Age-associated responses in susceptible and resistant rats to infection with Fasciola hepatica

Rajasekariah G. R. and Howell M. J. 1981. Age-associated responses in susceptible and resistant rats to infection with Fasciola hepatica. International Journal for Parasitology11: 59–65. Groups of susceptible (5-week-old) and age resistant (25-week-old) outbred male Wistar rats were infected with metacercariae of Fasciola hepatica and the establishment of the parasite was assessed in terms of worm reocvery, and haematological, histopathological and immunological criteria, 2, 4, 6 and 8 weeks after infection. Apart from 2 weeks after infection, there was a significant difference between groups in the recovery of F. hepatica, with resistant rats infected with consistently fewer parasites than susceptible animals. The juvenile worms which invaded the livers of resistant rats elicited a number of host reactions, marked by an intensive cellular infiltration into migratory tracks of the parasite, heavy deposition of fibrous tissue in the liver parenchyma and a rapid antibody response. These responses were not as striking in susceptible animals even though more worms were present. The ability of resistant rats to mount an enhanced response seems related to the maturation of their haemopoietic system.