While insects can indeed lay eggs in human bodies, it is not a common issue in the United States. It’s more prevalent in countries found in Central and South America where structures are less likely to be enclosed.
If you do suspect this is happening to you, you should reach out to a physician, rather than an entomologist.
Now, for the creepy details from Texas A&M AgriLife Extension Service senior program specialist Wizzie Brown.
It’s called myiasis
Myiasis is essentially an infestation of maggots. The insect involved is usually a type of fly.
The human botfly can directly affect people. Their range includes parts of Mexico and most of South America – which also helps explain why myiasis is more common there.
There is a rodent bot fly that is found in North America that typically hosts on rodents, like squirrels, or rabbits – but it can also affect humans. The same is true for horse bot flies and cattle bot flies, or warble flies (see “migratory myiasis” below).
Flesh flies are distributed around most parts of the world – including North America.
This squirrel is hosting larvae under its skin. (By Martin Bennett – Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=8272635)
The different types of myiasis
Furuncular myiasis
In these cases, Brown says an insect lays eggs on your skin and the eggs hatch out and the larvae burrow into your skin.
“And generally there you will get a red bump that kind of looks like a pimple or a boil or something. And a lot of times it’ll have an opening that is essentially the air hole for the insects to breathe in,” Brown said.
Another scenario is that insects have laid eggs on the foliage of plants, or on another insect like a mosquito.
“And when that mosquito comes and feeds on you, then you get the eggs on your body that way, or you brush up against foliage,” Brown said.
Migratory myiasis
This is where an animal has myiasis, usually horses or other equines, and the people get it from the infested animal.
With warble flies, which are typically found in cows, they usually die when they’re in human tissue – “because we’re not their primary host,” Brown said. So they can’t actually complete their cycle.
But, she said, some horse bot flies “can actually do their thing” in humans.
“And with horse bot flies, they can move under your skin up to 11 inches a day where they’re tunneling under your skin,” Brown said.
Intestinal myiasis
If somebody eats something with fly eggs on it, and if those eggs survive the stomach and the intestinal tract, they can actually hatch out as larvae.
As you might imagine, if that happens, the larvae might cause problems like abdominal pain, vomiting, and diarrhea.
Wound myiasis
That’s when flies are attracted to dead or dying tissue. If the wound is not being cared for, larvae can sometimes also move to other areas of the body.
“And usually that’s moist, soft areas,” Brown said. “So eyeballs, nostrils.”
The positive news
While even Brown admits this all is a little gross, she said there is a cool benefit. Doctors have come up with maggot therapy.
“So the Food and Drug Administration back in January of 2004, they approved the common green bottle fly to use as maggot therapy,” Brown said.
These maggots, she said, are grown under specific sterile conditions so they’re not introducing bacteria into the wound.
“But the cool thing about this, they are using these maggots essentially in wounds that won’t heal,” Brown said. “And they will put these maggots in there and they only eat the dead or dying tissue.”
While this therapy has only been approved by the FDA for a few decades, Brown says the benefits of what we now call maggot therapy has been in written records for over 5,000 years.
“So it’s been reported from the Renaissance times, one of Napoleon’s generals recognized that there were flies that ate only dead tissue, there’s records from the Civil War,” Brown said. “So this is one of those examples where we have looked into something that seems a little bit gross, and we have turned it to our advantage.”
Do you have a bug question for Wizzie Brown? Drop us a line, and we’ll pass it along.
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