Home Articles Veterinary medicine Articles Myiasis
Myiasis is an animal or human disease caused
by parasitic dipterous fly larvae feeding on the host's necrotic
or living tissue. Colloquialisms for Myiasis include fly-strike
Zumpt describes myiasis as "the infestation
of live human and vertebrate animals with dipterous larvae,
which at least for a period, feed on the host's dead or living
tissue, liquid body substances, or ingested food."
Two different classifications of myiasis can
The classical classification describes
the myiasis by the infected area of the host. For example
: dermal, sub-dermal, cutaneous, nasopharyngeal, ocular,
intestinal/enteric or urogenital.
Another classification is based on the
relationship between the host and the parasite and provides
insight into the biology of the fly species causing the
myiasis and its likely effect. Thus the myiasis is described
as either obligatory, facultative or accidental.
Flies responsible for Myiasis
There are three main fly families causing
economically important myiasis in livestock and also, occasionally,
The adult flies are not parasitic, however
when they lay their eggs in open wounds and these hatch into
their larval stage (a.k.a. maggots or grubs), the larvae feed
on live and/or necrotic tissue causing myiasis to develop.
Control Methods - Prevention and Treatment
The first control method is preventive and
aims to eradicate the adult flies before they can cause any
damage and is called vector control. The second control method
is the treatment once the infestation is present, and concerns
the infected animals (or humans).
The principal control method of adult populations
of myiasis inducing flies involves insecticide applications
in the environment where the target livestock is kept. organophosphorus
or organochlorine compounds may be used, usually in a spraying
formulation. One alternative prevention methods is the SIT (Sterile
Insect Technique) where a significant number of artificially
reared sterilized (usually through irradiation) male flies are
introduced. The male flies compete with wild bred males for
females in order to copulate and thus cause females to lay batches
of unfertilised eggs which can't develop into the larval stage.
Another prevention method involves removing
the environment most favourable to the flies. One example of
this is the crutching of sheep, which involves the removal of
skin folds between the rear legs, which is a favourable environment
for the larvae.
This applies once an infection is underway.
First the larvae must be eliminated through pressure around
the lesion and the use of forceps. Secondly the wound must be
cleaned and disinfected. Further control is necessary to avoid
It is also possible to treat livestock with
the use of slow release boluses containing ivermectin which
can provide long term protection against the larvae development.
Sheep may be dipped, which involves drenching
the sheep in insecticide to prevent the growth of the larvae.
Use of Myiasitic maggots in Medicine
Through the ages maggots have been used in
medicine in order to clean out necrotic wounds. Companies exist
which produce sterile maggots which may be used to clean wounds
and promote healing. (to be finished... )