Authors

Discussion

The Differential outcomes of Fasciola hepatica (Fh) infection on the liver pathology and blood chemistry in naturally infected ruminants are well known. In addition, hepatic and peritoneal changes and immune response have been recorded in vaccination trials following artificial challenge infections. However, the variety and range of effects of fascioliosis on individuals is not well characterised.  This study aimed to measure this variation using commercially reared Texel X lambs given a defined challenge of F. hepatica isolate.  In total, 15 female and 2 male (castrated) lambs having no previous exposure to liver fluke, were each challenged with 200 metacercariae from a confirmed TCBZ susceptible F. hepatica isolate. During the 12 weeks of infection animals maintained reasonable body condition and showed no clinical signs. At post mortem, data was collected for body weights, liver weights, numbers of adult fluke, and liver condition was scored. Images of liver pathology were also recorded. Blood samples were collected for liver enzyme analysis and antibody response testing. Results demonstrated an average infection rate of 51% (range 19.5 to 83.5%) with high levels of liver enzymes; GGT up to 13 times the normal range and GLDH up to 40 times the normal range. Liver morphology scores revealed moderate adverse changes in 3 of the animals, the remaining 14 exhibiting mild changes. Thus, the study confirmed variation in individual host responses in a challenge that could lead to chronic F. hepatica infection, with no apparent correlation between, or trends in, the levels of fluke infection and pathological, biochemical or antibody responses. Future studies will repeat the experiment with significantly lower F. hepatica infection levels in order to delineate individual response profiles.