Migratory myiasis involves the presence of fly larvae in the dermis and subcutaneum that migrate aimlessly.


Genera of flies involved with humans:

(1) Gasterophilus (horse bot fly)

(2) Hypoderma (cattle bot fly)


The larvae are unable to complete their life cycle in humans.


Risk factors for migratory myiasis:

(1) exposure to host animal (horse, cattle)

(2) presence of bot flies

(3) presence of other cases in the community


Clinical signs and symptoms:

(1) raised area of skin that migrates for weeks to months

(2) pruritus


Laboratory findings:

(1) hypereosinophilia

(2) presence of hypodermin C in the serum (for Hypoderma species)

(3) PCR


The larva can be seen by placing a drop of mineral oil over the advancing edege and looking at the site under a dissecting microscope or other magnifier. Alternatively the larvae can be visualized on ultrasonography.


Complications may include:

(1) cellulitis

(2) pustules

(3) migration to the lungs, brain or othe organs


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