We are all now recognising that most cases of liver disease that we encounter are part of a wider outbreak amongst herd-mates, even if the others appear externally healthy. This suggests a common toxin or infectious aetiology. It is useful to rule out “old favourites” such as ragwort by biopsy. Fluke is rare and almost impossible to rule out as no antemortem tests are reliable.
Work performed at Liphook over the last few years has identified fumonisin B1 contamination of forage as a possible cause of some outbreaks and international work looking at various causes of viral hepatitis in horses has identified a number of candidates including equine Hepacivirus, equine Pegivirus, Theiler’s disease associated virus and equine Parvovirus.
See Cornell University Laboratory website:
and recent publication describing equine Parvovirus: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5782890/pdf/17-1031.pdf
Continued work at Liphook has identified equine Parvovirus in some horses with liver disease and we hope to offer this, and other, new PCR assays shortly.