Saturday, May 26, 2012

More Creepy Crawlies

by Jennifer Coates, DVM

In my last post I talked about venomous snake bites. Today, something a little less scary (for most folks, at least)… spider bites.

I should start out by saying that after the great majority of spider bites, owners won’t have the slightest idea that anything is amiss. 

Your dog might be a little itchy around the bite site, but rather quickly that subsides and life returns to normal. What I’m going to talk about are those thankfully relatively rare occasions in North America when spider bites present a serious risk to health.

Black Widow Spider. Image: National Geographic
The Black Widow

When I practiced in southern Virginia, I saw a few dogs that I suspected had been bitten by black widow spiders. They exhibited the typical symptoms of this spider’s venom, which is a neurotoxin.

The dogs all had muscle rigidity, tremors, and were in pain. I treated them symptomatically (e.g., fluids, pain relievers, muscle relaxers, and the like) and they all recovered. This is the most common scenario when the individual that is bitten is fairly large. When petite dogs, cats, or other small animals are bitten by a black widow, the muscles necessary for breathing are more likely to be affected, which can lead to death. In these cases, a human black widow antivenin is available, but it may be prohibitively expensive for some veterinary patients.

Black widows reside primarily in warm areas with mild winters, but they have been found as far north as Canada.

Brown Recluse Spider. Image: The Inquisitr

The Brown Recluse

The brown recluse spider lives in the midwestern and south central regions of the United States. Its bite contains a toxin that destroys tissue, leading to pain and sometimes large wounds that develop days after the bite occurred. Treatment depends on the severity of damage but may include antibiotics, pain relievers, and surgery to remove devitalized tissues and deal with open wounds. Affected dogs may also require symptomatic treatment for nausea and a fever.

Secondary Infections and “Hot Spots”

Any injury to the skin, including bites from benign species of spiders, can become infected and/or irritated, particularly if a dog licks, chews, or scratches at the area. Relatively mild itchiness may respond to an oral antihistamine and/or topical anti-inflammatories. More severe symptoms respond best to a short course of a corticosteroid. An antibiotic ointment or spray may be all that is necessary to resolve a superficial skin infection, but oral antibiotics are often required in more advanced cases (particularly if your dog tends to lick topical preparations off before they can be effective!). If an abscess develops, surgery to drain it and deal with devitalized tissue may also be necessary.

If you suspect that your dog has been bitten by a spider, keep an eye on him. 

Just as is the case for people, most canine spider bites don’t require medical attention. But if your dog acts sick or develops a lesion at the bite site, it’s time to call your veterinarian.


Jennifer Coates, DVM graduated with honors from the Virginia-Maryland Regional College of Veterinary Medicine in 1999.  In the years since, she has practiced veterinary medicine in Virginia, Wyoming, and Colorado.  She is the author of several books about veterinary medicine and animal care, including the Dictionary of Veterinary Terms: Vet-speak Deciphered for the Non-veterinarian

Dr. Coates has recently joined the PetMD team and she is now writing for the Fully Vetted column; great blog, do check it out.

Jennifer also writes short stories that focus on the strength and importance of the human-animal bond and freelance articles relating to a variety of animal care and veterinary topics.  Dr. Coates lives in Fort Collins, Colorado with her husband, daughter, and pets.

Articles by Dr. Coates:
Kidney Disease – Say What? 
What Happens In The Dog's Body When The Kidneys Fail To Function Properly? 
The Perplexities of Pancreatitis
The Other Side Of The Coin: The Cost Of Defensive Medicine
To Neuter Or Not To Neuter… That Is The Question
Don’t Forget the Physical Therapy
Common Misdiagnoses (Part 1)
Common Misdiagnoses (Part 2)
Picking the Right Dog to Breed
When Is It An Emergency?
Dog Allergies: Common, Commonly Misdiagnosed, or Both? 
Why Does The Spleen Get No Respect?
Protect Your Dog From Snake Bites 

Related articles:
Spider Bites Dog 


  1. We have both venomous snakes and spiders here. Different ones though. I guess the worst ones might be the redback and funnelweb spiders. We used to have funnelwebs in our old house. Fortunately, neither Jordan nor Rufus ever got bitten because they can be fatal even for humans.

    Thanks for this info!

    1. Ouchie, funnelweb spiders in the house! So glad the guys never got bitten. To be honest, I'd rather deal with 10 snakes than 1 spider. Really hate those.

      Having to deal with neither is best. Kind of advantage of our climate, not so many creepy crawlies up here.

      Keep safe!

  2. Great, informative post - but those spiders looked scary!! I try to be a brave Dog, but I'm not brave when it comes to Spiders :)

    Hope you're having a fun day :)

    Your pal Snoopy :)

    1. Hi Snoopy, they don't just look scary, they are. So it's better not to be brave and run when you see one. (((hugs)))