Introduction
This topic covers the family Muscidae (the house flies and their relatives) and the tsetse fly Glossina palpalis. Both belong to the order Diptera, the true flies. The house flies are mainly mechanical carriers of pathogens and cause myiasis, while the tsetse fly is a biological vector of African trypanosomiasis (sleeping sickness).
General features of the Diptera and the family Muscidae
Diptera have one pair of functional wings; the hind wings are reduced to small balancing organs called halteres. The larvae are usually legless maggots, and the adults feed on liquids. Muscidae are cyclorrhaphous flies with a mostly medium-sized body. The adults are often hairy and may be found on food, faeces and wounds.
- Adult flies carry bacteria, viruses and protozoan cysts on their hairs and legs and in their gut.
- Larvae develop in decaying organic matter, faeces, carrion or living tissue, depending on the species.
Important Muscidae of medical interest
The house fly (Musca domestica) is the best-known species. It is a mechanical vector: it does not multiply the pathogen but transports it from faeces and garbage to food. It can spread Salmonella, Shigella, enteropathogenic Escherichia coli, Vibrio cholerae and the eggs of intestinal helminths.
The stable fly (Stomoxys calcitrans) is a blood-sucking species that bites the legs of animals and occasionally humans. It can transmit Bacillus anthracis and trypanosomes of domestic animals mechanically.
Myiasis is the infestation of living humans or animals with fly larvae. Facultative and accidental myiasis are caused by Muscidae such as Musca, Fannia and Hydrotaea, which lay eggs on wounds, in the nose, eyes or ears, or in faeces. The larvae feed on the tissue and cause local destruction, pain and secondary infection.