Myiasis - pigs

Myiasis is the infestation of living vertebrates with the larvae of flies, the species of which vary with location around the world.  The term myiasis is usually applied to those genera of flies that cause problems in the skin and sub-cutaneous tissues of people, domestic animals and wildlife, but sometimes invade deeper tissues.  The larvae of other genera (e.g. Gasterophilus of horses and Hypoderma of cattle) migrate through the tissues of the host, but are not usually associated with skin lesions.  The larvae causing myiasis must feed on the tissues of affected animals, sometimes causing serious clinical problems, and even death.  The animals develop myiasis when the adult female flies are attracted to a wound or to a hair coat contaminated with urine and/or faeces, where they lay eggs (or larvae - Wohlfahrtia species).  On the animals, the eggs hatch and develop through three larval stages.  The third-stage larvae, whose feeding activities can seriously damage the host, drop to the ground, where they form pupae in which the immature adult flies develop before hatching.  Particularly susceptible to myiasis are animals and people who are attractive to the adult flies and are unable for some reason to fend them off or remove the eggs and larvae.

The flies associated with myiasis can be classified into two groups: 1) obligate - those that must develop on live hosts (e.g. Wohlfahrtia vigil - flesh flies); and 2) facultative - those that can develop in either live or dead hosts or in organic matter.  Genera causing facultative myiasis are further classified as primary, which can initiate myiasis (e.g. Lucilia species - blow flies/greenbottles), or as primary and secondary (e.g. Lucilia species, Calliphora species - blow flies/bluebottles, Phormia species - blow flies/blackbottles, and Wohlfahrtia species), which require obligate or primary genera to initiate the infestation.

Myiasis in Pigs