Prevalence of liver fluke infection in Irish horses and assessment of a serological test for diagnosis of equine fasciolosis

Summary Background There is little information on the prevalence of Fasciola hepatica infection in the horse population in Ireland or the potential impact of fluke infection on animal health. Objectives To investigate F. hepatica infection in the Irish horse population and to assess the diagnostic potential of an indirect enzyme‐linked immunosorbent assay (ELISA) based on the F. hepatica recombinant cathepsin L1 (CL1) antigen. Study design Cross‐sectional abattoir survey of horses for liver fluke status. Methods Animals (n = 200) were examined at an abattoir between May 2013 and April 2014. Horses were graded ante mortem for body condition score. Blood and faeces were collected and livers were examined post mortem by gross morphology. A cohort (n = 35) of livers were also examined histologically. Haematology and blood biochemistry, including serum liver enzyme activities, were measured and faeces were sedimented for egg counts. Serum was assayed by indirect ELISA using a recombinant CL1. Results The prevalence of liver fluke infection was 9.5%. There was no correlation between liver fluke status and time of year, breed classification, age group, sex, body condition score, ante mortem assessment, strongyle infection status, serum liver enzyme activities or CL1 concentration. A comparison of the CL1 ELISA in horse sera compared with a reference standard diagnosis showed high specificity of 95.6% (95% confidence interval [CI] 91.5–98.0%), but low sensitivity of 42.1% (95% CI 20.2–66.5%). Main limitations This study is limited by its nature as an abattoir study, the relatively small number of animals examined (n = 200), and the absence of a known negative group of horses. Conclusions Blood biomarkers are not good indicators of liver fluke infection and the CL1 ELISA is not a sensitive tool for diagnosis of fluke infection in the horse. The prevalence of F. hepatica in horses indicates that further research is required to assess the potential impact of liver fluke on equine liver health.