The Red in Rudolph's Nose: Not a common cold.
In the average layman's eyes, the black mass with remnants of wings stuck on the end of a swatter is a "fly". Flies are flying everywhere, from the dead animal in the road, to the local dump, to the feces left by the dog next door, and then into the sanctity of your home. Rudolph the Red Nosed Reindeer may be the poster child for the ugly lifestyle and diversity of the fly. This article will introduce you to the fly, the lifestyle of the Reindeer Bot Fly and the Human Bot Fly, and the truly hideous, sometimes disfiguring, risks they pose to your health.
Background of the Fly
True flies are members of the Animal Kingdom just like you and me. They have two wings, and under each wing is a miniature undeveloped wing, shaped like a club, which is called a “haltere”. The halteres, and several other physical features they enjoy, are crucial to the annoying success of this insect.
The halteres provide stability and assist in coordination of the fly in flight. Coordination in three planes must be constantly adjusted, as well as the need for an occasional backward or spinning move. They also are sensory organs that detect flight conditions, and atmospheric and environmental stimuli such as temperature and wind.
Adult flies have other features that contribute to their functional success. The mouth-parts of a fly are strong and frightening. Their jaws contain muscular pumps, bulbous labella (lips), and some also have a piercing sty-let to start the flow of fluids they feed on, usually by parasitizing animals. They have acute vision and chemo-reception (sense of smell/taste). In the biting species of flies it's often only the female who bites and this behavior is usually associated with sexual reproduction.
The larval forms (young flies) of various species are the ones that are the most horrid and frightening to animals, including humans. Some are mere scavengers attacking only dead vertebrate tissues, and thus providing a necessary service to the dessication and recycling industries of nature. The others are referred to as “endoparasites” meaning they enter, live inside, and develop within live creatures.
Most fly larvae are born or hatch in a liquid environment ranging from moist earth or litter, to a fully aquatic environment such as a puddle or edge of a pond. Some use a breathing apparatus known as a “siphon tube” to penetrate a moist surface for air. Some can rely on dissolved oxygen taken in through tracheal gills (similar to fish gills). Some also have hemoglobin in their blood to store oxygen.
The larvae are very dissimilar to adult flies wherein they lack legs, haltares, wings, heads, segmentation, and many sensory organs. They do have similar mouth-parts with musculature for sucking and lapping. The larval forms discussed herein further derive their liquid diets, and their developmental housing from the flesh and blood of animal hosts.
The Reindeer Throat Bot Fly
This species is found in the upper northern hemisphere, particularly in the arctic zone. It's an endoparasitic carnivore of reindeer. The female gives birth “oviviparously” (meaning the eggs hatch inside of her). She then enters a reindeer's nostril and ejects the larvae from the hatched egg onto the inner nasal tissues. When finished, she quickly exits and her larval offspring latch on to, and feed upon, the soft mucosal flesh and blood vessels of the nasal and pharyngeal cavities.
Movement of the larvae inside these cavities can prove very distressful for a reindeer, causing it to repeatedly sneeze and cough. The infestation is not usually life threatening to the animal unless the larvae travel to and parasitize the lungs. The larvae complete their development within the host reindeer after approximately 10 months. They then migrate back to the front of the nostrils where the reindeer's sneezing expels them.
The Human Bot Fly
Few people know that there exists a Human Bot Fly, sometimes referred to as the “Torsalo Fly”. It's also a parasitic carnivore, and is found in tropical regions. This fly does not enter its human host through open body cavities like the Reindeer Bot Fly. Instead a productive female captures a biting fly species, or a tick or a mosquito, and lays her eggs on its sternum. She then releases her captive who transfers the eggs to the human host. The eggs fall off the transporting insect, immediately hatch and penetrate the human's skin. Once inside they grow and develop until they are ready for their pupal stage of life, at which time they bust out of the person and fall to the ground.
Sites of infestation can occur all over the body. They not only get under people's skin, but they also get into mucosal tissues in cavities such as eyes, ears, nose, mouth and gums, and the mucosa of other orifices.
Unlike the Reindeer Bot Fly, the Human Bot Fly poses a substantial risk of directly introducing secondary infections because when it bores into the skin it creates open exposed lesions. The lesions remain open to some extent because the embedded larvae need to breathe; they use their siphon tube to maintain an air vent to the outside. As with the Reindeer Bot Fly, the other danger posed is possible migration to other body parts and organs.
Bot Fly Removal
The treatment to remove infestations of bot flies is simple if a secondary infection has not occurred, and if the lesions are small and accessible. Because these creatures need to breathe, and use siphon tubules to the outer surface of the skin, they recommend covering the area with something thick like petroleum jelly to block the passage of air. This will force the creature to surface where it can be plucked out.
If the larvae are still in early stages and too small to be wholly removed, some doctors may recommend waiting until they reach a maturity and size that can be better manipulated. More complicated cases may require antibiotics, and even surgery.
Minimizing Risk of Infection
Infections are rare in the United States, but risks increase as you move farther south into the subtropics and tropics. The following are proactive strategies that can minimize your health risk of getting such an infection:
- Frequent handwashing with clean, potable water.
- Wearing Protective clothing.
- Using DEET and other approved insect repellents on your skin and hair.
- Treating clothing, bedding, tents, etc. with approved Permethrin.
- Eliminating breeding grounds for insects such as ticks and mosquitoes in your yard. Cut your grass, fill holes that fill with puddles, don't openly compost or store garbage, etc.
- Use a bug zapper. Kids love the racket style zappers, but tell them not to touch the dead bugs, and clean the racket with an approved chlorine disinfectant often.
Berenbaum, May R., Ninety-nine More Maggots, Mites, and Munchers, (Chicago: University of Illinois Press, 1993)
Swan, Lester A. and Papp, Charles S., The Common Insects of North America, (New York: Harper and Row Publishers, 1972).
O'toole, Christopher, Ed., The Encyclopedia of Insects, (U.K.: Equinox (Oxford) Ltd., 1986.
U.S. Army Public Health Command, Publication 18-052-0110, January 2010 http://phc.amedd.army.mil/PHC%20Resource%20Library/HumanBotFlyMyiasisJan2010.pdf
Centers for Disease Control http://www.cdc.gov/parasites/myiasis/