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Help, My Dog Ate a Black Widow Spider

Help, My Dog Ate a Black Widow Spider

If your dog ate a black widow spider, you are rightfully concerned; black widow spiders have a neurotoxic venom which can cause significant problems to dogs. However, what makes a difference on the outcome of the situation is primarily whether your dog just ate the black widow spider, or if he also got bitten in the process. Often determining whether your dog got bit or not can be tricky, but most dogs will manifest signs of pain. When in doubt, it is always best to play it safe and consult with a veterinarian. Left untreated, black widow bites can be fatal in some cases.

black widow dog

About Black Widows

Black widows (latrodectus spp.) are spiders that are common in many parts of the world. They tend to measure around three quarters of an inch in diameter. In most cases, the females are easily recognizable by their shiny black color and red or orange signture hour-glass marking found on the bottom of their abdomen. Male spiders instead tend to be brown and lack the typical red hourglass marking.

The bite of black widow spiders are venomous due to the the presence of latrotoxin, a neurotoxin which evokes the release of neurotransmitters. Bites from females are concerning due to the fact that have larger venom glands. Males are not a threat and are considered harmless.

Not all bites are harmful though; sometimes black widows may not inject any venom, resulting in what is called a "dry bite." It is estimated that 15 percent of black widow bites are dry.

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Black widows are not considered to be aggressive spiders. They're pretty much shy creatures that are not looking for trouble. Bites most likely occur when they are trapped or bothered/provoked by person or animals such as an inquisitive dog.

Did you know? A black widow's web is known for being particularly strong. Their webs are typically found near ground level by building foundations or in small holes and don't appear to be organized as typical spider webs are, but they're rather uneven and tangled. Black widow webs are composed by three structural layers: an uppermost portion, a central portion and a lower portion.


If Your Dog Ingested the Spider

dog ingested Neosporin

If your dog just ate the spider and there are no signs of being bitten, then there is good news for you. While a black widow spider's venom is concerning when it is injected into the dog's skin, the venom is likely to become inactive once it reaches the dog's stomach courtesy of the dog's stomach acid, explains veterinarian Dr. Drew. At the most, the dog could develop digestive upset.

The not so good news though is that black widow bites can be tricky to detect. The bite puncture wounds are very small and there may be no significant local reaction. On top of that, dogs are equipped with heavy coats, which makes diagnosing a black widow bite difficult, according to DVM360 staff.

The bite is therefore suspected based on the dog's history (being around a black widow) and clinical signs, but to make matters worse, consider that there are many other conditions that can cause similar symptoms and there is no blood test that can reveal presence of black widow venom in the dog's bloodstream.

If you suspect your dog was bitten by a black widow spider, it's therefore important to play it safe and see your vet. The earlier a potential bite is detected, the better.

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"Eating a dead poisonous spider will cause no more problems than eating a dead non-poisonous spider. The spider's toxin is only dangerous when injected into the body. The toxin will be denatured in the stomach and pose no risk."~Dr. Pete, veterinarian

dog teeth

If Your Dog Got Bitten

If you suspect that your dog happened to be bitten by a black widow spider, consult with your vet. If the spider was alive when your dog ate it, there are chances it may have bitten the dog on the inside of the mouth before being swallowed.

The level of toxicity of black widow bites ranges from generally moderate to severe and life threatening. Generally, small dogs are more at risk than large dogs and young puppies and older dogs are more at risk for complications. Dog with certain underlying medical problems (high blood pressure, weakness) may be more at risk.

Symptoms may have a brief delay and generally show anywhere between half hour to two hours after the bite has occurred. The symptoms reflect the venom's ability to cause the release of norepinephrine, acetylcholine and other neurotransmitters followed by their consequent depletion.

Signs to watch for include: severe muscle pain starting at the bite location and then spreading to affect all large muscle groups (legs, back, abdomen, thorax), drunk-like gait, tremors, paralysis, drooling, nausea, vomiting, abdominal rigidity (one of the most characteristic signs), restlessness, changes in blood pressure, high heart rate and even death. Death occurs as a result of paralysis of nerves and muscles associated with breathing.

" The clinical signs seen in dogs include regional numbness, abdominal rigidity without tenderness, and muscular fasiculations. There is generally pain around the bite but it is seldom fatal to dogs."~Dr. Murl Bailey, Jr, veterinary toxicologist.

At the Vet's Office 

Causes of dog hallucinations

Upon reaching the vet's office, your vet will examine your dog, take blood work and look for any signs of trouble suggesting a black widow spider bite. If your dog was actually bitten, then treatment is mostly supportive.

Your vet may administer IV fluids, muscle relaxants (diazepam, methacarbamol), medications to treat seizures if present, and strong pain medications (opiods). While calcium glutonate was once used for treatment of black widow bites in the past, its use is no longer recommended and has now been replaced by more effective pain meds and muscle relaxants (Clark et al. 1992)

While there is antivenom for black widow bites (Lyovac antivenin) which works rapidly, ( in most cases within 15 to 30 minutes) the main drawback is that it isn't easy to find. Vets may need to track some down from human hospitals and the costs may be quite high or almost prohibitive in some cases.

Recovery from a black widow spider bite may take time and it is not unusual for the weakness and paralysis to persist for several days or, in some complicated cases, weeks or even months.


  • Veterinary Toxicology: Basic and Clinical Principles, edited by Ramesh C. Gupta, Ramesh Chandra Gupta
  • Nordt SP, Clark RF, Lee A, Berk K, Lee Cantrell F. Examination of adverse events following black widow antivenom use in california. Clin Toxicol. 2012;50(1):70–3
  • DVM360: Venomous varmints and other creepy-crawly creatures (Proceedings)

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