Bot Fly, aka Torsalo or Dermatobia hominis
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Anterior Orbital Myiasis Caused by Human Botfly (Dermatobia hominis)
Capt Randall L. Goodman, USAF, MC; Col Michael A. Montalvo, USAF, MC; Maj J. Brian Reed, USAF, MC; LTC Frank W. Scribbick, USA, MC; Chad P. McHugh, MPH, PhD; Randall L. Beatty, MD; Ricardo Aviles, MD
A 5-YEAR-OLD boy with inferior orbital swelling and an erythematous mass arising from the inferior cul-de-sac of his right eye (Figure 1 and Figure 2 to the right) was seen by an Air Force Mobile Ophthalmic Surgical Team working in a rural area of the Republic of Honduras. The respiratory pore of a late-stage larva of the human botfly (Dermatobia hominis) was located in the anterior orbit. The larva was gently removed under general anesthesia through a small incision in the conjunctiva (Figure 3, Figure 4, and Figure 5 to the right).
Figure 1. Five-year-old Honduran boy with right inferior orbital swelling and erythema.
Figure 2. Examination under anesthesia, demonstrating right eye chemosis and inferior cul-de-sac mass.
Figure 3. A large white larva being removed from the right anterior orbit through a conjunctival incision.
Figure 4. Complete late-stage human botfly larva immediately after removal.
Figure 5. Based on the morphology of the anterior and posterior spiracles and the exterior spines, the larva was determined to be a mature larva of the human botfly (Dermatobia hominis).
Ophthalmomyiasis refers to the invasion of the lids, conjunctiva, cornea, and rarely the orbit or globe of the mammalian eye by fly larvae (order Diptera). The sheep nasal botfly (Oestrus ovis) is the most common cause of ophthalmomyiasis.1 The human botfly (D hominis) is the most common cause of cutaneous myiasis in Central and South America, but few cases of external ophthalmomyiasis and no previous case to our knowledge of orbital invasion have been reported.2
The female botfly glues her eggs onto the abdomen of a captured mosquito or other common fly. When the carrier insect lands on a human, the larva, or bot, hatches, burrows into the skin, and positions itself "head down" to feed, breathing through caudal respiratory spiracles. A furuncle with a central pore develops as the bot matures, molting twice until reaching 18 to 24 mm. The larva withdraws through a central punctum, falling to the ground and pupating before emerging as a mature botfly.3 Chloroform or lidocaine to anesthetize the bot may facilitate surgical removal as does occluding the breathing hole with ointment, beeswax, chewing gum, or pork fat.4
Capt Randall L. Goodman, USAF, MC
Randall L. Beatty, MD
Ricardo Aviles, MD
1. Savino DF, Margo CE, McCoy ED, Friedl FE. Dermal myiasis of the eyelid. Ophthalmology. 1986;93:1225-1227.
2. Wilhelmus KR. Myiasis palpebrarum. Am J Ophthalmol. 1986;101:496-498.
3. Lane RP, Lowell CR, Griffiths WA, Sonnex TS. Human cutaneous myiasis: a review and report of three cases due to Dermatobia hominis. Clin Exp Dermatol. 1987;12:40-45.
4. Elgart ML. Flies and myiasis. Dermatol Clin. 1990;8:237-244.
There’s an insect nominated as the most disgusting, most vile,
most revolting insect ever to fly on the face of this planet.
And it comes straight to you (I mean that literally) from the
tropics of Central and South America.
You might want to keep a fly swatter nearby.
After you read this, it might really come in handy.
BOT FLY SONG
it wiggles, lays eggs, its hooks sure do pinch!
or later its bound to come out
pops the maggot, how many? You
Bot Fly. It’s Bot Fly
worst of its kind
Bot Fly. It’s Bot Fly
in for a bind
Bot Fly. It’s Bot Fly
the worst of its race
rather have pimples all over my face.
Bot Flies not only make great songs to sing around a campfire on a
cold and crispy night, but they also come in all sorts of varieties to
meet your every individual need.
Then there’s the Horse Bot Fly.
These Bot Flies favorite pastime is laying their eggs on horse’s
knees, lip hairs, jaws, cheeks, and horse’s food.
When the horses eat the egg-infested food, maggots hatch inside the
horse’s stomach and intestines where they irritate the mucous linings of
the intestines, rectum, and anus, making horses restless.
Some of the maggots crawl their way up the horse’s throat and
into the horse’s mouth where they happily invade the tongue, gums, and
mouth lining of the horse. These
happy little maggots party like there’s no tomorrow for 7 to 10 months
on a major food binge!
But the winner of the prestigious “Revolting Insect of the Year
Award” goes to our dear friend, the Human Bot Fly, for its sincere
demonstration of love and compassion towards the human race.
These pesty flies are very good at what they do.
They’re the Navy Seals of the insect world.
Human Bot Flies are not your average housefly.
They are scientifically classified as Dermatobia hominis, or
myiatic flies. You’re
probably asking yourself what in the world does myiatic hominis mambo
jumbo mean? I don’t think
you’ll be thrilled to know, but hey, because I’m such a nice person,
I’ll tell you anyway.
Since these guys are myiatic, they don’t waste time frolicking in
your garbage cans. They go directly to the source, and yes my dear friends,
their favorite food on the menu is you!
In this article we will discover together the wonderful world of
Human Bot Flies. You will
share in the joys of maggot birth and the miracle of puberty as these
magnificent flies eject ceremoniously from underneath your skin and open
their eyes for the very first time.
Human Bot Flies are not tiny flies.
They’re pretty large and are nearly the size of bees.
They have a yellowish head, huge bluish-black thorax or body, with
orange legs and brown wings. These
flies have an extremely powerful urge to reproduce.
If they were to fly towards you, not only would you hear their
annoying buzz and notice how big they are, but you also would immediately
try squashing them with your shoe.
As you’ll soon find out, Bot Flies are not only cunning,
they’re gifted with an IQ equal to Einstein.
They know the impending doom that awaits them if they’re seen
flying in your home, let alone near you.
So what do they do? They
fly out and seek a mosquito or tick.
The lower their IQ count the better.
The Bot Fly then holds the mosquito’s wings to prevent it from
escaping. It then glues about
15 to 30 eggs at a time on the abdomen of the bloodsucking mosquito.
When the Bot Fly lets go of the mosquito’s wings, the mosquito
flies away carrying the Bot Fly eggs.
The mosquito then prepares for landing on your warm body.
As the mosquito sucks on your blood, your body heat begins to hatch
the Bot Fly eggs on the abdomen of the mosquito.
Once the eggs hatch and the mosquito takes off to find more blood
to suck on, the tiny baby maggots burrow into your skin.
It takes about 5 to 60 minutes for these baby maggots to burrow
completely under your skin, either through a hole they make for themselves
or through the bite hole made by the mosquito.
You won’t even feel a thing, not yet anyway.
These baby maggots position themselves head down inside your skin with 2 oral hooks which they use to tear your tissue while they feed on you. The rows of curved spines along their body help anchor the maggots onto your skin. While the maggots feed on you they make a hole in your skin so they can breathe and excrete waste. For 6 to 8 weeks the maggots begin to grow big and strong, munching deliciously away on you. As they mature, you’ll begin to develop sores that itch like crazy. These itchy sores will then develop into egg-size painful boil-like sores that house the growing maggots and often ooze. You will then feel a stabbing painful feeling due to the maggots tearing off your tissue while feeding and from their spines irritating your tissue as they squirm around. You’ll be able to see and feel the maggots move and wiggle under your skin. How gross! Once the maggots grow fairly large, they will eat their way out of your skin where they fall to the ground and continue to pupate into adult flies. The entire horrible life cycle, from birth to adult, takes around 3 months.
legendary explorer Colonel Percy Harrison Fawcett, who ventured into the
unknown tropical wilderness of South America, wrote about these Human Bot
Flies. The natives called
them “Sututus.” Let us
allow Colonel Fawcett to relate his encounter with the Sututus.
“Sututus were another trial for some of us: these are the grubs
of a moth or mosquito which, after hatching from eggs left on the shirt,
immediately bury themselves under the skin-usually on the back.
The little brutes could not be extracted until the sore they made
was “ripe,” and even then it was an art to get them, for on being
molested they clung to the flesh with sharp mandibles.
Tobacco juice sometimes helped, but killing them under the surface
could bring on blood poisoning. Later
on, the Indians undertook the cure in their own way.
They would make a curious whistling noise with their tongues, and
at once the grub’s head would issue from the blowhole.
Then the Indian would give the sore a quick squeeze, and the
invader was ejected.”
There’s a wonderful site on the Web where people who’ve had
encounters with the Human Bot Fly can post their horrible stories.
Brenda and Mark Johnstone officially started the website after
Brenda’s husband Mark was bitten not once but twice in the scrotum.
On November 24th, 2000 Mark and Brenda remember
traveling to Costa Rica to observe the magnificent Volcano Arenal eruption
from the Los Lagos observatory. At
night, while Mark is changing his clothes, he feels a mosquito bite on his
scrotum. Right away he begins to experience a strange pain in his
scrotum. When he mentions it
to Brenda they both talk about what on earth it could be, whether it’s a
spider bite or an infected mosquito bite.
Brenda remembers reading something in the guidebook Explore
Costa Rica by Harry S. Pariser, from their first honeymoon trip to
Costa Rica. The author
mentions in the book a strange bug called the “Bot Fly (Dermatobia
hominis), whose larvae mature inside flesh. An egg-laden female botfly captures a night-flying female
mosquito and glues her eggs on to it.
When the mosquito is released and bites a victim, the host’s body
heat triggers an egg to hatch. It
falls off and burrows in. The
larva secures itself with two anal hooks, secreting an antibiotic into its
burrow, which staves off competing bacteria and fungi.
Its spiracle pokes out of the tiny hole, and a small mound forms
which will grow to the size of a goose egg before the mature larva falls
Should you be unfortunate enough to fall prey to a larvae- an
extremely unlikely occurrence for the average visitor- you have
three cures available. One is to use acrid white sap of the matatorsalo (bot
killer), which kills the larva but leaves its corpse intact.
Another is to apply a piece of soft, raw meat to the top of the air
hole. As the maggot must
breath, it burrows upward into the meat. A third is to apply a generous helping of Elmer’s glue or
cement to the hole. Cover
this with a circular patch of adhesive tape; seal this tape with a final
application of glue. Squeeze
out the dead larva the next morning.
The only other alternative is to leave it to grow to maturity,
giving you an opportunity to experience the transmogrification of part of
yourself into another creature. It
only hurts when the maggot squirms and if you swim, presumably because you
are cutting off its air supply. Don’t
try to pull it out because it will burst.
Part of its body will remain inside and cause an infection.”
Brenda knows right away what is bothering Mark.
They go online to find more information on the Bot Fly with no
success. When they return home Mark begins to notice 2 lumps in his
scrotal skin, causing him severe and intense shooting pain throughout his
scrotum and perineum.
December 17th, 2000 Brenda brings Mark to the emergency room
after a painful episode. While
Mark sits on the examining table, a lady doctor picks up Mark’s chart
and says, “I’m not touching that!”
Wait a minute. I
thought it was lice?
Hours go by. A
doctor finally arrives and Mark and Brenda tell him their horrible story.
The doctor stares skeptically at them and asks, “What other
doctors are you seeing? Are
you on any kind of medication?” The
doctor then excuses himself and tells them he has to make a call to the
Urologist concerning the matter at hand.
What does the doctor really do?
He hurries to his computer and types the word “Bot Fly” on the
Internet search engine. Brenda
sneaks up behind him and says,” There is a lot more information on the
net if you want me to show you where it is at!”
The doctor, taken by surprise, turns around and defends himself
saying the Urologist is on his way. It’s
obvious the doctor did not know what Mark had.
If doctors don’t know they should say so.
Dr. Michael Rashid, MD Resident of Urology, enters the scene
shortly after. Dr. Rashid
believes Brenda and Mark’s story, even though he is somewhat skeptical.
They set an appointment for Tuesday, December 19.
When the day comes, Dr. Gabriel Rodriguez, MD and Assistant
Professor of Urology, examines Mark.
Off they go to the operating room where vasectomies are usually
performed. Brenda is allowed
to be with Mark during the operation.
After Mark is prepped for surgery, the doctor, with Mark’s
consent, takes photos of the sores. Dr.
Rodriguez tells Mark he has to cut deeper into the tissue.
All of a sudden, Dr. Rodriguez’s jaw drops open in surprise.
He exclaims, “It’s alive!” and tells the attending nurse to
get a container and drop the Bot Fly maggot inside.
While the nurse is checking out the maggot, Mark tells the nurse,
“I read on the internet that those things can jump 6 feet!”
The nurse quickly slams the lid tight on the container and sets it
down. Brenda takes the
container and brings it over to Mark.
They both watch the large maggot squirm and wiggle about.
The doctor closes up the area in Mark’s scrotum and begins to get
ready for Bot Fly #2.
When they extract Bot Fly #2 it is still alive, obviously enraged
that it was taken out of a cozy and warm environment.
All this reminds Brenda and Mark of the movie Alien.
Brenda says how one day Mark is complaining on how uncomfortable
the stitches are. She simply
tells him, “Well now you have a little knowledge of what childbirth is
but I had twins!” Mark replies.
Mark has healed and is doing fine.
They even have a special poem written to the version of “Twas the
Night Before Christmas” by Bryan Springer about their ordeal.
Their website on Bot Fly stories is a must read!
It helps educate the unknown public about these vicious pests.
If you ever find yourself traveling to the tropics of Central and
South America and you feel a Bot Fly maggot crawling under you skin, here
are some proven remedies that will help get rid of your new friend.
HOW TO GET RID OF YOUR BOT FLY (without doctor
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Several parts of this story and the photos are from Brenda Johnstone, http://www.vexman.com/botfly.htm, or for more stories about botflies click here. You can email Brenda at firstname.lastname@example.org. Much thanks to her for her information and her permission for us to use it.