The characteristic seasonal pattern of strike observed in the field is also accurately predicted by the model simulations
(Fig. 1). Strikes are seen first in early Spring, and during Spring and early Summer ewes are the most heavily
struck age-class because their long fleeces can become wet and soiled by faeces, promoting high blowfly egg
and larval survival. However, following shearing ewe susceptibility is reduced substantially. Lambs initially have
short fleeces and low susceptibility, but after weaning in summer, a combination of diarrhoea caused by
temperature-dependent GI infection and a growing fleece leads to faecal soiling and rapidly increases their susceptibility
to strike. Lamb strikes therefore increase in incidence from mid-summer onwards. However, the incidence of
ewe strikes can increase again towards the end of the season if the autumn is warm and wet, because of the growing
fleece, which increases ewe susceptibility (French et al.,1994a).