Blowflies as pests

Nature

Blowflies are large flies of the family Calliphoridae. Although the larvae of blowflies usually feed on decaying meat, they sometimes infest open wounds, eating healthy tissue. They may live within the flesh of man and his domestic animals, forming tumours.

Incidence

The most dangerous species are the screw worms, which attack both man and livestock, especially sheep and goats. They occur in tropical regions and the southern USA. Several species of blowfly attack, and will kill, livestock in Australia, where these is a $150 million-a-year blowfly strike problem in sheep. The Old World screw worm is widely distributed in the Pacific regions, Australia and Asia, occurring in enormous numbers, breeding in decaying vegetation, manure, human excrement and carcasses. It is a most important vector of dysentery, jaundice and anthrax.

Counter-claim

Blowfly maggots were introduced into battlefield wounds by military surgeons from the USA Civil War until the 1930's as a means of cleaning wounds. Many thousands of soldiers's lives and maybe untold thousands of non-military lives were saved using this procedure. Blowfly maggots have in their guts large populations of benign bacteria which exude two powerful bactericides, phenylacetic acid and phenylacetaldehyde, to which they are resistant. In the environment of the open wound these substances are not stable enough to be protective. The maggots eating debris and infectious microbes allows the benign bacteria to act as a filter, resulting in bacteriological cleanliness, rapid healing and removal of unnecessary scar tissue.