title: An analysis of variations in the age structure of Fasciola hepatica populations in sheep.
abstract: The processes which govern the age structure of Fasciola hepatica populations in sheep were investigated by means of a simple mathematical model. The mortality of the metacercariae on the pasture was shown to be a factor of major importance. The mortality rate depends on the micro-climate that prevails at the pasture surface, and thus the age distribution curve of a population of flukes is also determined in part by the weather. This has important implications for the chemotherapy of fascioliasis: flukicides are not equally effective over the whole range of age-classes of parasite and so the factors which govern the age distribution curve of the parasite population within individual hosts ultimately determine the efficiency of chemotherapy.
mesh_terms: D000375:Aging; D000818:Animals; D005210:Fasciola hepatica / Q000254:growth & development*; D005211:Fascioliasis / Q000188:drug therapy / Q000469:parasitology / Q000662:veterinary*; D008433:Mathematics; D008954:Models, Biological; D012621:Seasons; D012756:Sheep; D012757:Sheep Diseases / Q000188:drug therapy / Q000469:parasitology*; D014887:Weather