Deer Flies and Lyme's Disease

circa1825March 5, 2007

I just wanted to warn people about deer flies being a vector for Lyme's Disease. Last year, a deer fly landed just below my ankle. I smacked it with my hand and was pretty happy that I'd gotten it before it bit me. At some point after that, the spot where it had landed started to swell up until I couldn't see my ankle, and the spot turned red, then purple, and then black. I thought maybe the deer fly had bitten me after all and I was allergic to it, just like I am to anything that stings.

I started reading about deer flies and found out that people can get Tularemia from deer flies. Tularemia (deer fly fever) is a bacterial infection and is actually on the government's "watch list" for bioterrorism. Between that and the fact that I was already concerned that my foot might be rotting off, I went to the doctor. She took pictures of my foot, drew a circle directly on my foot around the area so I could monitor its spread, put me on anti-biotics (in case it was Tularemia and also because she saw that one of my ears was red inside), and sent me out to get tested for Lyme's Disease and bacteria. The test came back negative. Things got worse after a few days, so she put me on Prednisone. When things continued to get worse, she had me tested again. This time the test was positive for Lyme's and I got put back on anti-biotics. Apparently there is about a two-week window where Lyme's may or may not show up after a person has been bitten.

I learned that getting Lyme's from a deer fly is much more rare than getting it from a tick, but something I saw on the Internet said that CT, RI, NY, NJ, PA, MD, WI, and MN account for 92% of cases of Lyme's. On top of that, Nantucket County, MA was the highest in 1999 with almost 1 in 100 people contracting the disease that year. I live in south central MA, so just beware.

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claireplymouth z6b coastal MA


I did a quick Google and found a reference to a report in the New England Journal of Medicine in 1990 concerning a similar case, but there were very few other notes.

On general principles, I just revised the FAQ to include your experience, in case it helps other people.


Here is a link that might be useful: Revised FAQ on Lyme Disease

    Bookmark   March 5, 2007 at 5:49PM
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Wow, it's certainly a good thing that both you and your doctor were paying attention. I don't think that you know for sure that you got Lyme disease from the deer fly, especially since it didn't bite you. It doesn't sound like the bruise was a bullseye, but that doesn't mean that it was unrelated to the Lyme (or otherwise).

In any case, it made me curious, and I did a quick google to check out the deer fly Lyme connection. One site, at OSU, says "Also, deer and horse flies are suspected of transmitting Lyme disease (New England Journal of Medicine 322:1752, 1990)."

Another site,, said "One case of Lyme disease from a horsefly or deer fly bite was written up in the New England Journal of Medicine in 1990, but the Centers for Disease Control (CDC) does not believe that the disease is transmitted by flies, fleas, or mosquitoes."

I found the issue of the NEJM on the web, and this item is in the "correspondence" section, so it's not a peer-reviewed article and there is no abstract available. The author has lots of articles to his credit listed at pubmed, which you can get to from the CDC site, but I couldn't find any follow-up that discussed the specifics of this issue.

Hope you are all recovered from this experience - I haven't had Lyme (yet) but it's certainly something to worry about. Luckily for us, Claire has a great fact sheet about it, and she keeps it up to date!

Here is a link that might be useful: Horse and Deer Flies, at OSU

    Bookmark   March 5, 2007 at 8:14PM
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Thanks for passing along the info. If the fly is a vector it is probably a rare one, but it is still good to be aware of the (apparently very low) probability. It would hardly be the first time a fly has been a vector of an infectious disease!

It's interesting how that happens. So many of the flies concentrate on feeding on animals in one way or another. In like fashion many of the "Homopteran" insects (aphids, mealybugs, psyllids, adelgids, various kinds of scales) concentrate on sucking plant sap, and in like fashion are probably the primary insect vectors for plant diseases.

    Bookmark   March 5, 2007 at 9:19PM
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diggingthedirt I'm not coming down on you with this post; I just don't want someone to read your post and somehow dismiss deer flies as a vector. This is a very serious issue and I had a conversation similar to yours with my doctor. Once she understood that the deer fly was actually on me when I hit it, it was clear to her that the deer fly had done something. So to clarify, I have three theories about what happened: (1) The deer fly had already bitten me and I just didn't feel it. (2) It bit me right when I smacked it, so I didn't feel the bite because I could only feel the stinging sensation of having slapped myself at the same time. (3) The deer fly was about to bite me and by smacking it on my foot rather than shooing it away and then smacking it, I somehow shoved its mouthparts into my foot myself and just didn't realize it at the time. As a side note, since I am allergic to things that sting and have a bad reaction to other biting insects, I wouldn't have expected to develop the typical bullseye rash.

I may or may not have been bitten in the usual sense, but clearly something happened to my foot right where the deer fly had been. These photos were taken just a few days after the bite, 3 days after that, and then a little over a month after that. The photos don't show the shades of purple and black that were so hideous in real life, probably because of the camera flash. My doctor said the skin was necrotic. Obviously something happened, whether I was bitten, inadvertently self-injected, or what have you. I still have a weird dark blotch on my foot and this is almost 7 months after that last photo. It would have been a bizarre coincidence to have been bitten by a tick in that exact same spot any time just prior to the deer fly incident. And I can assure you that I was fixated on that spot ever since the moment I smacked it because it had a very numb, creepy-crawly sensation. Because of being fixated on it, I can safely say there was never a tick there from that point onward. That was the only "rash" on my whole body and I'll point out again that the first test showed I didn't have LD and then the next test showed that I did have LD, so the timing for a tick bite would have been oddly coincidental.

I guess people can draw there own conclusions about whether deer fly bites are something to worry about, but if my son were ever bitten by a deer fly around here, I wouldn't just dismiss it as a plain old deer fly bite.

    Bookmark   March 7, 2007 at 8:24AM
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Eight days ago I was bitten by a deer fly - I felt it and saw it! After two days, at the site of the bite the bullseye rash that is symptomitic of Lyme disease appeared. Although she has prescribed suitable antibiotics, my doctor was unwilling to diagnose Lyme however because I know it was a fly that bit me. I shall make sure she sees this. Thanks

    Bookmark   June 17, 2009 at 11:11AM
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spedigrees z4VT

All I can say is I'm glad that we and our dogs and pony all are innoculated against Lyme disease. Not that it will help against other tick and insect borne diseases. It's a jungle out there!

    Bookmark   June 17, 2009 at 11:34AM
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I thought I read that the vaccine for Lyme disease was declared ineffective and removed from the market. for humans anyhow. My dog still gets the vaccine.

There was something I read about how to prevent the mice from spreading it or whatever they do to contribute to it. Mice are part of the big picture.

    Bookmark   June 17, 2009 at 8:18PM
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cloud_9(z5 CT)

A friend recently told me that his doctor prescribes a single pill antibiotic as a prophylactic to LD when he gets bitten. Maybe, since transmission of the disease is unlikely before 48-72 hours, it wouldn't be appropriate for every tick for those of us who get multiple bites and are vigilant, but for those sneaky ones that are deeply embedded and may have been missed the night before, (especially the scalp ones) I think in this area it is a good idea.

Here is a link that might be useful: preventing Lyme Disease

    Bookmark   June 17, 2009 at 9:41PM
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spedigrees z4VT

The vaccine's manufacturer claimed that they pulled it for a lack of market/interest. However it is believed that there were adverse events that the drug co didn't want publicised, and I've read articles that seem to suggest if you have ever had Lyme disease and were still harbouring the virus, vaccination could pose a danger.

This is too bad considering the vaccine's high rate of efficacy in preventing the disease.

We got the full series before it was pulled, and it is highly unlikely we have ever had the disease, as it was still fairly rare here in northern NE at the time. As far as we know neither of us has ever been bitten by a tick, although I suspect that day is coming. :-(

The horse vaccine was never marketted but did well in the clinical studies. It is however nearly identical to the dog vaccine, and many horse owners (myself included) innoculate our horses every year along with our dogs.

I hope deer flies do not become a more likely carrier as time goes on, because we have many more of those nasty buggers than we do ticks. The tick population is expanding though.

    Bookmark   June 18, 2009 at 10:49AM
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claireplymouth z6b coastal MA

A local "Gentleman Farmer", or maybe "Gentleman Rancher", keeps fancy long-haired cattle, maybe Scottish Highland, but I'm not sure what type. Anyway, they also have a large flock of helmeted guinea fowl coexisting with the cattle.

Guinea fowl are notorious tick eaters, so I assume that's their main function - protecting the cattle from ticks. They're also fun to watch (and listen to). Not practical for the average gardener, but something to keep in mind.


    Bookmark   June 18, 2009 at 12:09PM
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pamcleod(z4 NH Lakes)

Thanks for this interesting information. I live on a farm, and deer flies are a huge problem with our horses and livestock. A few years ago, I ran across information online and wanted to share some of the ways which deer flies can be controlled. Many people don't realize that deer flies are VISUAL hunters and not attracted by scent as mosquitos are - they are drawn to moving objects and high contrasts (my black and white horse is tortured by them).

Because of this, it's actually fairly easy to build or buy deer fly traps, homemade or commercial. In the links below is a link to a researcher from Univ. of S. Florida who has some great recommendations. My husband has a blue flowerpot sticky trap mounted on his tractor in July & Aug, and we also hang them around the pasture and garden. Also, horse catalogs sell sticky patches which can be mounted to your back or the back of a ballcap - deer flies often circle around before biting and these sticky patches can attract them before they choose to land on your skin.

Here is a link that might be useful: My Deer Fly links on

    Bookmark   June 19, 2009 at 10:24AM
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claireplymouth z6b coastal MA

nandina, who is a New England ex-pat now living in Florida, sent me the link to the same research pamcleod cites.

This is the direct link re the Trolling Deer Fly Trap.

Some interesting and amusing user testimonials with trap variations.

I admit I thought at first it might be a joke, but apparently it really works.


    Bookmark   June 19, 2009 at 1:36PM
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The Trolling Deer Fly Trap really does work, Claire. Some thoughts about it plus some additional "also works" ideas about deer fly. You probably will have to order the Tanglefoot Insect Trap Coating on line. Reliable company with good customer service. Try painting the crown of a cheap, broad brimmed straw hat bright blue and then spray with the Trap Coating.

During deer fly season always have a hat with a hat band on or within reach. When they attack, break off pieces of shrub/tree branches (about 12"-14" long) or pull up tall fern fronds and stick them upright in the hat band. Great short term method that allows one to finish a round of golf or a stroll in the woods without being bitten. Try it.

    Bookmark   June 20, 2009 at 7:46AM
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pamcleod(z4 NH Lakes)

I was skeptical at first, too! I was visiting my folks in Wyoming last summer and showed these to my dad. The next day, he had a whole assembly of blue spraypaint, tanglefoot, and plastic pots lined up. They have 110 acres and it's wide open. He "trolled" on his tractor and came back with hundreds of deerflies in the tanglefoot.

    Bookmark   June 20, 2009 at 9:34AM
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claireplymouth z6b coastal MA

What do you when the pots/caps are covered with flies? Can you remove the flies and reapply the Tanglefoot, or apply new Tanglefoot over the bodies, or do you have to throw the trap out and start all over?

Claire (who is thinking about a whole new FAQ....)

    Bookmark   June 20, 2009 at 12:12PM
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pamcleod(z4 NH Lakes)

Good question, Claire! We haven't set them up yet for "year 2" here in NH, but I suspect we'll just spray Tanglefoot right over the top of last year's.

Here's another link - many online catalogs carry these patches, which you can simply apply to a hat.

Here is a link that might be useful: Deer Fly Patches

    Bookmark   June 20, 2009 at 6:25PM
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I was bitten by a deer fly last week. I forgot all about it. Two nights later I kept waking up with an aching ankle. The next day I saw an oblong, scarlet oval over the bite. I thought maybe a spider had bitten me. The bite site swelled. The ankle below it swelled. The site turned darker and darker until it turned purplish. Finally someone reminded me about about the deer fly bite. I was in SE Louisiana when this happened. I flew home to Michigan, where the bite just got hotter and more swollen. I called the doctor. They called me in and gave me anti-biotics to take because it's suspected that deer flies are carriers of the Lyme disease virus. Today the scarlet patch has turned dark around the edges and has less color in the middle. This is probably just an allergic reaction to the saliva, hoping so. I am relieved that the doctor is being cautious and treating it preventively.

    Bookmark   May 7, 2011 at 11:33PM
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I have never heard of Deer Fly as a Lyme disease vector, but when I have time I will check on it. I do know that it takes a Tick at least twelve hours of feeding to pass the virus to a human. But what is really important is the use as antibiotics without confirming that you have Lyme disease. The antibiotic that is effective against Lyme is toxic to the liver and should never be taken without due cause. Also any doctor that prescribes antibiotics without identifying the problem, (except in life or death situations) is a quack and should be avoided. This practice is contributing to the increased resistance problems and your doctor should know this!!!

    Bookmark   May 8, 2011 at 11:51AM
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The CDC still maintains that deer flies don't transmit Lyme Disease.

A google search still shows up that one letter, NE J Med 1990 Jun 14; 322(24):1752, but now it's quoted by agencies: e.g.

"Deer flies and horse flies are also suspected of transmitting Lyme disease (New England Journal of Medicine 322:1752, 1990). at a URI site about flies (at

If you google "horse flies" "Lyme disease", guess what will show up at the top? (here's a hint: you're looking at it).

Here is a link that might be useful: Lyme at CDC

    Bookmark   May 8, 2011 at 5:24PM
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Yes! I believe it is... I was bit by a deerfly (and I killed it and saw) I was also bit the same day by other deerflys around my ankles.. but the one I killed (and got me) turned to a bulls eye within 24 hours. Went to dr's took a photo.. Was put on antibiotics immediately Just got results (waited until Oct to get tested) and IGG positive but western negatives.. Just be careful I believe you can contract it through deerflys. The Michigan Ministry of Natural resources actually warn against it.. Happy gardening!

    Bookmark   November 24, 2011 at 8:48PM
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The reason that the Lyme bacteria are only transmitted by ticks after prolonged feeding times (my most recent source says 36 hrs) is that they needs to change their cell surface proteins in order to become infectious. They reside in the tick's stomach. When the tick begins to feed, and ingests warm blood, it triggers a change in the bacteria and causes them to manufacture new proteins and swap them for some of the existing ones on their surfaces. This is a process that takes some time, and when they're ready, they migrate to the tick's salivary glands, from which they can be injected into their new victim. Without this protein change, they're not infectious, which is why, for instance, you can't get Lyme disease by eating an infected tick. I know that deer and horse flies feed on deer, and probably ingest Lyme-containing blood, but I'm not sure if they can transmit it effectively, because they feed so very briefly (ticks stay attached for several days). Don't forget--it's not always the tick you see that gives you Lyme disease, and the bullseye rash doesn't always appear at the bite site--it can develop elsewhere. As for white-footed mice, they are the definitive hosts for Lyme disease, and are fed upon by first stage ticks (larvae). Deer ticks can transmit the disease in both the nymph and adult stages, but more effectively by the latter.

@IpmMan: The reason doctors use antibiotics prophylactically in cases of known or suspected tick exposure is because the Lyme bacteria can be eradicated from the body only in the first few weeks after exposure. After that, they hole up in the lymph nodes and become permanent residents and cause a variety of disease syndromes. In fact, the best time to treat Lyme disease is BEFORE the blood test is positive, in those early weeks. The disease is responsive to antibiotics at any stage, but can only be eradicated early on. Once it reaches the more chronic form, bacterial numbers can be decreased with treatment, but not wiped out. I hope this answers a few questions.

    Bookmark   July 6, 2012 at 2:55PM
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Thanks for that update.
@kathymilligan, WRT the Michigan DNR (department, not ministry), they actually don't claim that deerflies can transmit the disease, only that they can carry it - which is very different!

"The black-legged tick, Ixodes scapularis, is the most common carrier of Lyme disease in the mid-western and eastern states. I. pacificus is known to be the vector in the west. Other species of ticks such as the dog tick or wood tick, the lone-star tick and the rabbit tick, and biting insects such as mosquitoes, deer flies and horse flies have been shown to carry the Lyme disease bacterium. However, their ability to transmit the disease is not known at this time."

    Bookmark   July 7, 2012 at 9:15PM
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In order to avoid transmitted diseases and the nasty bites in the first place, you need to trap the deer flies. I have an incredibly effective method (I've trapped over 11,000 deer flies in just the first 5 weeks of the 2012 deer fly season in Michigan) using an umbrella, blue cups, and Tangle-Foot. Details and data can be found at my blog

Happy trapping and good health to you!

Here is a link that might be useful: deer fly trap umbrella

    Bookmark   July 10, 2012 at 2:01PM
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