could deadly black widow spiders be lurking in your house?

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Posted by Dr. Kim Smyth on Oct 20 2014


As a veterinarian, I love animals. I love all living creatures, actually, even down to the tiniest ant (except fleas and ticks—I really hate those!). Every so often, I find myself in an insect moral showdown. Last summer, it was with the wasp nests on my porch—on one hand, I feel terribly guilty killing them and ruining all of their hard work (after all, it takes ages to build those nests!), and on the other hand, I know that they could cause harm to me or my children (both two and four-legged). Should I kill the wasps just for the potential harm they may cause us?

Well, last year, the wasps won, much to the shock and dismay of neighbors who thought I was crazy. And I probably am. But the wasps led a good life on my front porch and never bothered us once.

Yesterday, though, the insect world decided to up the ante. I was in the garage doing a bit of organizing, and I dropped a book, sending it tumbling through a spider’s web which in turn sent its maker scurrying to find shelter. It was a big, shiny black spider, and as she turned to curl up in the corner of the shelf I saw it: a bright red hourglass on her belly.

Black widow spiders are notorious for a reason—they are dangerous to us and potentially deadly to our pets. This lady’s web was full of remnants from old meals, so who knows how long she’s been living in that bookshelf. If you thought my moral dilemma about the wasps was crazy, you’re going to think I’m even crazier now when I admit that I also felt it for the black widow spider.

Black widow spiders are found in every state except for Alaska, but they’re more common some places than others. On the east coast, they’re found in Maryland and points south. The northeast has their own troubles with ticks that carry Lyme disease, so they’re mostly off the hook with black widows.

When you see the infamous large black spider with an hourglass on its underbelly, you know you’re looking at an adult female black widow spider. Immature females are brown in color and lack the characteristic hourglass, but they are still capable of causing severe envenomation, so watch out for them, too.

Black widow spiders aren’t aggressive—they won’t hunt your or your pets down. But they will defend their web and their life if they are provoked.

Unlike snake bites and bites from other venomous spiders, like the brown recluse, black widow bites cause systemic signs rather than local inflammation of the skin and muscles surrounding the bite site. Signs in dogs include:

  • muscle stiffness or cramping, especially along the back
  • abdominal stiffness/cramping
  • respiratory distress
  • extreme generalized pain

Cats are particularly prone to the effects of black widow spider venom, and bites can easily cause death. Salivation, restlessness, vomiting and severe pain occur after a black widow bite. Muscle cramping and incoordination progress to complete paralysis and death.

It is difficult to diagnose a pet with a spider bite—often the bite sites cannot be found under thick fur, and rare is the pet owner who watches their dog or cat every second of every day. Bee stings, snake bites and spider bites can all happen in an instant, even if we are careful about where our pets frolic and play.

Treatment of black widow spider bites consists mostly of treating specific symptoms. Prescription medications are used to control tremors, lower high blood pressure and treat pain. There is a black widow antivenin which has shown great success in humans, though it might not be practical for your local veterinary clinic to carry it considering its cost.

Black widow spiders are dangerous, and it’s fair to say that if your pet has been bitten, she’ll need to be hospitalized for several days to give her the best chance at recovery. Even with aggressive treatment, cats often succumb to black widow spider bites.

So, after considering all of these things, I decided that the black widow had to go. I came inside to ask my husband if he thought simply relocating her to a home outside the garage would be sufficient (he is a sane, rational human being, so of course he said NO!), but when I went back to the garage, she was gone. I will still look for her daily, and when I see her again, I won’t hesitate (well, maybe just a little), because if it’s her life or my cat’s life, it’s an easy choice to make.