Classifications
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 hosts dead or living tissue, liquid body substances, or ingested food". For modern purposes however, this is too vague. For example, feeding on dead or necrotic tissue is not generally a problem except when larvae such as those of flies in the family Piophilidae attack stored food such as cheese or preserved meats; such activity suggests saprophagy rather than parasitism; it even may be medically beneficial in maggot debridement therapy (MDT).Currently myiasis commonly is classified according to aspects relevant to the case in question:

The classical description of myiasis is according to the part of the host that is infected. This is the classification used by ICD-10. For example:dermal
sub-dermal
cutaneous (B87.0)
creeping, where larvae burrow through or under the skin
furuncular, where a larva remains in one spot, causing a boil-like lesion
nasopharyngeal, in the nose, sinuses or pharynx (B87.3)
ophthalmic or ocular, in or about the eye (B87.2)
auricular, in or about the ear
gastric, rectal, or intestinal/enteric for the appropriate part of the digestive system (B87.8)
urogenital (B87.8)
Another aspect is 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, where the parasite cannot complete its life cycle without its parasitic phase, which may be specific, semispecific, or opportunistic
facultative, incidental, or accidental, where it is not essential to the life cycle of the parasite; perhaps a normally free-living larva accidentally gained entrance to the hostAccidental myiasis commonly is enteric, resulting from swallowing eggs or larvae with ones food. The effect is called pseudomyiasis. One traditional cause of pseudomyiasis was the eating of maggots of cheese flies in cheeses such as Stilton. Depending on the species present in the gut, pseudomyiasis may cause significant medical symptoms, but it is likely that most cases pass unnoticed. Prevention
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 (including 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 method is the sterile insect technique (SIT) where a significant number of artificially reared sterilized (usually through irradiation) male flies  are introduced.