Spider Bites on Dogs – How To Know When A Spider Bites Your Dog

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Spider Bites on Dogs…Awareness, Detection and Protection

In this article, we’d like to give you some quick but sage advice about spider bites on dogs…with your  particular dog being the one in mind here.  It is important to note, right out of the gate, that spider bites on dogs are a bit of a tricky business.  

The reason being, is that it is super difficult to confirm for sure that your dog has actually been bitten by a poisonous spider unless you actually see the spider on the dog with spider bites on or around that same spot.  

With that said, we’ll address such questions as which spiders to be on the alert for, how these spiders might or might not affect your precious pup, and what to do about it.  First, let’s identify two spiders that actually have the ability to send your hound to the vet.

Which spiders should my dog be worried about?

There’s good news and bad news with regards to poisonous spiders potentially biting your dog.  There are indeed a large number of venomous spiders in the United States that can potentially harm your dog.  

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That’s the bad news.

However, the good news is that dogs have thick, tough, skin that most spiders can’t penetrate with their bite even if they try.  That’s the good news.  Here’s the caveat…there are two particular poisonous spiders that roam these parts that both you and your dog should be on the lookout for.  Here they are in no particular order:

The Black Widow

Black Widow Bite On Dogs

Though they pose a serious threat, black widow spider bites on dogs are seldom fatal unless bitten several times.  Black widow spiders can be found just about anywhere throughout North America, according to the Centers for Disease Control and Prevention.  

Though there are three different species roaming North America (western, northern and southern widow) they all generally have the same markings, especially the female, which is the one that you want to avoid.  The female is distinguished by its shiny black body and red hourglass marking on the underside of its body.  

They sometime have a splash of red on their “backs” as well.  Widow spiders like dark, non-disturbed places. They can be found inside buildings or outside in leaf litter. Though very poisonous, black widow spiders are not aggressive and will only bite defensively.

Will my Dog Die from a Black Widow Spider Bite? 

Most likely not.  In fact, there’s even a small chance that your dog won’t be envenomed at all if bitten by a black widow.  According to the National Center for Biotechnology Information (NCBI), black widow spiders can control the amount of venom they inject and are even known to “dry bite” which means they don’t inject any venom at all.  

In fact, the NCBI reports an estimated 15% of bites to humans as being dry bites.  With that said, the reaction your dog might have to a widow bite varies greatly depending on the circumstances.  

Factors such as, where on the body your dog was bit, the amount of venom injected, and your dog’s size and sensitivity to black widow venom all come into play here. Even the season can affect how your dog responds to a widow bite, as higher temperatures seem to increase the toxicity of spider venom.

Signs and Symptoms of Black Widow Spider Bites on Dogs:

According to the NCBI, onset of clinical signs usually occurs during the first 8 hours of being bitten.  Widow spider venom is absorbed into the circulatory system where it causes neurologic signs.  

A hallmark sign that your dog has been bitten by a black widow is that their belly gets really tight and rigid without it being tender.

The bites are immediately painful.

 Black widows typically leave obvious bite marks on humans, with two small puncture wounds 1-2 mm apart.  However, this isn’t the case on our hairy K-9 friends and finding the actual bite marks are much more difficult.  In 30 minutes to two hours, muscle cramps will begin near the bite site and then spread to other large muscle groups.  Pain peaks in two to three hours.  High blood pressure and high heart rate are also common.  

As the signs progress, vomiting, diarrhea, paralysis and even death can occur.  The bite may initially go unnoticed by your dog, or it could cause a sharp, burning pain.  However the bite may manifest itself, here is a list of common symptoms of black widow spider bites on dogs:

  • Restlessness
  • Vomiting (It’s not unusual for the dog to vomit up the actual spider)
  • Diarrhea
  • Muscle rigidity, particularly the abdominal muscles
  • Seizures
  • Increased heart rate
  • Labored breathing, usually rapid and shallow
  • Weakness of the limbs
  • Paralysis

Treatment for Black Widow Spider Bites on Dogs

 If you suspect that your dog has been bitten by a black widow spider, contact your veterinarian immediately.  They may recommend administering Benadryl or an ice pack at home to prevent inflammation.  

They will likely not be able to determine the severity of the bite without actually seeing your pet.  Treatment often includes muscle relaxants and pain medications.  There is an antivenin, but it is typically hard to find (even for vets) and therefore rather expensive.  The good news is that even without the antivenin most animals (including dogs)

 The Brown Recluse

Let’s now shift our focus to the other nasty spider…the brown recluse.  These guys live mainly in the Midwest and South of the United States.

 They prefer to weave their webs in secluded, dry, sheltered areas such as underneath logs, or in piles of rocks or leaves. Indoors, they will build their web in a dark closet, in a shoe or in the attic.  According to the CDC, unlike the black widow, the recluse requires pressure against its body to bite.  This obviously would occur if your dog happened to lie down on one.

Signs and Symptoms of a Brown Recluse Spider Bites on Dogs

A brown recluse bite is much more skin related.  Very commonly dogs will develop blistering, redness and swelling that will ultimately turn black as the skin dies.  

This can progress over the course of days.  Whereas black widow venom tends to damage the nervous system, brown recluse venom causes cellular damage.  This obviously translates into black spots of festering dead or dying skin.  Sometimes you’ll find a lump under the skin before it gets to that point, but more typically it’s the redness and blackness that are the telltale signs.

Treatment for Brown Recluse Spider Bites on Dogs

Without the supportive care that a veterinary clinic can provide, an affected dog will eventually have rising blood pressure and heart rate, just like a dog bitten by a black widow.  

As with black widow antivenin, brown recluse antivenin is pretty ridiculously hard to come by so most vets will subscribe to a treatment of pain medication.  They’ll then provide supportive care for symptomatic treatment of any other skin complications that may develop.  Antibiotics might be administered depending on the degree of the skin problem.

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