Human Bot Flies - Living in your skin
Your pain is their homeostasis
The human immune system is an amazing adaptation. Incorporating a number of barriers and defenses, the immune system protects the body from a variety of bacteria, viruses, and other organisms that would otherwise find the warm, moist internal environment very attractive, (Pack, 2001). Although the body’s defenses do a good job of keeping out most unwanted invaders, there are a number of organisms that have found ways around those defenses and make a good living at it, (Pack 2001). One of those organisms is the Human Bot Fly. The Human Bot Fly not only makes a good living at bypassing immune defenses, it could not exist without that ability.
When I first learned that such creatures existed, I was intrigued, but not concerned. I knew of Bot Fly infestations on horses, but thought the problem was species limited. When I learned that some Bot Flies choose human hosts, I was not only a bit frightened, I was curious as well. I wanted to know which flies to worry about, where they lived, and how they did what they do? How do they avoid immune defenses? How dangerous is an infestation? And, most importantly, How much am I at risk? I wanted to know about these creatures so I could better avoid them, and be more able to diagnose their presence should the need ever present itself. Yet, in this case, the knowledge I gleaned from my research not only helped ease my fears, it also helped increase my understanding of homeostasis as well.
Homeostasis is the achievement of a natural balance or equilibrium that allows life to continue, (Pack, 2001). Just as there are systems within the body to help achieve this balance, there are also larger systems in the environment that work similarly, almost unnoticed, to keep the world functioning normally as well. Whether we realize it or not, the human organism is part of the larger system, and, like an organelle of a cell, must play its part to maintain homeostatic balance in the world. In the case of the Human Bot Fly, our warm, human bodies simply provide the incubator without which that species would cease to exist.
Using a system of phoresis, (attaching eggs to unwitting carriers as a vector for implantation), (Vexman, 2004), the Human Bot Fly, (Dermatobia Hominis), captures mosquitoes, ticks or other biting insects, holds them down, and adheres a number of eggs to the body of that creature, (Vexman, 2004). When the carrier seeks out its warm-blooded prey to continue its own life cycle, the warmth of the mammalian body incubates the eggs that hatch larvae that drop to the skin. The larvae then enter the body through hair follicles, through the bite site, or by directly burrowing into the skin, (Bhandari, 2007). This type of infestation is Myiasis, and is common in a number of fly species, (Exotic Myiasis, 2010). Using one of the human’s own immune defense barriers, the skin, to shield it from outside danger, the myiastic larvae stay warm with body heat behind the shield of the skin while gorging on living tissue and blood. They also secrete their own antibiotics to fend off competition from bacteria and fungi in the area.
Unless removed, the maggot will feed continually for five to twelve weeks causing severe pain and itching in the host, (Exotic Myiasis, 2010). Once matured, the larvae drop to the ground to pupate into adults, (Bhandari, 2007). It seems their only purpose in life is to continue the species since adults only live for a few hours while they seek out a mate, fertilize eggs, and plant them on a new carrier to continue the process anew. Adults never even eat. They live entirely on the stores built up while gorging on host flesh as larvae. Fortunately, even though they are called Human Bot Flies, they seldom infest humans and actually prefer to infest other warm-blooded animals that are easier to find, (Bhandari, 2007).
The only real beauty I can find in the animal is the way its life cycle gives an abstract representation of homeostatic balance. For homeostatic balance, or equilibrium to remain constant, the cyclical process of making, using, and renewing must be held within certain norms, (Pack, 2001). If one element is missing or cannot be balanced, the entire system can be thrown out of line and result in death of the organism. For the Bot Fly, if it cannot find a carrier for its eggs, or the eggs do not reach the warm-blooded host, the entire life cycle is disrupted, and, if this occurs often enough, the entire species could cease to exist. With humans, we have homeostatic balances, too, and if enough of ours fall outside the norms often enough, we, too, could cease to exist.
I do not know if the antibodies released by the Bot Fly larvae provide any benefit to their host, but there are some species of flies whose larvae have been proved beneficial. The maggots of certain Blow Flies have been used medicinally since the 15th Century to help fight infection and heal wounds, (WCIM, 2010). Exactly how this works is not known, but it is suspected that antibiotic chemicals released by the maggots attack bacteria, and, at least in the case of Blow Fly maggots, they only eat dead flesh, (WCIM 2010). Maggot therapy has been used with great success in burn wounds, and the otherwise non-healing wounds of diabetics, (WCIM, 2010).
I still cringe at the thought of a maggot chewing on my flesh, even if it is necrotized flesh, and even though I understand my body is host to any number of other parasites, it is reassuring to know that such creatures may actually have a useful function and some medicinal value. It is also reassuring to know that Human Bot Flies are not found in any region of the world I frequent, and, despite their name, may not even prefer human hosts. Still, the most important lessons learned from these creatures are the lesson about harmonic balance in nature, and the lesson about homeostasis. In the absence of important links in its life cycle, the Human Bot Fly ceases to exist. In the absence of important links in the human life cycle, we, too, cease to exist.
Bhandari, Ramanath, Janos, David P., and Sinnis, Photini, “Furuncular Myiasis Caused
by Dermatobia Hominis in a Returning Traveler” PubMed Central,
www.ncbi.nim.nih.gov/pmc/articles/PMC1853312/ 2007, Accessed March 2010
Diptera Site, The, www.sel.barc.usda.gov/Diptera/oestrid/Dermatobia%20homonis%20
HOME.html, 2010, Accessed March 2010
Exotic Myiasis, - The Department of Medical Entomology, www.medent.usyd.edu.
au/fact/myiasis.html, 2010, Accessed March 2010
Pack, Phillip E., Ph.D., “Cliffs Quick Review Anatomy and Physiology,” Wiley
Publishing, Hoboken, New Jersey, 2001
Vexman.com – www.vexman.com/botfly.htm Accessed March 2010
WCIN – Wound Care Information Network, www.medicaledu.com/maggots.htm.
Accessed, March 2010