Chrysomya bezziana

Screw Worm Myiasis

Screw worm larvae - John Kucharski - Wikimedia Commons

• C. bezziana cause myiasis in both animals and humans

• Located mainly in tropical regions

• Larvae are obligate parasites

Recognition

• Similar to Calliphora spp.
  • Iridescent
  • Clear wings
  • Blue abdomen

• Longitudinal stripes on thorax

• Larvae have bands of spines
  • Look like screws

Life cycle

• Eggs laid in wounds or body cavities

• Larvae feed as colonies

• Larvae drop to the ground to pupate

Pathogenesis

• Spiracles are exposed as larvae feed which expands the wound
  • Creates a foul smelling lesion

• Cause irritation and pyrexia

Control

• In the USA
  • Mass eradication through the release of sterile males
  • Currently only persists where flies have migrated across the Mexican border

• In Africa
  • Introduced into Libya through the importation of infested livestock
  • Sterile males released
  • Eradication occurred in 1991