Metabolomic and systematic biochemical analysis of sheep infected with Fasciola hepatica

Fasciolosis is a neglected zoonotic parasitic disease caused by liver flukes, Fasciola hepatica. F. hepatica is harmful to livestock and human health. However, changes in host metabolism caused by F. hepatica infection are unclear. An artificial sheep model was established as follows. The sheep in the infection group were fed with 220 metacercariae obtained by incubating F. hepatica miracidia with the intermediate host snail (Galba pervia). Thereafter, serum and blood were collected from these sheep periodically. Changes in 31 biochemical parameters were systematically tested over different periods of infection. Metabolomic analysis was performed based on liquid chromatography/mass spectrometry (LC-MS) technology using a UHPLC system. Differentially expressed metabolites were analyzed for biomarkers, and changes in the metabolic pathways of the host were evaluated. Ten biochemical parameters (TP, ALB, GLB, DBIL, IBIL, GGT, LDH, CHOL, HDL-C, and BUN) showed significant dynamic changes during the study period. For metabolomic analysis: 13, 27, and 82 differential metabolites (ESI+ mode) and 0, 37, and 83 differential metabolites (ESI- mode) were found on 7, 56, and 98 dpi, respectively. The number of different metabolic pathways increased with disease development. Five metabolites had the highest area under the curve (AUC) value as joint diagnostic factors, indicating their potential use as biomarkers for diagnosing F. hepatica infection. This study establishes the F. hepatica life cycle in an artificial model of sheep infected with F. hepatica to identify changes in metabolic pathways in the host due to infection. Biochemical parameters and metabolomic analysis revealed that not only the biomarkers screened by differentially expressed metabolites have the potential to diagnose F. hepatica infection in sheep, but the differential pathways and biochemical parameters also explain the metabolic pathway changes in the sheep infected with F. hepatica. F. hepatica absorbs the nutrients of the host and destroys the essential metabolic pathways of the host. This result suggests that animal metabolism can be altered in the host as a response to parasitic infections such as F. hepatica. In addition, this finding will provide the basis for studying the pathogenic mechanisms and biomarkers for F. hepatica infection.