Fasciola hepatica and Fasciola gigantica: comparison of cellular response to experimental infection in sheep

Cellular responses to Fasciola gigantica and to Fasciola hepatica infection in sheep were compared. Eosinophil numbers increased more quickly and strongly in F. gigantica-infected sheep than in F. hepatica-infected sheep. In both groups, peripheral blood mononuclear cell (PBMC) proliferation in response to the parasitic excretory-secretory products (ESP) showed similar kinetics. Interferon-gamma (IFN-gamma) production by ESP-stimulated PBMC was early and showed similar kinetics in both groups. Interleukin-10 (IL-10) production by FhESP-stimulated PBMC was very high throughout infection even at 0 weeks post-infection (WPI) in F. hepatica-infected sheep, while in F. gigantica-infected sheep, IL-10 production by FgESP-stimulated PBMC increased between 1 and 4 WPI. IL-10 production in F. gigantica-infected sheep was significantly lower than in F. hepatica-infected sheep during infection. The lower susceptibility to F. gigantica infection in sheep could be explained by the more intense cellular response induced by the parasite and the weaker capacity of F. gigantica to evade the immune response.