topathological changes observed in the liver of buffaloes experimentally infected with *F. gigantica*GroupDpiNo. of animalsInflammatory infiltrationRBCsEosinophilsNeutrophilsFibroblastsLymphocytesMonocytesI05--------------II35+----+--+--III105++++--+--IV285++++--++V425+++++++VI705+++++++VII984+++++++ Fig. 1Histopathological characteristics of the livers of buffaloes infected with *Fasciola gigantica*. **a** At 3 dpi, there was local hyperemia associated with mild filtration of lymphocytes and neutrophils. **b** At 10 dpi, there was scattered vacuolation of hepatocytes, consistent with fat, along with mild to moderate focal necrosis. **c** At 28 dpi, diffuse intravascular coagulation, severe infiltration of inflammatory cells mainly neutrophils and lymphocytes, and granular degeneration of the cytoplasm were observed. **d** At 42 dpi, moderate to severe multifocal hemorrhages and necrosis, infiltration of eosinophils, RBCs and monocytes, and accumulation of fibroblasts were detected. **e** At 70 dpi, there were mild to moderate multifocal bile duct hyperplasia and focal coagulative necrosis associated with collagen deposition. **f** At 98 dpi, severe periportal fibrosis associated with multifocal inflammatory infiltrate, cellular debris, moderate multifocal hemorrhages, and granulomas with necrotic centres were detected. **g** Liver tissue from uninfected animal showed normal histological architecture of the hepatic tissue. **h** Adult flukes in the intrahepatic bile duct, along with epithelial hyperplasia of the duct. In all figures, tissue sections were stained with H&E and arrows point at the corresponding morphological features described above. *Scale-bars*: **a-g**, 50 μm; **h**, 100 μm

Gene expression of cytokines {#Sec12}
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To determine how immune response changed over the course of infection, gene expression of nine cytokines was assessed in the liver tissue of 29 infected buffaloes and five uninfected buffaloes using qRT-PCR. RNA from one animal from group VII did not pass