This rare and quite disgusting condition is known as myiasis, an infection or infestation of the body of animals, and more rarely humans with the larva of botflies and related species. In other words: maggots in your body.
Primarily a veterinary issue with livestock, human infestations is rare in the United States. It is more frequently seen Central and South America.
A relatively large fly, the botfly would find it very difficult to place its eggs on a person. To rectify the situation, the clever botfly hijacks a much smaller mosquito in flight attaching its eggs to the vector. It then releases the mosquito and it goes on its way looking for a blood meal.
When the mosquito does take a blood meal, either on a human or an animal, the body heat of the mammal causes the eggs to hatch. At this point the newly hatched larvae burrow into the host and reside in the tissue.
Some species of dipteran flies may actively try to place the eggs in the eye (ocular myiasis). This sometimes occurs to people working with livestock in underdeveloped countries.
In the skin or eye the larva matures to a relatively large size over a period of a couple of months. When completely mature, the larva emerges from the tissue and drops to the ground where it becomes an adult fly and the cycle repeats.
The symptoms in the person begin with a nodule that contains one larva. The nodule continuously seeps blood and pus because the larva needs to keep the wound open to breath.
The can be itching and occasionally serious pain when the larva moves. Secondary bacterial infection can occur.
To treat botfly infestation is to remove the larva. Cutting off the air supply (using Vaseline, tape, etc.) causes the larva to emerge and can then carefully be pulled out with tweezers. They can be difficult to remove because of backward facing barbs that secure it in the hole. Some people choose to let the larva develop and emerge naturally.
Surgery in not usually necessary unless the larva dies in the tissue and cannot be removed. The use of insect repellent and protective clothing that prevent mosquito bites can help prevent infestation.