Human Botfly (Dermatobia hominis).
Illustration: Arthur Cushman (Wikimedia Commons).
Will was a short man, energetic, sanguine, and perfectly at home in the jungle. It was obvious he loved being there, and equally, he loved to swing his thin machete, slashing at vines and branches with an insouciant deftness. I'd been walking with this Belizean samurai for an hour along a sun dappled rainforest trail where he'd been given me a crash course in jungle survival skills: preparation of medicinal plants, simple tricks for tracking and catching prey without a weapon, how to suture wounds shut with leaf-cutter ant jaws - you know, the usual everyday stuff a rainforest walker should know. We drank deliciously pure water from a thick vine; we tracked a Lowland Paca (Cuniculus paca) to its burrow; we feasted on handfuls of tiny lemony-tasting termites.
Through riotous green tangles of leaves and fronds we walked, stopping every so often for another improptu botany lesson. Learning tropical botany is an immense affair, and the helping hand of a guide such as Will, whose life has been closely tied to the rainforest was tremendously helpful. We bushwacked our way up a small hill to look at a Fishtail Palm (Chamaedorea ernestiaugusti), a highly sought-after and increasingly rare species, that is collected (often illegally) from the Belizean rainforests and sent all over the world to be used as components in flower arrangements - a miserable use of such a rapidly declining species. We cracked open Cohune Palm (Attalea cohune) nuts. We fashioned plates and bowls out of leaves. We tasted the bitter bark of one medicinal tree after another and learned how to cure seemingly almost every common ailment you could imagine.
I couldn't keep up with my note taking, there was just too much to record, so I just walked and listened as Will lead me through a claustrophobia of trunks, stems and lianas, across shallow creeks, and along the same trails that Jaguars (Panthera onca) and Ocelots (Leopardus pardalis) had left there tracks upon only hours before us. Will compared the culinary merits of various small game: Great Curassow (Crax rubra) was excellent but hard to come by, while Crested Guan (Penelope purpurascens), though more common, was far too gamey; Nine-banded Armadillo (Dasypus novemcinctus), he derided saying that only a bad hunter would eat such a thing, but Central American Agouti (Dasyprocta punctata), now that fat little rodent was a delicious treat. He said he was a good enough shot to kill a Baird's Tapir (Tapirus bairdii) with a .22 caliber riffle; I said he was full of shit.
Though we talked incessantly about animals, we actually saw very few. (Perhaps it was our incessant talking that kept them away). The rainforest was eerily silent. Once in a while came the mellow winnowing of a distant Little Tinamou (Crypturellus soui) or the undulating song of a Spot-breasted Wren (Pheugopedius maculipectus), but for much of the morning we walked in a quietude that seemed terribly out of place in a habitat so blessedly verdin. It's a strange little paradox of the rainforest: animal life is abundant, but it can be frustratingly hard to observe. Sometimes though, the wildlife comes right to you. And come to me it did, in the most audacious way that it possibly may: as an endoparasite.
It wasn't on my walk with Will that I acquired my parasite, or rather parasites, but it was all-knowing Will who was able to confirm my suspicion: I had been infected by not one, but two Human Botflies (Dermatobia hominis). No problem said Will, follow me. A little way down the trail, he began chipping away at a tree trunk with his machete. I wondered what pungent plant I was about to sample this time. But instead, Will gathered a mass of sticky latex sap from the wound he chiselled in the trunk. Urging me closer he dabbed a bit of latex on each of the small lesions that had formed around the two week old botfly larvae anchored in my forearm.
The sticky tree sap was from a whimsically named species, Horse's Balls (Tabernaemontana donnell-smithii), whose fruit, Will earnestly assured, looks just like equine testicles. What a marvellous life moment! To be standing deep in the silent rainforest, my arm smeared with the sticky goo of a tree called Horse's Balls and two little parasites writhing around under my skin; talk about becoming one with nature!
My affair with the botflies began about two and half weeks earlier when I was camped in the Cockscomb Basin. It was there, perhaps on only my second day in Belize, that I was parasitized in a most clandestine manner. I would probably have noticed had a female botfly lain her eggs directly on me, after all, an adult botfly is about the same size as a honeybee. But adult Human Botflies are seldom seen by non-entomologists, and they don't lay their eggs directly on people or other hosts - dogs, monkeys and deer are probably more common hosts than are humans. No, Human Botflies have a more roundabout and rather unconventional means of getting inside you or your pet dog: they enlist the services of another devilish insect, the mosquito.
As if mosquitos weren't bad enough with their potential to carry a cadre of nefarious aliments such as malaria, chikungunya, dengue, yellow fever, Rift Valley fever, equine encephalitises, Japanese encephalitis, La Crosse encephalitis, St. Louis encephalitis, and West Nile virus, they are also a botfly taxi service. Female Human Botflies have the remarkable ability to capture live mosquitos in flight. With a mosquito in hand, as it were, the botfly deposits one or more eggs, before releasing her curior unharmed. Apparently, botflies are not particularly picky when it comes to choosing a mosquito species, dozens have been recorded as vectors (a few species of non-mosquito vectors have also been reported). But botflies only take female mosquitos, because they, and not the males, seek out blood meals from mammalian hosts that botflies ultimately want to infect.
The newly liberated, paratenic porter goes about her sanguinary mission to obtain mammal blood with which she will nourish her own eggs. As soon as the mosquito touches down, on say a naturalist's arm, the botfly eggs, triggered by body heat, hatch with amazing rapidity. The larvae then drop onto their new host's skin. In time, the maggot, indeed it is a maggot - as if we needed to increase the gross-out factor - works it's way down a hair follicle or maybe even through the mosquito bite wound. Once under the skin, the real fun begins.
Myiasis (the medical term for a maggoty infection) goes beyond the Human Botfly and can be caused by a frightful pantheon of other species. Among the most economically important is the Sheep Blow Fly (Lucilia cuprina), which can cause significant losses for wool and mutton producers. Attracked to feces- and urine-tainted fur, the blow fly larvae often develop on their hosts' anaus, where the lesions can turn dangerously septic. Then there is the Sheep Botfly (Oestrus ovis), a marvellously insidious beast, that shoots its eggs directly into their host's nostrils, including sheep (of course), other livestock, deer, and apparently the occasional human. The Sheep Botfly larvae, when it hatches, crawls further into the nasal cavity, where it feeds on tissues and bodily fluids, no doubt to the intense irritation of the host, before being sneezed out to complete its pupal stage underground. Similarly, in the far north, the prodigious maggots of Hypoderma tarandi ravage the nasal cavities of Caribou (Rangifer tarandus). Female ox warbler flies (Hypoderma spp.) lay their eggs on the forelegs of livestock and wild ungulates. The eggs are accidentally ingested by the cow or elk or bison when the host licks itself. But the stomach is not the place Hypoderma wants to be. The larvae migrates through the cattle's muscle tissue, sometimes causing a significant damage, until it finds its way to the skin's underside, where it sets up shop. The equine botflies (Gasterophilus spp.), take a much simpler approach, laying eggs by the dozen or by the hundred directly on a horse or a donkey. There are others: the rodent and rabbit botflies (Cuterebra spp.), and the Congo Floor Maggot (Auchmeromyia senegalensis), which infects burrowing wild pigs, Warthogs (Phacochoerus africanus), Aardvarks (Orycteropus afer), and hyenas. To be sure, there are also a few species with a particular (though not exclusive) taste for human flesh. There are the screw flies (Cochliomyia and Chrysomya ssp.), which typically infest exposed wounds on humans (and livestock), but will also feed on healthy living tissue. In the case of the Cochliomyia, it has been the focus of ongoing biological warfare. Cochliomyia has more or less been eliminated from North and Central America through an extensive programme of releasing sterile males into the wilds of Panama to prevent the recolonization of Central America by flies dispersing northward from Columbia. In central Africa lives the Tumbu Fly (Cordylobia anthropophaga), another habitual human parasite. The scientific species name says it all; it translates as "human-eater". The female Tumbu Fly lays her eggs on soil, when those eggs hatch, the larvae crawl onto bare-footed humans or other mammalian hosts. The rest of it's life cycle is similar to it's New World counterpart, the Human Botfly.
Human Botfly development is an intriguing thing, and the only way to fully appreciate it is to become a host yourself. Disgusting as that may sound to the average person, I assure you that there are a great many folks out there (most of whom study insects for a living), that would happily rear a botfly to full term. It's been a running joke among my travelling companions, that should one of us become infected by a botfly, that we'd certainly see it through to adulthood. That says something about my friends, I suppose. But let's face it, Human Botflies, however off-putting their life cycle might be, are undeniably interesting! So here I was, with two of these little maggots lodged in my arm, deciding what to do. To raise them, or not to raise them. In the end I decided not to raise them. The decision, a seriously considered one, was made for two reasons. First, I had a girlfriend, and I wanted to keep it that way. I mean, a guy who honestly considers rearing a couple of botflies out of his forearm doesn't get a lot of chances with cute girls. The second reason was simply because the little buggers were uncomfortable most of the time, or downright painful on occasion - that helped wear away the novelty. But, I didn't take them out right away. After all, I was busy, chasing Belizean birds and opossums and lizards, all day and all night; I'd spend a few days, I decided, getting to know what it really meant to be parasitized.
It wasn't until about one week after I was infected that I began to really notice the myiasis. The lesion that each larvae created was like a small pimple with a pore at its centre. The lesions grew considerably during the first week; indeed, it sort of looked like I'd suddenly developed two nipples on my arm. The central pore was where the maggot's breathing snorkel, its anal spiracle, came to the skin's surface. The pore also exuded a slight but near continuous trickle of fluids, sometimes bloody, sometimes clear. And as the maggot grew and shed its outer skin, that too was ejected from the pore. If I looked closely, I could see the breathing tube move up and down, as the insect was respiring and pumping out waste juices. The maggots, when left for a full term may take anywhere from six weeks to a couple of months to mature. Once fully satiated on human body fluids, the larvae turns around, wiggles out of the pore, falls to the ground, digs into the soil, and pupates for another few weeks or months. My maggots never made it that far.
Will's trick with the Horse's Balls sap didn't work on the day of our jungle trek; I had accidentally brushed it off by the end of the walk, and I'd be damned if I could find my own Horse's Balls tree to replenish among the dozens of other similar looking species. I was likely to accidentally smear some kind of dermetetic sap on my arm instead. Without much care, I decided to just go about the rest of my trip, another two weeks, with those dastardly little hitchhikers inside my forearm; I'd take care of them when I returned home to Canada. So the maggots got a good tour of Belize and neighbouring Guatemala. They snorkelled on some of the most wonderfully diverse reefs anywhere on Earth. They were there when an Ocelot came to my campsite one night. They clamoured up and down ancient Mayan ruins. They got a good dose of the local brew, Belikin Stout, on more than one occasion. They even experienced a few days of breathtaking Canadian prairie cold when the three of us (my botflies and me) returned to Canada. But finally I grew tired of my little friends waking me up in the middle of the night with their incessant squirming. I could feel them readjusting the dozens of tiny carotenized spines that surround their bodies, like miniature crowns of thorns. Those spines are there to keep the maggots anchored in place. They make it so the bugs can't be readily squeezed out through passive mussel action or by directed effort - believe me I tried. I was also tired of my arm oozing like a dripping faucet. So how to get them out?
There are endless folk remedies for removing botflies, aside from utilizing Horse's Balls sap. I settled on the one that Will suggested to me as an alternative to his jungle therapy. I simply placed a piece of tape over each lesion for a day or so to smother the maggot, causing it to relax its spines, and back part way out of its organic burrow in search of oxygen. I could then pull them out with forceps. I used a piece of clear Scotch tape so I could monitor the situation. Sure enough it worked. After about six hours of suffocation I had the little guys out of me with only a minimum amount of pain as their bulbous bodies squeezed through the tiny breathing pore.
Looking at the larvae up close, each about 1.5 cm long, I could see the rings of black backwards pointing spines and the circular mouth. It's the only working mouth that the botflies will ever have. As adults, they don't feed. They don't sip nectar as some biting flies do. The females don't require a blood meal to get her eggs developing. The 2-6 day life of an adult Human Botfly is fuelled solely by the nutrients that it manages to suck out of its host as a larvae. The life of a male adult Human Botfly is perhaps best described as nothing more than gene transport. A male finds a female, mates with her, and perhaps one or two others, and then dies. Females, after having mated once, go about their clever mosquito catching until all of their eggs have been thus dispersed.
In the end there was no infection, no scars, no mental trauma, just a wonderfully morbid memory of the Belizean rainforest.
