Volcano Arenal
Volcano Arenal, La Fortuna, Costa Rica

While viewing the very active volcano Arenal in the small town of La Fortuna in Costa Rica, Mark Johnstone was bitten by a mosquito. This happened on the evening of November 24th, 2000, in the viewing area of Los Lagos.

Let the story begin…

Upon returning home from Costa Rica, Mark started to experience a strange pain in his scrotum. He finally mentioned it to me (his wife, Brenda Johnstone) and we talked about what it could be. Spider bite? Infected mosquito bite? Then I remembered 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 larva – 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 tidbit 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 and 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. Well, remember that this was back in the year 2000, and the internet was not nearly as resourcefull as it is today. We finally found a few websites that confirmed, at least in our minds, that a botfly was the culprit.

One Bad Botfly

The pain was not like the book described. Mark was getting bitten at random times. Mostly when he tried to sleep and different times at work. Apparently, every time the botfly larvae would move around or need to eat. it would send shooting pains throughout his body. He described it as a spiking, jolting pain as though you had stuck your finger in an electric outlet. Problem was, it was not his finger! Since he is a great bearer of pain he decided to call UTMB (University of Texas Medical Branch in Galveston, Texas) 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 Dr’s appointment with our general Doc. This Doctor decided that Mark must have lice and gave him lice medicine. Meanwhile the botfly’s got bigger and bigger as they feasted upon his scrotal tissue. The painful biting episodes became worse and happened more frequently. 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 Lagos Observatory where Mark was bitten by the Botfly carrying mosquito.

Volcano Arenal
You can see the clouds clearing off the top of Volcano Arenal as Mark (on the right) and Wendy watch it erupt. During the day you could see the lava smoke coming down, but at night it was a spectacular show of glowing red/orange lava. A great place for a human botfly to hang out, right.. . . .
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 Lagos closed their 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 Christmas season and 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 and 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 and where he had heard about botflys. He told us that he heard about them on the Discovery Channel but didn’t know much. Wish he had been a doctor!

After being escorted down the hall to our examining room, I watched at the door as Mark laid on the examining table totally depressed. One lady doctor picked up Marks chart and said “I’m not touching that”!  Hours later a Doctor arrives and we tell him the story. He asked us “What other DR’s are you seeing and are you on any kind of medication?” He then tells us he has to call in a urologist. Meanwhile he goes to a computer in the hall and types in “botfly”.  I sneak up behind him and say…. “there is a lot more information on the net if you want me to show you where it is! He turned to me in surprise and 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. He 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 and Assistant Professor of Urology examines Mark and asks 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 entire operation. After he was prepped (shaved & cleaned) they took photos of the sores. I didn’t realize there where two spots. He was then given a local anesthetic in his scrotum. Yes, that’s right, “excuse me while I stick this needle in your family jewels…”.  Ouch!

So now, Mark Johnstone is wide awake laying on the operating table, with a pillow propping up his head, so as to get a direct view of the doctors and three or four nurses as they begin to cut into his scrotum. His wife, Brenda Johnstone, is standing behind his head, holding his hand for moral support.

Mark will now tell more of the story from his own perspective…
Just picture this if you can. Just staring and waiting and enduring and waiting. Why, only two hours ago, we were watching a beautiful sunrise on our deck drinking coffee. After what seemed like forever, but was probably only 15 minutes, my patience was wearing thin, and my mind was thinking the worst. I experienced a very painful episode around 4 AM this morning. My botflys were in a feeding frenzy munching down on my scrotal tissue. It was terrible piercing pain. Now, I began to wonder if perhaps they had hatched and were flying around in my bedroom. The doctor has been digging in my scrotum to no avail. Now exasperated, I ask the doctor if he as found anything yet. “No Mark, nothing yet, we will have to cut deeper into the tissue”, he replies. Only a few minutes later, I am staring at the doctor when he get’s this weird look on his face and his eyes are as big as saucers. He exclaims “It’s alive!”.  He tells the attending nurse to get a container and drops the botfly larva into it. The nurse is checking it out when I tell him “I read on the internet that those things can jump 6 feet”. He slams the lid on the container and sets it down! Brenda picks it up and brings it over to me. With tears of joy, we now watch this thing squirming as they close up the area it came out of and get ready to search for botfly number two! They finally locate him and remove him. He too, is alive. The room now has a completely different atmosphere. As though everyone in it is bewildered at what just took place. It reminds me of that famous scene from the movie “Alien”. My nightmare is now over.

Brenda will now pick up the story again…

Photos of the actual human botfly larvae extracted from the scrotum of Mark Johnstone


human botfly larva
This is a photo of one of the actual human botfly larvae removed from Mark’s scrotum Nasty looking critter isn’t it? All photos were taken by Stephen Higgs, Ph.D., with the department of Pathology at UTMB.
human botfly larva removed from scrotum
This is a closeup of the spines. No wonder it hurt so much when they moved.
human botfly larva
This is a closeup of the botfly larva’s mouth. I guess he had fun munching my scrotum!

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 whom 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 and ended it with………”The only scrotal Human 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 and is now doing fine. We have been the joke of customers and friends that have heard about the incident.

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