In recent years a high number of new viral species have been identified using various molecular techniques that do not depend on the in vitro culture of the agents. A high per cent age of the new viruses may be refractory to efforts to establish an in vitro culture system.  Currently in the equine, there are at least 4 viruses that can establish a chronic and/or persistent infection. Three (NPHV, TDAV, and EqPeg) are in the family Flaviviridae, genus Hepacivirus which also contains the human hepatitis C virus. The fourth virus (EqPV) is in the family Parvoviridae and is yet unclassified as to genus. 

All four of the viruses have been linked to liver disease in horses either by their association with hepatitis C or by preliminary findings in clinically ill horses. The difficulty in establishing causality is that 5-15% of normal horses may be chronically infected. At present, we know very little about the natural spread of these agents, but we do know that biological materials used in the equine industry are contaminated with these viruses, especially pooled plasma and serum products.

The Animal Health Diagnostic Center has developed a panel of PCR tests for the detection of these viruses. At present, we consider these tests as for “research and informational” purposes only as the complete validation of the tests has not been done mainly because of inadequate sequence data available to properly assess the universality of the PCR primers. We will provide testing services to practitioners who wish to explore the clinical relevance of these agents and to providers of equine biologicals who wish to eliminate chronic shedding animals from their production units. The routine sample for PCR testing is a serum sample. If horses are showing signs of liver disease, a biopsy specimen would also be appropriate.

If you wish to assist in helping to define the clinical relevance of these agents, we have two projects that need funding in order to continue to develop materials for enhanced capability to define the pathogenesis of these viruses.  Simply click on the ”Giving” tab on the main webpage and read about the two projects associated with the Equine “Hepatitis” program.