Equine liver disease in the field. Part 2: causes and management

The approach to equine liver disease was explored in part 1 of this series (Tallon and McGovern, 2020). This article discusses selected causes of liver disease in more detail, providing updates from recent literature. These focus on toxic and infectious aetiologies, which typically cause subclinical disease at a herd level. Identification of a specific cause is not possible in many clinical cases and, instead, treatment is discussed based on clinical findings and biopsy results. Dietary modifications and supplementation for horses with liver disease is also reviewed. A more complete summary of causes of liver disease is illustrated in Table 1 but discussion of each of these in detail is beyond the scope of this article.

Toxic hepatopathy should be considered if multiple horses on a premises are affected and, if suspected, hay and soil analysis should be performed. Mycotoxins are common in hay and feed. No clear association between aflatoxin contamination of forage with liver disease has been found, but fumonisin B₁, a toxin produced by Fusarium spp., has been shown to cause liver disease (Ross et al, 1993). More recently, the toxin was consistently identified in the forage of horses with liver disease but not in controls (Durham, 2017). Mycotoxin testing kits are commercially available and if contamination is suspected or confirmed, forage should be changed. In-feed mycotoxin adsorbents can also be used. Supplementation with a polymeric glucomannan adsorbent was shown to attenuate increases in gamma glutamyl transferase associated with Fusarium spp. ingestion in one study (Raymond et al, 2003) but further research is currently lacking.