Faecal egg count patterns. Mean faecal egg count patterns over time (McMaster method), showing a significant difference (p = 0.002) in egg shedding patterns between isolates (groups) A, B and C from 1-45 d.p.i. However, there was no significant difference (p = 0.34) when comparing the egg shedding levels of the three groups before treatment, 1-35 d.p.i. Group A was infected with a propagated IVM-susceptible laboratory isolate and groups B and C with two different Swedish field isolates showing phenotypic clinical IVM resistance in field trials. All calves were treated with injectable IVM at 35 d.p.i.