· The Oestridae are a family of flies
variously known as bot flies, warble flies, heel flies, gadflies, and similar names. Theirlarvae are internal parasites of mammals, some species growing in
the host's flesh and others within the gut. The human botfly, Dermatobia hominis, is the only species
of bot fly known to parasitize humans routinely, though other species of flies
do cause myiasis
· A botfly, also written bot fly, bott fly or bot-fly in various combinations, is any fly in the family Oestridae.
Their lifecycles vary greatly according to species, but the larvae of all species are internal parasites
of mammals. Largely according to species, they also are known variously as warble flies, heel flies, and gadflies. The larvae of some
species grow in the flesh of their hosts, while others grow within the hosts' alimentary tracts.
· The word "bot" in this sense means a maggot. A warble is a skin lump or callus such
as might be caused by an ill-fitting harness, or by the presence of a warble
fly maggot under the skin. The human botfly, Dermatobia hominis,
is the only species of bot flies whose larvae ordinarily parasitise humans,
though flies in some other families episodically cause human myiasis, and are
sometimes more harmful.
· The "bot" fly will hijack a mosquito to inject the
host with the eggs.
· The Oestridae now are generally defined as including the former
families Oestridae, Cuterebridae, Gasterophilidae, and Hypodermatidae as subfamilies.
· The Oestridae, in turn, are a family within the superfamily Oestroidea, together with the families Calliphoridae, Rhinophoridae, Sarcophagidae, and Tachinidae.
· Of families of flies causing myiasis, the Oestridae include the highest
proportion of species whose larvae live as obligate parasites within
the bodies of mammals. Roughly 150 species are known
worldwide.[5] Most
other species of flies implicated in myiasis are members of related families,
such as blowflies and screwworm flies in the Calliphoridae.
· Botflies deposit eggs on a host, or sometimes
use an intermediate vector such as the common housefly, mosquitoes, and, in the case of Dermatobia hominis, a species of tick. They are common in Belize. The smaller
fly is firmly held by the botfly female and rotated to a position where the
botfly attaches some 30 eggs to the body under the wings. Larvae from these
eggs, stimulated by the warmth and proximity of a large mammal host, drop onto
its skin and burrow underneath.[6]Intermediate
vectors 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.
· Myiasis can
be caused by larvae burrowing into the skin (or tissue lining) of the host animal.
Mature larvae drop from the host and complete the pupal stage in soil.
They kill the host animal, thus are true parasites.
· 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. When a horse rubs its nose on its legs, the
eggs are transferred to the mouth, and from there to the intestines,
where the larvae grow and attach themselves to the stomach lining or the small
intestine. The attachment of the larvae to the tissue produces a mild
irritation which results in erosions and ulcerations at this site.[8] Removal
of the eggs (which adhere to the host's hair) is difficult, since the bone and tendons are
directly under the skin on the cannon bones: eggs must be removed with a sharp
knife (often a razor blade) or rough sand paper, and caught before they reach
the ground. The larvae remain attached and develop for 10–12 months before they
are passed out in the feces. Occasionally, horse owners report seeing the
botfly larvae in horse manure. These larvae are cylindrical in shape and are
reddish orange in color. In one to two months, adult botflies emerge from the
developing larvae and the cycle repeats.[8] Bots
can be controlled with several types of dewormers, including dichlorvos, ivermectin,
and trichlorfon.
· 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.[9][10]
· The human botfly occasionally
uses humans to host its larvae. The larva, because of its spines, can pose an
extremely painful subepidermal condition. The fastest way to remove a botfly is
by putting a generous amount of iodine in the hole. The botfly will react instantly
by poking out of the hol. Another 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.[11] Additionally,
one can attempt to seal the breathing hole of the larva with nail polish or petroleum jelly;
after a day, with a clinical professional, the breathing hole is enlarged and
the larva is removed with forceps. Squeezing the larvae out is not recommended,
as it can cause the larvae to rupture; their bodily fluids have been known to
cause severe anaphylactic shock. 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.
· In cold climates supporting reindeer or caribou-reliant populations, large quantities
of Hypoderma tarandi (caribou warble fly) maggots are available
to human populations during the butchery of animals.[13]
· The sixth episode of season one of the television series Beyond Survival entitled "The Inuit - Survivors
of the Future" features survival expert Les Stroud and
two Inuit guides hunting caribou on the northern coast of Baffin Island near Pond Inlet, Nunavut, Canada. Upon skinning and butchering
of one of the animals, numerous larvae (presumably Hypoderma tarandi, although not explicitly
stated) are apparent on the inside of the caribou pelt. Stroud and his two
Inuit guides eat (albeit somewhat reluctantly) one larva each, with Stroud
commenting that the larva "tastes like milk" and was historically
commonly consumed by the Inuit people.
· Copious art dating back to the Pleistocene in
Europe confirms their consumption in premodern times, as well.