Nasal Bot Flies
Although unpleasant looking, nasal bot fly larvae do not harm deer and do not infect humans (Southeast Wildlife Disease Study photo).
Nasal bot flies (Cephenemyia spp.) are common parasites that infest the nasal passages of deer. Most often, taxidermists find them while preparing heads for mounting, although hunters occasionally notice them.
Adult female flies deposit small larvae in the nostrils of the deer. The larvae enter the nasal passages and pass through several stages of development and growth. They are liberated when the deer sneezes. They then form a pupa and emerge as an adult fly.
Although quite large (up to 1 and 1/2 inches) and unpleasant looking in the final stages of development, nasal bots cause little harm to the deer and do not infect humans. They also do not affect meat quality.