HOW DO WE KNOW WHAT HAS BITTEN OR STUNG US?

by Whit Gibbons

July 20, 2008

The following query, which I received last week, is longer than most queries I get, but it articulates a common conundrum.

Q. My wife is a service technician whose work involves crawling under houses, connecting wires inside unsealed enclosures, wading through underbrush to access phone line pedestals, and other activities that almost daily expose her to encounters with bees, spiders, and snakes. While doing outdoor wiring last week, she took the normal safety procedures of banging on the box to make sure no wasp nest was inside and slowly opening it with a long screwdriver in case there was a snake. No critters were detected, so she began her work. As she reached in to disconnect some lines around the connector block, she felt a severe burning sensation, much stronger than a wasp sting, on the inside of her thumb.

That evening her hand was swollen and what looked like a small water blister was at the point where she was bit/stung. I could see no sign of a stinger or body part, but saw three tiny spots that could have been punctures. The next morning the bite area was extremely red, her entire forearm was reddish almost to the elbow, and her hand was miserably uncomfortable. Her doctor said it was a black widow bite and gave her antibiotics and steroids. Could any other spiders or insects produce such a reaction? A friend, also a medical doctor, told us it was more likely a brown recluse. We know that spider and snake bites are uncommon but people like to attribute their wounds and pain to something exciting and interesting rather than the most likely culprits--ants, bees, or even thorns. From your experience, does this sound like a black widow bite?

A. Confirming what bit or stung your wife is probably not possible at this point, as a variety of creatures can cause such symptoms and people's responses to venom are extremely variable. Highly toxic species can deliver venom in quantities so small that no reaction is evident. Or they can inject higher levels that cause severe problems. Further variation in responses is due to the physiology of the person. For example, a bee sting can be an unpleasant but short-term event for one person whereas someone else may experience a systemic reaction that can be fatal. Factors of age, medical history, body weight, and even whether someone is taking antihistamines at the time can make a difference in how a person reacts to a bite or sting.

Thousands of invertebrates (including virtually all spiders) are capable of injecting venom, although some animals are too small to affect us. Anther option for what bit your wife is a centipede, which could very well be in the type areas where she puts her hands. I have been bitten twice by centipedes, and the symptoms you describe are similar to my own experience, especially the red dots and reddening of the arm. A wolf spider or other large spider is also an option or, in some parts of the Southeast, a scorpion.
People can vary considerably in their responses to a brown recluse or to a black widow bite. And many of the reports about how these spiders affect us are probably flawed because in speculating about what caused the bite or sting the attending physician or nurse indicted the wrong species (which may have been neither one of them) with the ensuing symptoms. All told, our reactions to the bites and stings of venomous animals are so variable that sometimes neither biologists nor medical doctors will be able to diagnose the cause when the animal itself is not seen.

As you say, it might be "exciting and interesting" to hear an expert declare that "the animal that bit (stung) you is the rare and potentially dangerous three-eyed rock monster," but sometimes the experts are just guessing. Very few, in fact let me change that to "none," have observed all of the physiological responses that can be expressed by humans to the myriad invertebrates that defend themselves against us.



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