Association between forage mycotoxins and liver disease in horses

Background: Outbreaks of liver disease in horses are common but the etiology of most remains unknown. Forage mycotoxins have been suspected to be a cause.

Objectives: To examine the association between outbreaks of liver disease and the presence of mycotoxins in forage stored on the same premises.

Animals: Premises were identified where ≥4 horses were contemporaneously affected by liver disease, and a control group was formed from premises where ≥4 horses had been examined and found to have no evidence of liver disease.

Methods: Forage was collected from 29 case and 12 control premises. The forage was analyzed for mycotoxin content using a liquid chromatography/mass spectrometry method, targeting 54 mycotoxins. The presence and distribution of mycotoxins between case and control samples was compared.

Results: Mycotoxins were found in 23/29 (79%) case samples and 10/12 (83%) control samples (P > .99; relative risk, 0.93; 95% confidence interval [CI], 0.64-1.75). Median (interquartile range [IQR]) total mycotoxin concentration was similar in case and control samples (85.8 μg/kg [1.6-268] vs. 315 μg/kg [6.3-860]; P = .16). Ten mycotoxins were found exclusively in case premises comprising fumonisin B1, 15-acetyldeoxynivalenol, deoxynivalenol, zearalenone, aflatoxins B1 and G1, methylergonovine, nivalenol, verruculogen, and wortmannin. The median (IQR) concentration of fumonisin B1 was significantly higher in case versus control samples (0 μg/kg [0-81.7] vs. 0 μg/kg [0-0]; P = .04).

Conclusions and clinical importance: Several mycotoxins with known hepatotoxic potential were found, alone or in combination, exclusively at case premises, consistent with the hypothesis that forage-associated mycotoxicosis may be a cause of outbreaks of liver disease in horses in the United Kingdom.