Hydrotaea irritans

H.irritans female - Copyright Alan Hadley

H.irritans male - Copyright Alan Hadley

• Also known as the 'head fly'

• Hydrotaea irritans the main species of veterinary importance

• Mainly a problem of sheep
  • In some areas it is the most numerous fly of cattle and horses

Recognition

• Similar to Musca spp.

• Olive green abdomen

• 4-7mm in length

Life Cycle

• Eggs laid in decaying vegetation, faeces and in carrion (in the summer months)

• Emerging larvae overwinter (diapause) and pupate in spring

• Adult flies emerge in the summer

• One generation per year

Pathogenesis

• Cattle
  • Evidence suggests that they transmit summer mastitis

• Sheep
  • Cause extreme irritation
    • Mouthparts rasp the skin to feed on secretions and exudate
  • Leads to self-inflicted damage
    • E.g. 'Broken Head'
  • Secondary bacterial infection may occur
  • Blowfly strike may follow