Featured Poison

Fire Ants: The Sting that Burns

I don’t write a lot about insects, but there’s a good reason for it. I’m allergic to insects. Pretty much all of them. If I get bit or stung I swell up and ooze pus for a week. I was that kid that almost died from a mosquito bite on his neck when he was five. Thanks, Dr. Bor*, for that shot of epinephrine in the hospital parking lot. So venomous insects give me a touch of anxiety, even when writing about them, but I’ve got to get over it.

* He was my pediatrician. I’m not sure he liked kids though, either that or it was just me. He wasn’t tolerant of my crap and yelled at me. “Stop crying like a baby,” he’d say with his heavy Czech accent. When I was in 5th grade I broke my pinky. I don’t know how, I just looked at it during recess and it was at a 90-degree angle from the rest of my digits. My mom picked me up at school and we drove over to see Dr. Bor who took one look at my finger and proclaimed “It’s just dislocated.” When I tried to protest he grabbed my finger and gave it a tug to “pop it back in place.” I can still hear the Rice Krispies crunch of bone shards rearranging themselves in my mangled finger. It wasn’t pretty and it hurt like hell. “Stop crying,” he said, as he ushered us out to go see an orthopedic doctor. Despite all this Dr. Bor was a good doctor and I was lucky to have him. He was a Holocaust survivor and at a young age hid from the Nazis for nine years while his entire family was murdered. Sadly, Dr. Bor is no longer with us, but please read more about his remarkable life in his obituary: Dr. Imrich Bor, Survivor Of Holocaust, Pediatrician.

Living in the southern United States, “The South,” isn’t a place anyone allergic to insects should live. Bugs, like the sharpshooting walkingstick, are everywhere. In the summertime, if I step outside, even for a moment, I come back with a half-dozen mosquito bites. But the worst? Fire ants.

Fire Ant Hill by Vicki DeLoach (CC BY-NC-ND-2.0)

Fire Ant Hill in north Georgia by Vicki DeLoach (CC BY-NC-ND-2.0)

There are a few hundred species of ants in the Solenopsis genus but only a select few have earned the name “fire ant.” In the American southeast, the dominant species is the invasive red imported fire ant, Solenopsis invicta, coming by way of South America. They were introduced into the United States – accidentally I hope – by way of Mobile, Alabama in 1940 and quickly spread throughout the southern states. They truly are a plague. Besides displacing native ant species, fire ants create massive environmental and economic losses due to predation upon small animals, like songbirds, and livestock such as chickens and calves. The economic cost to just the state of California due to the red imported fire ant is estimated to be nearly one billion dollars. One billion! Infestations are easy to spot though, as they make large mounds from soil and sand to house their colony, some reaching 2 feet in diameter. Even though it may seem like mounds pop up overnight, fire ants work steadily for months creating their colony. Large colonies are made up of 250,000 ants, supplied by a Queen that can produce up to 1,500 eggs per day. This is terrifying, but the worst is yet to come.

Fire Ant by Rick Hagerty (CC BY 2.0)

Fire Ant by Rick Hagerty (CC BY 2.0)

Fire ants bite and sting. They dig into your skin with their powerful mandibles to get a good grip before they inject venom from a stinger located on their abdomen. Did I mention they can sting you multiple times, over and over again? Well, they do. Their stinger is a modified egg-laying organ called an ovipositor, so only female worker ants are capable of envenomation. I don’t think male fire ants do much of anything. Reactions to fire ant stings can vary, depending upon the individual’s sensitivity. Most people feel the initial sting, which swells into a little bump within a few minutes, then the pain begins. It starts with a warm sensation that gradually progresses to an intense burning – hence the name “fire” ant. The next day those little bumps develop into fluid-filled pustules that resemble a pimple. They’ll eventually dry up and go away. For me though, the pustules grow about an inch in diameter and constantly ooze pus for several days. I usually get stung on the ankle and my socks get soaked with nasty yellow ooze. In a week the pain will be gone and I’ll be left with a scar that fades over the years. If I get enough bites – like 4 or more – I feel physically ill: weak, feverish, flushed, just a general malaise. It sucks for me, but at least I’m alive. For some, fire ants can be deadly.

On a warm Texas day, a 30-year-old woman drove onto a field to change the oil in her car. She crawled underneath her car to remove the oil plug, but before she could do so she scrambled to her feet. She had a dozen or so fire ants on her back and shoulders, which her male companion brushed off, but within minutes she was short of breath. EMS was called and on arrival, she collapsed. Epinephrine was administered and she was rushed to the ED, but never regained consciousness. She was pronounced dead less than an hour after contact with the fire ants. She clearly had an adverse, anaphylactic reaction to fire ant envenomation which was supported by her laboratory work and a history of being “allergic to fire ants” supplied by her family. (1)SolenopsinWhen fire ant venom is injected, the body generates an immune response and antibodies immunoglobulin E and G are recruited to the site of the attack. When an allergen in the venom binds to these antibodies, mast cells – a type of white blood cell – burst open, releasing histamine and other chemicals, giving rise to the typical swelling, redness, and itch. That’s why we take antihistamines for these sorts of things. Most venoms are a concoction of various components: proteins, anticoagulants, lipids, and sugars, to name a few. Fire ant venom is a bit unique in that 95% is made up of a mixture of alkenylpiperidine alkaloids known collectively as solenopsins (2). One of these, solenopsin, has several interesting biological activities that explain why a fire ant sting is so much worse than a mosquito’s. Solenopsin inhibits angiogenesis and neuronal nitric oxide synthase (nNOS). Angiogenesis is the process of making new blood vessels and is important in wound healing. Nitric oxide synthases are enzymes that catalyze the production of nitric oxide, which aid in tissue regeneration and the wound healing process (3). This is partly why my wounds don’t heal quickly: new blood vessels and tissue formation necessary for wound healing are slowed. It’s the aftermath of the sting that is so agonizing, not the actual sting itself.

We’ve established that fire ants are a nuisance to the environment and my ankles, so how to get rid of them? Some people use commercial insecticides, others use homebrewed concoctions of baking soda and vinegar (to kill them with carbon dioxide?). A very southern method and one that I don’t recommend is to kill them with fire. I’ve seen way too many deaths from people tossing gasoline on fires. If you don’t die a horrible death you run the risk of burning your house down, like this English gentleman: Man sets his house on fire trying to kill ants. So stay away from the fire ant mounds…and the gasoline.

References:

  1. Prahlow, Joseph A., and Jeffrey J. Barnard. “Fatal Anaphylaxis Due to Fire Ant Stings.” The American Journal of Forensic Medicine and Pathology 19.2 (1998): 137-42.
  2. Chen, Li, and Henry Y. Fadamiro. “Re-investigation of Venom Chemistry of Solenopsis Fire Ants. II. Identification of Novel Alkaloids in S. Invicta.” Toxicon 53.5 (2009): 479-86.
  3. Frank, Stefan, Heiko Kämpfer, Christian Wetzler, and Josef Pfeilschifter. “Nitric Oxide Drives Skin Repair: Novel Functions of an Established Mediator.” Kidney International 61.3 (2002): 882-88.

** Homepage featured image of Fire Ant by Rick Hagerty (CC BY 2.0) **

4 thoughts on “Fire Ants: The Sting that Burns

  1. How about boiling water? I have seen these guys make incredible rafts of their bodies after flooding from a hurricane. You can Google for photos…pretty neat.

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