicated as a causative agent of Theiler disease in horses.
• The clinical significance of nonprimate hepacivirus (NPHV) in equine hepatitis remains uncertain.
• Further research is needed to fully elucidate the complex viral landscape of equine liver disease.