Once hatched, the larvae then lacerate the skin with their mouthparts, causing open sores. Once the skin has been breached, the larvae then tunnel through the sores into the hosts subcutaneous tissue, causing deep and irritating lesions highly subject to infection. After about the second day, bacterial infection is likely and, if left untreated, causes bacterial bloodstream infections or sepsis. This leads to anorexia and weakness and is generally fatal if untreated. Human vectors
There are three main fly families causing economically important myiasis in livestock and also, occasionally, in humans:
Calliphoridae (blowflies)
Some examples include Calliphora vomitoria and Calliphora vicina
Oestridae (botflies)
Sarcophagidae (fleshflies) Sarcophaga barbata are usually found in dead and rotting meat and animal excrement, which are prime environments for them. This is because their larvae are facultative parasites, as they feed on organic tissue and use the hosts oxygen reserve.Other families occasionally involved are:
Anisopodidae
Piophilidae
Stratiomyidae
Syrphidae

Specific myiasis
Caused by flies that need a host for larval development
Dermatobia hominis (human botfly)
Cordylobia anthropophaga (tumbu fly)
Oestrus ovis (sheep botfly)
Hypoderma spp. (cattle botflies or ox warbles)
Gasterophilus spp. (horse botfly)
Cochliomyia hominivorax (new world screwworm fly)
Chrysomya bezziana (old world screwworm fly)
Auchmeromyia senegalensis (Congo floor maggot)
Cuterebra spp. (rodent and rabbit botfly)

Semispecific myiasis
Caused by flies that usually lay their eggs in decaying animal or vegetable matter, but that can develop in a host if open wounds or sores are present
Lucilia spp. (green-bottle fly)
Cochliomyia spp. (screw-worm fly)
Phormia spp. (black-bottle fly)
Calliphora spp. (blue-bottle fly)
Sarcophaga spp.
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.