September 29th, 2013 by James Ayre
The human botfly (Dermatobia hominis) is a species of fly from the family Oestridae that is well-known for its love of human flesh, and its “interesting” means of parasitizing humans — bot fly larvae develop within the subcutaneous layers of human skin. And, yes, those who are unfortunate enough to become temporary hosts to the larvae can expect to feel them moving around underneath their skin. :/
The method of infection is itself rather interesting, the adult botflies capture mosquitos (or muscoid flies) and attach their eggs to the body of the mosquito or fly before releasing them, then when the mosquito or muscoid fly next feeds on a host the eggs either hatch and the larvae make their way into the open wound, or the eggs drop off and hatch shortly thereafter.
The larvae then spend the next eight weeks or so developing and feeding before they make their way out and pupate in the soil. They then emerge a week or so later as adults. theadults are rather large and somewhat resemble bumblebees. They’re easy to differentiate from most other species thanks to their lack of mouthparts.
The species is native to the Americas, and found from around — roughly — Southeastern Mexico to northern Argentina, Chile, and Costa Rica. It isn’t all that abundant though. The wounds generally don’t become infected, and the larvae a survival is dependent upon that — it’s thought that the fly larva may itself produce antibiotic secretions that help to prevent infection.
In addition to the human botfly there are quite a number of other species which do not target humans. As a whole the family of flies are variously referred to as: bot flies, bott flies, warble flies, heel flies, gadflies, and a number of other names. The larvae of most species live as internal parasites in mammals, sometimes in the host’s flesh, sometimes in the guts. While the human botfly is the only species known to parasitize humans routinely, other species of fly do cause myiasis in humans as well, occasionally. The word “bot” is in reference to “a maggot”.
Well-known relatives of the human bot fly that are known to cause myiasis in other animals include blowflies and screwworm flies.
Wikipedia provides further information:
Larvae from the eggs, stimulated by the warmth and proximity of a large mammal host, drop onto its skin and burrow underneath. Intermediate vectors (such as mosquitos, flies, ticks, etc) are often used since a number of animal hosts recognise the approach of a botfly and flee.
Eggs are deposited on animal skin directly, or the larvae hatch and drop from the eggs attached to the intermediate vector: the body heat of the host animal induces hatching upon contact or immediate proximity. Some forms of botfly also occur in the digestive tract after ingestion by licking.
The equine botfly presents seasonal difficulties to equestrian caretakers, as it lays eggs on the insides of horses’ front legs, on the cannon bone and knees, and sometimes on the throat or nose, depending on the species. These eggs, which look like small, yellow drops of paint, must be carefully removed during the laying season (late summer and early fall) to prevent infestation in the horse. In cattle, the lesions caused by these flies can become infected by Mannheimia granulomatis, a bacterium that causes lechiguana, characterized by rapid-growing, hard lumps beneath the skin of the animal. Without antibiotics, an affected animal will die within three to 11 months.
The human botfly occasionally uses humans to host its larvae. The larva, because of its spines, can pose an extremely painful subepidermal condition. One removal method is to use the tree sap of the matatorsalo, found in Costa Rica, which is reputed to kill the larva, yet leave its body in the skin. Additionally, one can attempt to seal the breathing hole of the larva with nail polish or vaseline, and then, after a day, squeeze out the suffocated, dead larva. Use of adhesive tape can work, but carries additional risk of infection because portions of the larva’s breathing tube can be broken off by the tape and make the remainder of the body difficult to remove.
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