Myiasis

Infection by dipterous flies in moist body areas (eg. perineum)
Commonly affects sheep - ovine fleece rot
Grossly:
- Matted hair or wool, may be in wounds
- Multiple holes or ulcers
- Malodour
May result in death due to septicaemia or toxaemia
Cuterebra myiasis
- Caused by Cuterebra sp
- Young animals come into contact with eggs on stones or plants
- Nodules with larvae in subcutis + respiration openings to surface
Hypoderma myiasis
- Caused by Hypoderma lineatum or H. bovis
- Mainly affects cattle
- Skin of legs is penetrated -> migration through oesophagus or vertebral canal to subcutis of back
- Cause subcutaneous nodules with respiration openings
- Larvae in cavity with fibrin and eosinophils surrounded by granulation tissue with eosinophil clusters
Screwworm myiasis
- Occurs in Africa, Asia, Central and South America
- Larvaae are deposited in wounds
- Penetrate and liquify tissue

Pathogenesis

Production losses
- Annoyance
- Bites can lead to secondary infection by myiasis producing flies and other muscid species

Disease transmission
- Pathogenic bacteria and viruses via mechanical transmission
- Helminths can be introduced into the host
  - E.g. Stephanofiliaria a filarial nemadode found in the skin of cattle overseas

Resident fly so easier to control than visiting flies as spends more time in contact with the host