Blowfly strike, known as myiasis, is a common disease in sheep, especially in areas where there are hot and wet conditions. The female flies lay their eggs on the sheep in damp, protected areas soiled with urine and faeces, mainly on the breech. It takes approximately 8 hours to a day for the eggs to hatch, depending on the conditions. This results in sores as the larvae lacerate the skin and this is the primary reason for the early removal of lambs' tails. The larvae then tunnel into the host's tissue causing irritating lesions. After about the second day bacterial infection occurs and if left untreated causes toxemia or septicemia. This leads to anorexia and weakness and if untreated will lead to death. Blowfly strike accounts for over $170 million a year in losses in the Australian sheep industry and so prevention measures such as mulesing are practiced.
German entomologist Fritz Zumpt describes myiasis as "the infestation of live human and vertebrate animals with dipterous larvae, which at least for a period, feed on the host's dead or living tissue, liquid body substances, or ingested food."