Bot Fly Larvae Are My Zebras

April 20, 2011

Photo of Patrick Mahaney Bot Fly Larva Open MouthDuring veterinary school, there are many illnesses about which we burgeoning doctors are educated. Many are common diseases which we face in clinical practice on a regular basis. Others are less common and are given the nickname “zebras”. I just treated one of these zebras in the form of bot fly (Dermatobia Hominisor) larvae removal from a dog in Peru. Those having seen Animal Planet’s Monsters Inside Me may know of the gut wrenching horror caused to humans harboring these arthropod beasties.

One of the remote locations I worked at during my vets abroad Peruvian trip with Amazon Cares was the village of San Pedro on the Amazon River. This quaint and tidy location was a pleasant change from the crowded filth of Iquitos. Friendly people inhabited both places, yet the San Pedro natives better respected their surroundings, which reflected in the overall cleanliness of their buildings and grounds.

As the dogs and cats of San Pedro live a more rural existence in the jungle, the volume of external parasites I was called upon to treat was considerably higher than their city counterparts. The poor dogs and cats were covered with fleas, which also seemed to have an appetite for our gringo blood.

Photo of Bot Fly Larva Black Dog
A few of the dogs harbored bot fly larvae under the surface of their skin. The firm nodules in the subcutaneous space, termed warbles, are relatively easy to locate and occur after the bot fly larvae enter the skin.

My surgery patients were anesthetized for spay and neuter procedures, so I was able to remove the larvae with relative ease while causing no apparent discomfort. With gentle persistence and retraction, out popped an appalling caterpillar-esque parasite that otherwise would have hatched and burst forward into the world to repeat the process on another creature (including humans).

Photo of Bot fly larve green surgical towel

Besides the shocking photos, some amazing video was shot vividly detailing the larvae removal. Unfortunately, due to the speed of video upload, I will have to post these stomach churning videos when I am back in the states (so make sure to sign up for email delivery of my blog by following this link).

Besides living in an environment free from bot fly inhabitation, the best thing to avoid having bot fly eggs implanted in your pet’s skin is to prevent insect bites from happening in the first place.

Photo of Myiasis Life Cycle Bot Fly CDC

Interestingly, the lifecycle (see Centers for Disease Control Myasis chart) of the bot fly requires an arthropod vector, such as a mosquito or tick. The vector carries and releases the bot fly eggs onto an animal’s skin which hatch into larvae which enter the body through any readily available opening. Even holes from insect bites, cuts, abrasions, or any other skin trauma can potentially act as the larval portal.

If you live in a bot fly infested environment, which is common around farms housing livestock, employ regular deworming to kill ingested larvae that may pass out with feces and hatch into adults.

For dogs, topical insect repellant, such as those that contain Fipronil (Frontline) or collars impregnated with Amitraz can help. I used Fipronil to kill many ectoparasites, including fleas, ticks, but not adult bot flies. Externally located eggs and larvae that contact the product on a pet’s skin or coat will die. Unfortunately, after the eggs have been implanted, there is no proven reliable treatment besides surgically extracting the more mature larvae. Prevention is key!

So, use such a product if your pet could be exposed to any biting pests. Make sure to use a product that is appropriate for your pet’s species (cat product on cat, etc) and follow the recommend dosing guidelines as per your veterinarian.

Natural products, such as those containing plant derived oils (cedar, chrysanthemum, etc) can also help deter bug bites, yet may not be as effective and could make your pet sick if used improperly. The same applies for manufactured products, so only use only on healthy pets under veterinary supervision.

I have a few more days of work in Peru and more remote villages on the Amazon River at which I will be treating people’s pets. I imagine more opportunities to treat bot fly larval infestations, which is my zebra condition, will manifest.

Thank you for reading my article and to my friend Dr Jessica Vogelsang (AKA Dr V of the excellent blog for taking such fabulous pictures.

Make sure to follow my Amazon Cares adventures by friending Patrick Mahaney: Veterinarian Acupuncture Pain Management for Your Pets on Facebook and @PatrickMahaney on Twitter.

{ 12 comments… read them below or add one }

Dr V April 21, 2011 at 4:55 PM

This is such a great post. Now I know what to do with all the botflies I am certain are infesting me. 😀

Patrick Mahaney April 22, 2011 at 12:57 PM

Thx Dr V. We both were able to reach our gross out quotient for the week via bot fly larvae!

Bev April 22, 2011 at 4:02 PM

You are both amazing! And I am now squirming in reaction.

Patrick Mahaney April 22, 2011 at 6:12 PM

Hi Bev,
Thank you so much for your comments. Both Dr V and I are now quite proficient in removing bit flies from our patients, which is great considering that it is otherwise a rarity in our San Diego and West Hollywood (respectively) practices.
Follow for more Peru vets abroad articles!

Patrick Mahaney May 15, 2011 at 2:08 PM

Thank you Reagan.
Bot fly larval infestations are nasty happenings for any organism suffering from the infestation!
I hope to see you again! Sign up for email delivery of my blog posts by pressing the large, orange “Don’t Miss A Blog Post” button on my site.

Patrick Mahaney May 15, 2011 at 2:08 PM

Thank you for your comment. I like to share some of the crazy experiences I have in my veterinary career!

Sheila August 5, 2011 at 10:10 AM

My goat has a nodule under her jaw on her neck. I was told to check it for bot fly. How can I tell if it is a bot fly and how do I get rid of it?

Patrick Mahaney August 6, 2011 at 8:22 AM

Thank you for your comments.
A bot fly “warble” should have a small opening to the surface of the skin through which the bot fly larvae can get oxygen and erupt through the surface when the time is right.
As bot fly infested environments are common around farms housing livestock, regular deworming kills ingested larvae that may pass out with feces and hatch into adults. Additionally, prevention and treatment of parasite infestation are vital, as manual removal of larvae is the only reliable treatment.
Can you send a photo to ??

Margaret June 27, 2012 at 4:56 PM

I removed a botfly larva today from my dog in Western Nebraska- Likely the kind with rabbit hosts since I have had many rabbits in my yard. I placed Neosporin over the breathing hole and held tape for 5 minutes to get it to crawl out.
I am thoroughly grossed out by this whole experience. The dog looks very happy (now).

Patrick Mahaney June 27, 2012 at 11:34 PM

Thank you for sharing your story about removing a bot fly. They are things of nightmares, for sure.
Check out my video (part 3) of bot fly removal:

Bonnie Dalzell August 14, 2017 at 7:45 AM

When I was taking a mammalogy course in college in California (1968) I was doing a museum prep with a dead cotton tail rabbit and when I was skinning it suddenly there was a flurry of motion under the skin and out popped a large white maggot with sparse hairs on it. Gave me a real start (Zombie Rabbit?). It was in the days before cell phones so I did not get a photo. Took a bit of research to figure out it was a bot fly larva in those days before the internet.

Patrick Mahaney February 10, 2018 at 2:04 PM

Great story! If only you had the picture (or video).
Thank you for your comments.
Dr. PM

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