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I stumbled upon a species I had never heard of before and... wow, what an intriguing species this is. This is a mosquito born vector that would freak anyone out. The species is (Dermatobia hominis) it is one of several species in which it's larva live as a parasite in it's host but the only one that is known to attack humans. The eggs will hatch immediately upon contact with the warm flesh of a mammal and the larva bore in to the skin to begin feeding until it is ready to pupate.
What I wonder is this... I have heard nearly everyone I talk to about spiders claim that either they, or a friend, or a friend of a friend, was bit by a Brown Recluse and had a really nasty necrotic wound. Brown Recluse do not live this far south, they are cold weather spiders, they are all over the place north of the panhandle, but certainly not in central Florida. After watching several of the video's on this fly, I am suspecting that people that think they have a necrotic spider bite, may indeed be hosting a bot fly. The wounds look similar and I would not be surprised if even a doctor would misdiagnose this event. once the larvae has buried itself inside the host, the only visible sign is a pimple like entrance wound that will not heal. The larva needs air, so it will keep the hole open and come up for air on occasion and then return deep within the tissue.
I read a very helpful article from an entomologist that had become a host during a field study. To remove the larvae, he covered the wound with petroleum jelly to force the larva to surface for air, then he could grab the larva for removal. It is important NOT TO PULL the larva if you ever become host. They have backward facing barbs on their skin, similar to a bee stinger that helps prevent it from being pulled out. The technique is to let the wiggling action of the larvae do the work to free the barbs, pull with a steady but gentle force and let it wiggle it's way out.
Here is a link to one of the You Tube Videos, they seem to be fairly reasonable people with a genuine interest in science, listen to the comments and observations, they are obviously quite familiar with the species.
www.youtube.com/watch
What I wonder is this... I have heard nearly everyone I talk to about spiders claim that either they, or a friend, or a friend of a friend, was bit by a Brown Recluse and had a really nasty necrotic wound. Brown Recluse do not live this far south, they are cold weather spiders, they are all over the place north of the panhandle, but certainly not in central Florida. After watching several of the video's on this fly, I am suspecting that people that think they have a necrotic spider bite, may indeed be hosting a bot fly. The wounds look similar and I would not be surprised if even a doctor would misdiagnose this event. once the larvae has buried itself inside the host, the only visible sign is a pimple like entrance wound that will not heal. The larva needs air, so it will keep the hole open and come up for air on occasion and then return deep within the tissue.
I read a very helpful article from an entomologist that had become a host during a field study. To remove the larvae, he covered the wound with petroleum jelly to force the larva to surface for air, then he could grab the larva for removal. It is important NOT TO PULL the larva if you ever become host. They have backward facing barbs on their skin, similar to a bee stinger that helps prevent it from being pulled out. The technique is to let the wiggling action of the larvae do the work to free the barbs, pull with a steady but gentle force and let it wiggle it's way out.
Here is a link to one of the You Tube Videos, they seem to be fairly reasonable people with a genuine interest in science, listen to the comments and observations, they are obviously quite familiar with the species.
www.youtube.com/watch
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Re: Bot Fly
Wed, July 9, 2008 - 12:08 PMvery interesting Sean...and I wouldn't want to become a host for this beast!
We have hobo spiders up here in Western Canada that can cause a necrotic wound...luckily they are not aggressive individuals! -
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Re: Bot Fly
Wed, July 9, 2008 - 10:07 PMWe do not have the Hobo Spider in Florida, but we do have four species of Widow Spiders (Latrodectus). I have heard of the Hobo, I have caught and studied other funnel web spider relatives when I lived in California. The Widows are not aggressive in Florida either. I have been bit twice by something unidentified that caused a necrotic wound, I never found the creature that bit me in my sleep. I know it was not the Brown Recluse (Loxosceles), they do not live in central Florida, and it could not have been the Hobo Spider (Tegenaria agrestis), they are a Northern Spider. I do not think Widows cause necrotic wounds, they have a neurotoxin venom. I believe mine was from a Yellow Sac Spider. Whatever bit me caused a wound that continued to fester for 6 months, and to this day there is a cavity in my earlobe that collects junk I have to squeeze out every 6 months or so. Fortunately, we do not have this species of Bot Fly in Florida, we have a relative of it that attacks the squirrels but there are no confirmed incidences that I know of that include a Human host for these flies. -
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Re: Bot Fly
Thu, July 10, 2008 - 2:25 PMI've actually seen a bot fly larva! It's a fascinating and utterly creepy thing to watch the extraction of a living one from a host. I was volunteering at the Morse Ranch wildlife rehabilitation center in Eugene, Oregon, and a caring gentleman dropped off a chipmunk that he'd found. It was very lethargic and sickly, and the reason was the fly larva. The larva itself was very large compared to the wee little chipmunk and I think the chipmunk would have died had the larva stayed in it many more days longer.
My question would be, does the larva secrete some sort of numbing fluid? How would a host not feel it burrowing? -
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Re: Bot Fly
Fri, July 11, 2008 - 10:52 PMI am not sure if the larva secretes an antiseptic or not. My suspicion is that it does, all the research I have done indicates that it's infestation is painless, at least in humans. When I consider the similarities in mammalian hosts (humans vs. rodents) I have to conclude that the reports of painlessness from human samples would be universal to all mammals. I do not think the chipmunk, or squirell , common in Florida, feel any pain from this parasite. The lethargic and sickly condition of your chipmunk could have been a result of parasitic anemia, but that is a far fetched notion when survival of the fittest is considered. The parasite relies on the health of the host to survive, if the function of the parasite were to include a deprivation of essential minerals and nutrition, the parasite would contribute to it's own death. I conclude that your specimen you have is suffering more than a parasitic occupancy of this fly larvae. It could well be a secondary infection that is robbing this mammal of the nutrients necessary for optimal health. can you do a iron scan to determine if the animal is suffering from anemia that could be caused by a parasitic guest? -
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Re: Bot Fly
Mon, July 14, 2008 - 2:28 PMHi Sean,
I would love to enlighten you on the possible secondary effects the little guy was suffering, but this was a lot of years ago, and at the time, I don't think I was nearly so curious about it. I remember it was quite a large larva compared to the small chipmunk; the vet extracted it in exactly the way described above, with a slow steady pressure, and I was shocked at how large it was once it was out. He said it was a bot fly, but are there other species that burrow in the same way?
What you say makes sense in that it doesn't seem as if the larva could have much success without a healthy host and in the end, there could have been any number of things wrong with the chipmunk in addition to the parasite. It's a bummer that I can't recall. :( -
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Re: Bot Fly
Tue, July 15, 2008 - 12:16 AMBaya,
I do not believe there are other species in Florida that do this, but I am really not sure and have not researched it. I wonder what defenses our human skin, devoid of fur, provide to protect us from these things. Think about it! that little larvae has to make it through ALOT of fur to even get to the skin, it just seems like we would be an easier host, but somehow, evolution has dictated otherwise. I wonder if it is diet? perhaps the larva need nutrients only found in herbivores? they love Squirrels, but rarely Humans, Cats, or Dogs that are in the same area. -
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Re: Bot Fly
Sat, July 19, 2008 - 7:55 PMI've heard of several accounts of bot fly infestation in humans, but they were all from Central or South America and second hand. I've seen pictures of the effects though, and it is really nasty. Have also seen a confirmed recluse bite and aside from the necrotic tissue, there didn't seem to be enough similarity to mistake one for the other, but I suppose it depends on the severity of the bite and the reaction the host has to the parasite... -
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Re: Bot Fly
Sun, July 20, 2008 - 11:16 PMI thought the stills were bad. The videos are way more disgusting. In that trainwreck can't-look-away sort of fashion. I love insects man, but parasites still give me the willies. -
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LOL@Maevrin
Wed, July 23, 2008 - 11:58 PMYes ,.. I agree, human parasites are kinda creepy. From what I have read, they are not really dangerous, they do hurt a little because of the spikes they grow to stay inside,.. but... this is nature at it's finest, even at the top of the food chain, we humans are nowhere close to parasitic immunity. The bot fly is just an extreme example of the human parasite, we live with many more unknowingly.
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Re: Bot Fly
Wed, July 23, 2008 - 11:55 PMWhere did you see a confirmed recluse bite? I am interested in learning how the doctor or whoever confirmed the bite could determine the species from the wound. -
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Re: Bot Fly
Sun, July 27, 2008 - 8:10 PMSean: The species was determined in the lab as they had the spider responsible for the bite.. As far as I know there really isn't a great way to determine species from the bite other than biogeography and the type of tissue damage and reaction. Every person reacts differently, so it's hard to be sure without the actual specimen. -
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Re: Bot Fly
Sun, July 27, 2008 - 10:50 PMMaevrin,
I agree, a necrotic wound is fairly prominent, there are only a handful at best that can produce a necrotic wound in Florida. Most of the danger is in secondary infection. Our most dangerous spider, Latrodectus (widow) does not produce a necrotic wound. I have never seen a necrotic wound in person, only pictures on the internet, my proposition of a Bot Fly resembling a necrotic wound is not authoritative. I just think, based on the pictures, that an early bot fly invasion looks very similar to a necrotic wound, it leaves a large cavity that is susceptible to secondary infections. In the lab, I would suspect the chemical components of the venom could be determined. We have made tremendous strides in DNA structure and Protein structure. I don't know what the half life of spider venom is, but if there are any traces if it in the wound, I would think that a positive identification of the species would be possible if the patient could afford such tests.
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