Bot Flies

Flies have an annoying habit of getting up close and personal. Many flies and gnats will buzz around your head and irritate your eyes and skin. Mosquitoes and deer flies will buzz around and bite. However, the bot fly goes one step further. Bot fly larvae develop on the live tissue of mammals.

Human bot flies are present in the Americas from Southern Mexico to Chile. Human bot flies are slow awkward fliers that avoid direct contact with mammals. Instead, these bot flies will lay eggs on other flies that then carry the bot fly eggs or larva to their human host. Most often the bot fly will capture a mosquito, a housefly or other Muscoid fly (house fly family) to do its dirty work. The bot fly larva burrows under the skin and feeds on the fluids and tissues of the host.

Most often, the human bot fly develops in the head, but it can develop in other tissues. In other tissues, bot flies can burrow into muscle and cause damage to the tissue. In the head, the skull keeps the bot fly safely away from the brain and the bot fly will cause the tissue to swell and itch. The bot fly breathes air through a hole in the wound. Even though the wound is open to the air, bot fly wounds are not known to become infected unless the bot fly dies within the wound. The bot fly larvae may secrete antibacterial substances that prevent infection

If infested, it is a good idea to remove the bot fly. Covering the hole with petroleum jelly will encourage the bot fly will push out of the wound in order to breathe. When the bot fly is partly out of the hole, it can be grasped with forceps and steadily pulled from its hole. Once removed, the wound can be treated as would any other wound.

A number of human bot fly videos are posted on Youtube including this one: