Do you know what a Human Botfly is?.......Well you will after reading this!

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Volcano Arenal

While viewing the very active volcano Arenal in the small town of La Fortuna in Costa Rica Mark was bitten by a mosquito. This happened on November 24th, 2000 at night in the viewing area of Los Lagos.
Upon returning home from Costa Rica Mark started experience a strange pain in his scrotum. He finally mentioned it to me (his wife) & we talked about what it could be. Spider bite? Infected mosquito bite? Then I remember reading something in the guide book from our 1st (honeymoon) trip about a weird bug in Costa Rica. The guide book Explore Costa Rica by Harry S. Pariser said.... "Botfly (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 out. Should you be unfortunate enough to fall prey to a lava - an extremely unlikely occurrence for the average visitor - you have three cures available. One is to use the 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 airhole. 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." Thank you for adding that bit to your guide book Harry. (If we had not read that I am not sure what would have happened to Mark). Harry S. Pariser is the author of Explore Costa Rica & Explore Belize

I had even highlighted this information & remembered telling Mark" listen to this". Well since we are not the average visitor I knew this had to be what was bothering Mark. We tried the raw meat but guess the botfly didn't like the cut of meat Mark used as it didn't work. We then got on the internet for more information (it didn't look good) & found this site (below) & others to confirm in our minds that this is what the problem was.



The pain was not like the book described, Mark was getting bitten at random times. Mostly when he tried to sleep & different times at work. Since he is a great bearer of pain he decided to call UTMB to see if anyone there wanted to do a case study on this rare occurrence. He was told to email the "WHO Collaborating Center for Tropical Diseases". He did so giving full detail as to what happened, meanwhile I made him a Drs appointment with our general Doc. This Doctor decided that Mark must have lice & gave him lice medicine. Meanwhile the botfly's got bigger & the biting worse. Customers even noticed it & said something to me. How do you explain?

Below are photos of Volcano Arenal in Costa Rica taken at the
Los Largos Observatory where Mark was bitten by the botfly.

Volcano Arenal, Coast Rica

Volcano Arenal in Costa Rica

You can see the smoke clearing  off the top of Volcano Arenal as Mark (on the right) & Wendy watch it erupt. During the day you could see the larva smoke coming down but at night it was a spectacular show of red/orange glow.

To the left of Volcano Arenal you can see the destruction (notice the black area next to the trees) from the August 2000 eruption. Los Largos closed there main campground and you can see how close the lava came by the water toys on the lake. We hiked around the 2 lakes...very pretty.

Mind you all this was going on during the Xmas season & the computer store was busier than ever. We were working on a Sunday (Dec. 17th, 2000) afternoon trying to get caught up when Mark went down on his knees in pain. It scared Cole & I so bad that I knew we had to get rid of these things somehow. I talked Mark into going to the emergency room where upon explaining to the attendant what was going on a young guy sitting beside her said "I have heard of botfly's before"! We both asked him what he knew & where he had heard about botflys from. He told us that he heard about them on the Discovery Channel but didn't know much. Wish he had been a doctor!
Going to the emergency room I watched at the door as Mark laid on the examining table totally depressed. One lady Doc picked up Marks chart & said "I'm not touching that"! Hours later a Doc arrives & we tell him the story. He asked us "What other DR's are you seeing & are you on any kind of medication"? He then tells us he has to call in a urologist.  Meanwhile he goes to a computer & types in "botfly" I sneak up behind him & say......there is alot more information on the net if you want me to show you where it is at! He turned to me in surprise & say's "no, the urologist is on his way from home". Enters Dr. Michael Rashid, MD Resident of Urology. He believes us but is skeptical. We sets up an appointment for the following Tue. AM. Meanwhile Mark is still experiencing terrible pain till the day of the appointment Dec 19th, 2000.
Dr. Gabriel Rodriguez, MD & Assistant Professor of Urology examines Mark & asked him to sign a consent form for photos. Off we go to the operating room where normally vasectomies are performed. I was allowed to be with Mark during the operation. After he was prepped (shaved & cleaned) they took photos of the sores. I didn't realize there where two spots. Dr. Rodriguez starts cutting, then tells Mark he has to go deeper into the tissue. Mark said he could see the surprised look on the Doc's face when he exclaims "It's alive"! He tells the attending nurse to get a container & drops the botfly larva into it. The nurse is checking it out when Mark tells him "I read on the internet that those things can jump 6 feet". He slams the lid on the container & sets it down! I pick it up & take it over to Mark. We watch this thing squirming as they close up the area it came out of & get ready for botfly  #2! This one is also alive & all we can think about is the movie Alien.

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This is a photo of the actual botfly larva removed from Mark.
Nasty looking critter isn't it?

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This is a close up of the spines.

This is a photo of it's mouth.

The photos were taken by Stephen Higgs, Ph.D. with the Department of Pathology at UTMB.

When Mark came back to the office (yes, he came straight to work) after the surgery he had a email from the WHO Collaborating Center for Tropical Diseases. It said "his email was read by a professor experienced in this area at UTMB & he suggested Mark visit any competent dermatologist for appropriate evaluation and management. In addition, from your (Mark's) email there is no indication that research is required or that the problem is necessarily botfly-related."
Boy was Mark mad. He emailed them back letting them know what he had just been through & ended it with........."The only Botfly larva survivor you will ever know!"
One day Mark commented on how uncomfortable the stitches were. I told him "well now you have a little knowledge of  what child birth is like". His reply was "Yes, but I had twins"!
Mark has healed & is now doing fine. We have been the joke of customers & friends that have heard about the incident. We even had a special poem written to the version of ''Twas the Night Before Christmas. Written by Bryan Springer.

The Mark Johnstone Version of ''Twas the Night Before Christmas"

''Twas the week before Christmas, and boy was it neat.
We had been on vacation, and my wife was in heat.
The doors were all bolted, the phone off the hook,
It was time for some nooky, by hook or by crook.
Momma in her teddy and I in the nude,
Had just hit the bedroom and reached for the lube.
When out from my privates there arose such a cry,
That I lost my boner and thought I would die.
Up to the window I sprang like a very big flea,
The pain was so bad it stung like a bee.
I ran down the hall past the 'putter I'd built,
And looked in a mirror, clean up to the hilt.
When what to my wondering eyes should appear,
But an airhole in my scrotum - I said to her....Dear.
With two holes now seen, half out of my sock,
It's time for a phone call, right now to a Doc.
The first one I called, said I'd just lost my mind.
So I paid him his worth ... it was only a dime.
The next one I called said it was just a small mite
Sure as I'm speaking, he was high as a kite
All I had left was to lay there in pain
A cry in the night with nothing to gain
Then down the chimney came a big red guy
St. Nick I told him, it must be a fly.
He was chubby and plump, a right jolly old prick,
And I laughed when I saw him, in spite of my dick.
A wink of his eye and a twist of his head
Soon gave me to know I had more problems to dread
Whoa Shithead he said - you are such a Putz,
Stop whining right now or I'll cut off your nuts.
A phone number he gave and a big bag of ice
He said call this Doc and he will be nice
He sprang up the chimney, to his team gave a whistle
And away they all flew like the down of a thistle.
But I heard him exclaim boy "Don't bitch or don't pout"
"Merry Christmas to all and be glad they are all out!"

Botfly Joke of the day!

Your Honor, his name was Johnstone.
I swear that I didn't know he was taking the kids out of the country

Video of a Botfly being removed from a girls head


The articles below were given to us by Dr. Rodriguez when Mark went in for his check-up.
Thank you Dr. Rodriguez & Dr. Rashid!



Michael Rashid, MD
Resident of Urology
The University of Texas Medical Branch at Galveston

Gabriel Rodriguez, MD
Assistant Professor of Urology
The University of Texas Medical Branch at Galveston

Cutaneous infestation by Bot Fly larvae, Dermatobia hominis, is endemic to tropical regions of Central and South America which typically victimizes small rodents and livestock. Because human myiasis is exceedingly rare even in endemic areas, correct diagnosis outside the endemic area is difficult because of unfamiliarity with the disease. Lesions produced by this insect are easily mistaken for cutaneous furunculosis. Though the disease is self-limited it commonly causes significant pain to it's victims. In humans,  early correct identification would avoid unnecessary treatment with antibiotics and allow earlier removal of larvae. To our knowledge, we present only the second case of scrotal myiasis caused by Dermatobia hominis in literature to date. The larvae were excised under local anesthesia with excellent results.
Case History:
48 Y/O WM presented to the urology clinic with complaints of "Pain in my scrotum". He describe the pain as intermittent, intense, and abrupt scrotal pain which began after recent travel to Costa Rica. He and his family had traveled to Costa Rica in late November to observe the Volcano Arenal eruption from the Los Lagos observatory. At night, while he was changing his clothes he felt a "mosquito" bite on his scrotum. He complained of immediate scrotal pain, which resolved quickly and without any signs of skin trauma.
Upon returning home he began noticing two"lumps" in his scrotal skin which would cause intermittent episodes of intense sharp shooting pain throughout his scrotum and perineum. Nearly four weeks from the initial bite, he noticed that these tow tiny lesions on his scrotum had "bloody discharge" but no signs of infection.
Two other physicians told him that his symptoms were related to a skin infection. He was placed on oral antibiotics for a presumed scrotal cellulitis and told to follow up in the urology clinic.
His scrotal exam was significant for two distinct furuncular lesions with a central pore. One located mid-raphae and the second on the right hemiscrotum. No fluctuance, however bloody discharge could easily be expressed with gentle pressure. The lesions measured approximately 1.5cm x 1.0cm
The patient had both lesions surgically excised revealing two live Human Botfly larvae. Pathology demonstrated infestation with fly larva (Myiasis) with inflammation, identified as Dermatobia Hominis.
Diagnosis of edemic tropical disease can prove difficult to physicians in other parts of the world. In this case of myiasis (parasitism by insect larvae), the patient developed painful lesions of the scrotum which were thought to be furuncles by other physicians.
In order Diptera family Cuterebridae, there are a number of fly species which utilize living mammals to incubate larvae. Parasitism of livestock and wildlife is common though human infestation with these species is usually accidental. However, one species does specifically target humans. Commonly known as the botfly or torsalos,
Dermatobia hominis is endemic to forest and jungle regions of Central and South America. Adult flies will capture other insects, such as mosquito's, and will lay eggs on them. These insects then act as vectors when they land on warm-blooded mammal. The larvae sense the increase in temperature and hatch. Once deposited, the larvae burrow into the subcutaneous tissue and grow for up to 6 weeks. Some species migrate through the host body to continue its growth at a separate location, but D. hominis does not migrate. At maturity, the larvae emerge, fall to the ground, and pupate into adult flies.1
Lesions produced by bot fly larvae often are mistaken for infectious lesions. 2,3,4 The initial penetration is usually painless and unnoticed by the patient. Infestation with multiple larvae is common. As the larvae grow, a subcutaneous mass becomes evident and the lesions are puritic. A pore, called a punctum, is present in the center of mass. The punctum is used for ventilation and excretion of waste. Seroganguinous fluid can be expressed and sudden paroxysmal episodes of sharp sever pain are usual. 3 On physical exam, the lesions seem to be non-tender. Without treatment, larvae emerge and lesions heal with good cosmetic result, however patients must endure painful episodes for up to 8 weeks.
Treatment involves removal of the entire larvae and may be achieved with several different methods described in the literature. Traditional tribal treatments include applying thick tree sap, raw meat, or animal fat to occlude the punctum and force the larvae out in search of air. This method of using occlusive dressings in combination with manual extraction has been described in the literature with success.4 However, attempts to extract larvae with traction run the risk of leaving fragments behind. Warm compresses or injecting lidocaine under the larvae also have been reported to force the parasites to the surface.3
Lesions in this case involved the scrotum. The patient attempted to lure the insects out by suffocation without success. Because of its redundancy, scrotal skin lesions are particularly amenable to surgical excision with good cosmetic result. Surgical excision of scrotal infestation may therefore be the treatment of choice.
  1. 1  Harwood RF and James MT. Entomology in Human and Animal Health. Macmillan Publishing.      1979.
  2. 2  Bowry R and Cottingham RL. Use of ultrasound to aid management of late presentation of Dermatobia hominis larva infestation. Journal of Accident and Emergency Medicine. 1997; 14:177-78.
  3. Johnston M and Dickinson G. An unexpected surprise in a common boil. Journal of Emergency Medicine. 1996; 14:179-781
  4. Gewirtzman A and Rabinovitz H. Botfly infestation (myiasis masquerading and furunculosis. Cutis. 1999; 63:71-72

Infectious Disease Pathology Conference
February 14, 2001
Case #1 (SP-00-17770)
Laura Chandler, Ph.D (Clinical Microbiology)
Gabriel Rodriguez, M.D. (Urologic Surgery)

Clinical Summary: This 48-year old male reported to UTMB with two painful lesions on the scrotum. He has no significant past medical history, but reported recent travel to Costa Rica. The lesions were examined and surgically removed.
Diagnosis: Myiasis due to infestation of the skin with Dermatobia hominis (human bot-fly).
Description: Myiasis is an invasion of tissues or organs by larval forms of insects in the order Diptera (true, two-winged flies). This order contains several families of medically important flies, including Sarcphagidae and Calliphoridae (screwworms and blow flies), Oestridae, Gasterophiliadae (botflies). Dermatobia hominis is in the family Cuterebridae and is referred to as the human botfly. The adult flies are 12-19 mm in size, with a yellowish head, dull blue-black thorax, and metallic looking abdomen. The legs are orange, and the wings are brown. This species readily infests several other species besides humans, including wild or domestic mammals, and birds. Infections in cattle and sheep can have significant economic effects
The life cycle of the botfly Dermatobia hominis is quite interesting because of the way in which the hosts become infected. Female flies do not deposit their eggs directly on the host. Rather , the adult female fly (after mating), actively seeks out biting arthropods such as ticks, mosquitoes , or other species of biting flies. The botfly captures the other arthropod, hold it's wings to prevent escape, and then attaches her eggs (roughly 15-30 at a time) on the abdomen of this other insect. The biting insect then carries around the botfly eggs. When this insect finds a suitable host for its own blood feeding, the botfly eggs are stimulated to hatch by the warmth of the host. A first-stage larva emerges from the egg and is deposited on the skin. The larva will burrow into the skin, either directly through intact skin, or through the bite from the insect vector. It can also enter through hair follicles or damaged areas. The burrowing process takes 5-60 minutes but apparently is not usually noticeable to the host.
The larva will develop at the site of entry, it does not migrate through the body although it does move around under the skin. It's anterior end is found towards the inside, and the posterior end is located at the skin surface. The anterior end is used to grasp host tissues for feeding. There are two oral hooks which are used for tearing tissue during the feeding process. The curved spines along the body assist with anchoring the larva in the skin. The larva is able to breathe through small spiracles located at it's posterior end, where the skin will remain open. The pattern of spiracles is one of the features used to differentiate the various species of botfly. The developmental stages take 4-14 weeks. The larva goes through two molts, to a 3rd instar stage, with emerges from the skin and drops to the ground. It pupates in the ground, taking 14-30 days to mature to an adult, which then emerges. Adult botflies do not feed, and live only a short time. The females are able to develop eggs because of the stored resources acquired from the host during larval development. Botflies are obligate parasites of vertebrates: their larvae must undergo development inside a warm-blooded host.
Epidemiology and Ecology: The distribution of Dermatobia hominis botfly includes Mexico, Central and South America. In the U.S., cases usually occur in travelers who have visited endemic areas. Flies live near water, thus coastal and forested or jungle areas are endemic for this species.
Clinical Manifestations: May depend on the location of the fly larva on the host's body. Usually larvae are found on the arms, legs, back and scalp. Other areas that have been reported are brain, eyelids, tongue, nose, genitalia and buttocks. Approximately 24 hours after infestation, a small (2-3 mm) papule will develop that resembles an insect bite. This will enlarge gradually to 10-35 mm and will be approximately 5-10 mm in height and will be surrounded by an area of induration. A breathing hole will be visible in the center of the lesion. As the larva develops, the lesions may become pruritic and produce a discharge that may be serous, serosanguineous or purulent. A secondary bacterial infection is actually uncommon. Often, pain (a stabbing feeling) is felt by the host; this is a result of the larva tearing off tissues while feeding, and from the spines irritating the tissues as the larva moves around. Usually systemic signs and symptoms do not occur, but occasionally malaise, letharge and insomnia have been reported.
Pathology: Moderate inflammation may occur in the area where the larva is found in the subcutaneous tissues. In general, secondary bacterial infections do not occur.
Diagnosis: Definitive diagnosis is made by removal of the larva followed by indenification by a medical entomologist or trained personnel. Tentative diagnosis can be made if there is a history of recent travel to an endemic area, and presence of non-healing lesions on the skin. The lesion may resemble other infections, so presence of the larva should be confirmed. Identification of the larva is relatively easy and is made by examining the spiracles, mouth hooks and pattern of spines on the body. Dermatobia hominis is easily distinguished from other botflies found in the Western Hemisphere, such as Gasterophilus spp. A similar fly, Cordylobia anthropophaga (also called the Tumbu fly), is found in Africa .Larvae are similar to Dermatobia hominis,but can be distinguished by the spines and spiracles.
Treatment: Removal of the larva. Larvae will migrate out of the skin if their spiracular plate is covered. A number of substances have been used to accomplish this, including nail polish, tape, wax, mineral oil, etc. The larva can be removed by grasping with forceps or applying pressure on both sides, but because of the curved spines, surgical excision may be required. Antibiotic treatment is not usually necessary and should only be used if a bacterial infection has developed.
Harrisons Internal Medicine online. Chapter 393, Ectoparasite Infestations and Arthropod Bites and Stings, Myiasis.
Kettle, D.S. Medical and Veterinary Entomology, 2nd Edition. CAB International, Cambridge, U.K. 1995. Chapters 14 and 15, pages 268-314).

So if you take a trip to Costa Rica or any other country that has botflys you are well informed!
And NOT ask to see Marks stitches!

I have composed a website with all the emails received over the years. These are from folks that have traveled from home only to find upon returning (home) they too have been a victim of a botfly!  If you would like to read these stories then just click on the (botfly) icon below.

  Click   Click here to read other stories regarding botflys to read more botfly stories and hear the Botfly Song!


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