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How do myiasis-causing flies find their hosts?

Traumatic myiasis is a debilitating and sometimes fatal condition of humans and animals caused by the feeding and development of fly larvae on the host's dead or living tissues, usually at the skin surface or in body orifices.

Screwworm maggots and adult flies showing various stages of their life cycle

A critical phase in the life cycle of these species is host location. This is usually down to the adult female fly, 'gravid' with eggs or young larvae ready to be laid. One question being addressed by the Veterinary Research Programme (Department of Entomology) within the Biomedical Sciences Theme is how these flies locate their hosts.

Knowledge of this can help in designing new ways of controlling these flies, by interfering with their natural host location.

Screwworms on a sheep's hoof.

There has been much research on how biting flies, such as mosquitoes, tsetse flies and horse flies, find their hosts. However, the same behaviour by myiasis-causing flies has been little studied. Within the group of flies causing traumatic myiasis, there is a fascinating evolutionary trend - from species that feed only on dead vertebrate tissues, such as carrion, to species that are obligate parasites, feeding only on living tissues (Below you can view two images of an elephant carcass at the start of and seven days after infestation by blowflies that usually breed in carrion but that can cause myiasis).

A scanning electron micrograph of a screwworm's mouthparts.

Such trends are evident in several genera of blowflies (Calliphoridae) and fleshflies (Sarcophagidae) and the Veterinary Research Programme is interested in elucidating the adaptations in behaviour and morphology that followed the change from non-parasitic to parasitic mode of life. Work on this problem has included studies on screwworm flies in Mexico and on a variety of species in Europe.

Elephant carcass at the start of infestation by blowflies.
The same elephant carcass seven days after infestation.

For further information contact:

Dr Martin Hall
Medical and Veterinary Division
The Natural History Museum
Cromwell Road
London SW7 5BD UK
Tel: +44 (0)20 7938 9451 Fax: +44 (0)20 7938 8937/9395
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last updated: 31-Jan-2003