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Can Black Widow Bites Kill a Dog?

can a dog die from black widow bites

Dog owners may wonder whether black widow bites kill a dog, considering the bad reputation of this type of spider. Spider bites are after all, often a dog owner’s worst fear. Spiders themselves are ugly, scary, tiny creatures, and their bite marks are easy to miss. Can black widow bites kill a dog? Black widows are not only unsightly to look at, but their spider bites are considered dangerous, if not even potentially fatal to certain dogs if treatment is not sought within a timely manner.


Picture of a black widow.

How to Identify Black Widows 

Most spiders do not pose a threat to dogs. The most common species that are dangerous to dogs are black widows, brown widows, and recluse spiders. There are other types of spiders, such as the wolf spider, that can produce a nasty wound, but aren’t fatal on their own.

Black widows are small, black and shiny spiders belonging to the genus Latrodectus. They range from half an inch to an inch and a half in length. Only female spiders have a blood red hourglass on their abdomen. Males lack this distinctive feature, and are much smaller, brown in color, and much less commonly known for envenoming.

Black widows are reclusive spiders and mostly found in dark, cluttered areas, usually rife with other bugs. Places like sheds, wood piles, bushes, drainage pipes, basements, or crawl spaces are their favorite hiding spots. If you have ever seen a black widow in your general area, then you can bet this is a location that they inhabit.

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Black widows are found in most continents including North America, South America, South Africa, Australia, Southern Europe, and Asia .

Appearance of Black Widow Bites on Dogs

Dog has thickened leathery skin

Can Black Widow Bites Kill a Dog?

If you spot a red, swollen area, it may be a spider bite. Some other symptoms of black widow spider bites in dogs may include itching, rash, pain, labored panting, anxiety, restlessness, and other malaise symptoms.

Something to consider is that a dangerous spider does not necessarily inject venom every single bite. It is estimated that 15 percent of black widow bites are "dry" with no venom injected. A bite without venom is called a “dry bite”.

Because a black widow's fangs are very small and dogs are equipped with hairy coats, and because the bites do not produce any significant local tissue reaction, a puncture may not be readily visible. Unless the bite is actually witnessed, trying to figure out what the bite was isn’t usually apparent immediately, but instead is deduced by a veterinarian from the onset and progression of symptoms. What you can do, however, is to figure out if black widows are around your home or live in your general location and climate.

If in doubt, call your local veterinarian to speak to someone about the bite, what the bite looks like, how your dog is acting, and your dog’s specific pre-existing health issues. If your local vet isn’t open, call the emergency vet. They will know what types of spiders are local to the area, if there has been an influx of spider bites lately, and how your dog’s symptoms and wound site compare to the different types of spiders. Consultation over the phone is free and does not cost you anything, so save yourself some time and peace of mind.

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Can Black Widow Bites Kill a Dog?

If your dog got bitten by a black widow, there isn't much that can be done at home. First aid is essentially of no value when it comes to black widow envenomation.

Clinical symptoms of black widow bites in dogs generally appear within eight hours and mainly affect the nervous system. The venom induces the massive release of the neurotransmitters acetylcholine, norepinephrine, dopamine, glutamate and enkephalins.

Symptoms include loss of sensation, sensitivity at the bite site, muscle spasms, restlessness, incoordination and trouble breathing. The hallmark sign is a tense abdomen without tenderness. Pain, high blood pressure and a high heart rate may arise and seizures and paralysis may set in in severe cases which can turn fatal.

Can black widow bites kill a dog? Generally, small dogs and cats can sometimes be potentially killed by the bite of a black widow, but large dogs fare much better. At risk are for the most part, smaller animals that are very young or very old, explains veterinarian Dr. Bruce. In cats, single bites are potentially fatal.

If your dog wasn't bitten, but actually ate a black widow read this: Help, my dog ate a black widow spider.

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At the Vet's Office

Once you get to the vet, the first thing that will happen is that the vet will assess the wound, your dog’s health, the medical history of the dog, and discuss with you what type of spider that it may have been. If needed, they will put your dog into assistive care, such as an IV or oxygen breathing assistance.

Next, may come anti-venom treatments to counteract the spider’s poison. Black Widow antivenin, known as Lyovac [Latrodectus] antivenin may be given if available. This antivenin isn't very costly and it's quickly effective often causing resolution of symptoms within 30 minutes.

If no antivenin is available, your vet will likely provide supportive care through painkillers, or possibly muscle relaxants (10% calcium gluconate) to treat the muscle spasms caused by the venom in the bite. The vet may also prescribe anti-seizure medicine if the situation warrants it.

Most spider bites won’t keep your pet at the vet overnight, and treatment will continue at home. Administer the medications prescribed by your vet and call the office if you have any questions, if anything gets worse, or if there are any changes.

If your dog shows any symptoms like muscle weakness, paralysis, partial paralysis, disorientation, or extreme difficulty in breathing, it is time to go to the emergency vet as soon as possible. These signs are potential symptoms of a widow spider bite and they need professional medical treatment immediately, as widow spider bites progress quickly.

Please note! If your dog is experiencing these symptoms, call the emergency vet ahead of time. If they don’t have the proper anti-venom to help your dog, it will be time wasted in transit. They may also be able to prep a room and treatment for your arrival. Or, if they are overwhelmed with other pet emergencies, they can direct you to another treatment center. If you have someone else with you, they can give your passenger special care directions to help assist your dog in transit.

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