Myiasis
From Wikipedia, the free encyclopedia
| ICD-10 | B87 |
|---|---|
| ICD-9 | 134.0 |
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" and "fly-blown".
German entomologist Fritz 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."
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[edit] Classifications
Two different classifications of myiasis can be adopted:
- The classical classification describes the myiasis by the infected area of the host. This is the classification used by ICD-10. For example: dermal, sub-dermal, cutaneous (B87.0), nasopharyngeal (B87.3), ocular (B87.2), intestinal/enteric (B87.8), or urogenital (B87.8).
- 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 or facultative or accidental.
[edit] Flies responsible for Myiasis
There are three main fly families causing economically important myiasis in livestock and also, occasionally, in humans:
- Oestroidea (botflies)
- Calliphoridae (blowflies)
- Sarcophagidae (fleshflies)
Other families occasionally involved are:
The adult flies are not parasitic, but when they lay their eggs in open wounds and these hatch into their larval stage (also known as maggots or grubs), the larvae feed on live and/or necrotic tissue, causing myiasis to develop. They may also be ingested or enter through other body apertures.
[edit] 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).
[edit] Prevention
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 method 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 wool from around the tail and between the rear legs, which is a favourable environment for the larvae. Another more permanent practice which is used in some countries is mulesing, where skin is removed from young animals to tighten remaining skin - leaving it less prone to fly attack.[1] PETA have been campaigning to have farmers cease mulesing, they have used celebrities such as Pink, Toni Collette and Chrissie Hynde have also participated in PETA's campaign against the mulesing practice.[2]
[edit] Treatment
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 further reinfection.
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.
[edit] Use of Myiasitic maggots in Medicine
Through the ages maggots have been used in medicine in order to clean out necrotic wounds. For more information, see Maggot therapy.
Maggot Therapy (also known as Maggot Debridement Therapy (MDT), larval therapy, larva therapy, or larvae therapy), is the intentional introduction by a health care practitioner of live, disinfected maggots or fly larvae into the non-healing skin and soft tissue wound(s) of a human or other animal for the purpose of selectively cleaning out only the necrotic (dead) tissue within a wound in order to promote wound healing.
