Pets and Spider Bites

I am often asked if a spider can harm animals and the answer is most certainly “Yes”. I thought it would be handy to have some details on the effects of the most dangerous spiders on animals like cats and dogs for reference.  It’s very easy to tell if a  person has been bitten by a spider but it is quite difficult to do so in pets especially if they are furry (such as cats and dogs). Animals are more prone to infections if spiders bite them. That is why it is crucial that you know how to determine if your pet has a spider bite. A number of venomous spiders exist in the United States that can harm animal, though very few species of spider are equipped with the fangs and strength to penetrate a dog’s thick skin. The black widow, the brown widow and the brown recluse spiders, however, all possess that ability. If you have dogs, it would be wise to find out if these spiders are indigenous to your area and, if they are, to become adept at identifying them. The difference between a sign and a symptom is one is objective and one is subjective.

Signs & Symptoms:

A sign is something an observer can see, whereas a symptom is felt by the victim. Signs of a spider bite on an animal include swelling at the site of the bite. The eyelids, earflaps, nose and lips are vulnerable places on a dog because they are not covered by a thick coat of fur and their tissue is thinner than on other parts of the body. You may notice the animal having difficulty breathing if the bite is on his nose.

If the bite occurred in an area that is not covered by fur, you’ll see redness, swelling and indications of pain (e.g. the dog licking at the affected area, for example) almost immediately. You may even be able to see the bite’s puncture marks.

The symptoms will vary from animal to animal and depend on the potency of the venom. The first symptom will likely be a sharp pain at the location of the bite, followed later by fever, weakness, and muscle and joint tremors and pain.

As the neurotoxin progresses through the dog’s body, you’ll notice the animal growing increasingly excited and anxious. Its muscles may become rigid, and it might vocalize loudly in response to the severe pain in his back, chest and abdomen. The animal may show a lack of coordination and be unable to stand. It may also experience increased blood pressure and heart rate, respiratory collapse due to abdominal muscle paralysis, and seizures. Death can result if the animal is not quickly given anti-venom treatment.

Pet with Spider Bite – What to Do:

  1. Check for swelling – if your pet has been bitten by a spider if you see inflammation on parts that have few or no hair at all. Check your pet’s paws, joints, muzzle and stomach. Although this doesn’t automatically mean that it is a spider bite, there is a good chance that it is, since spiders love to sting animals in exposed areas of the skin.
  2. Abnormal lesions – Brown recluse bites are large and have a mucous-like formation on the skin due to the rapid infection of the venom. If not treated immediately, this could be very dangerous, even fatal for your pet. It usually looks like a blister.
  3. Fur loss – Examine your pet’s body and see if there is a noticeable loss of fur in patches. This is one of the signs that a spider has bitten your dog and probably the location where the spider has bitten your cat or dog.
  4. Fever and joint pain – Other signs that your pet has a spider bite are fever and joint pains. You can easily do this by observing if your cat or dog is whimpering whenever he sits, stands or lies down. Lack of interaction, irritability and abnormally warm body temperature will show that your pet has a fever and is definitely not feeling well.
  5. Paralysis and spasms – Black widow bites are very harmful to your pet because they can cause severe reaction. A cat will drool excessively when bitten by this spider. Other symptoms are paralysis, very painful muscle spasms and seizures. The symptom itself is pretty much like a sudden epileptic occurrence.

Widow and Redback Spiders – Cats and Dogs

The female black widow or redback spider (in Australia) is recognisable by its black body with prominent red stripe on its abdomen. Females have a body length of about a centimetre while the male is smaller, being only 3 to 4 millimetres long.

Just like us, cats and dogs can fall victim to a widow or redback bite. Bites are seldom fatal in dogs unless bitten several times, however cats are more susceptible to the venom and can readily die if not treated.

Redback spider bite symptoms for both cats and dogs:

– Intense pain at the bite site
– Restless & Distressed
– Breathless
– Muscle weakness
– Muscle tremors
– Paralysis and Death (particularly in cats)
– Vomiting and diarrhoea may occur.
– Cats are often bitten on the tongue; the tongue will often protrude from the mouth.

If you suspect your dog has been bitten by a red back spider it is important that you have them checked by their vet.  However, if your cat is suspected of being bitten you should contact your vet without delay. Red Back antivenin is generally very affective in saving them if you don’t delay.

Information – Charleville Vet Surgery

Wolf Spider Bites in Dogs

Dogs can be badly affected from the bite of a wolf spider and their have been reports of death occuring. A bite is not easy to detect because of their fur. You should check the legs, face, neck and belly. If your dog has been badly bitten, it could go into a shock.

Bite Symptoms:

Your dog may also show other signs like sensitivity to the venom, seizures, nausea and vomiting, face scratching, agitation and rush. The following are other symptoms that you would see in your dog after the bite.

  • Diarrhea
  • Trembling
  • Sometimes death
  • Itch

Spider Bites in Cats

Spider bites are reportedly rare in cats, but spiders can be fun “toys” for a cat and some spiders’ bites are dangerous. What are the symptoms of spider bites in cats? Itchy, red welts can be raised by any insect bite, but what about those dangerous spiders—brown recluse or black widow? Immediate medical attention is the best chance your cat has of surviving a bite from a highly venomous spider, but first you have to be aware that your cat has been bitten. .

The Facts: 

Cat skin is thicker than most spiders’ fangs are long; only three types of spider in North America are known to cause serious damage with a bite: the black widow, one of many species of widow spider; the brown recluse, one of many spiders known as “brown spiders”; and the hobo spider. Symptoms arise long after the spider has bitten and left. The bite itself is painless. To discover which type of spider, you have to analyze the symptoms.

Types of Bites:

Black Bellied Wolf Spider (Tasmanicosa godeffroyi, family Lycosidae):
Fatal to dogs and cats within 1 hour. (Info – Australian Museum)

Widow Spiders
Bites from a spider with —the widow spiders—will cause muscle cramping. This venom causes over-production of neurotransmitters, bringing on seizures in major muscle groups. The cat’s muscles and abdomen will feel rigid, and breathing will become rapid and shallow. The diaphragm is a major muscle essential to breathing. Death can occur from seizure of this muscle and effects of the toxin on the heart.

Brown Recluse and Hobo Spiders
Bites from a spider with necrotic venom, such as the brown spiders and hobo spider, cause the breakdown of cellular structure. Tissue damage begins at the bite site, showing as an itchy, red lesion, often with a white ring surrounding it. Bluish or bruised-looking coloration indicates tissue death. This visual cue can go unnoticed until the venom begins working on deeper tissues.

Time Frame:

Once the cat has been bitten, symptoms may appear anywhere from 30 minutes to 6 hours later. In the case of a brown spider or hobo spider, the tell-tale white “bull’s eye” pattern will appear within 4 to 8 hours. Symptoms of deeper tissue damage such as fever, vomiting, shock, kidney failure and internal bleeding may take 3 to 4 days to show. Muscle rigidity and pain from a black widow bite will last several days in a healthy adult cat and may take up to a month to fully clear. If the cat is going to die from a widow spider bite, experts say death can happen within one day of the bite.


Widow spiders are common worldwide and can be found under things such as houses, woodpiles, rock piles, and inside garages and sheds. Species found within the United States include the common black widow, the western black widow, the red widow and the brown widow. Brown recluse spiders belong to a group of ten brown spider species in North America and are found from the south central Midwest to the Gulf of Mexico. Less familiar brown spider species occupy the Desert Southwest. Hobo spiders can be found in the western United States.


A restless cat who licks a particular spot more than usual or shows other signs of unusual behaviour related to itchiness should be checked carefully. Watch the cat closely for further warning signs. Look for a red, irritated patch of skin. These symptoms can indicate many issues, but if further symptoms appear such as the “bull’s eye” pattern, seek veterinary attention immediately. With a widow spider bite, the cat may not indicate anything is wrong until muscle rigidity and paralysis set in, along with rapid, shallow breathing. Symptoms from hobo spiders, brown spiders and widow spiders are not limited to the site of the bite and quickly spread throughout the body.


Be aware of the presence and possibility of venomous spiders in your area. Block your cat’s access to spider-prone areas such as woodpiles and sheds, or keep your cat indoors. Spiders can come inside the house as well. If you choose to remove individual spiders yourself rather than calling an exterminator, do so carefully—the spiders’ bites cause the same unpleasant symptoms in humans. Your veterinarian can administer pain relief and muscle relaxants to help your cat weather the effects of widow spider bites, especially if caught early. Antivenin is prohibitively expensive and is rarely administered, reserved for at-risk young or elderly individuals, but it can help in some cases. Full recovery can take up to a month. Application of ice packs to the bite location of hobo spider or brown spider bites can slow the venom’s symptoms. Veterinarians will often use corticosteroid injections to slow or stop the tissue damage. The earlier this is administered, the better the chances of the cat’s recovery. Drugs used for leprosy in humans can effectively fight necrotic spider venom. The cat may be put on antibiotics to combat secondary infections.

Information –

Spider Bites in Horses

Symptoms of a spider bite in a horse may start out as a pea-sized lump in the centre of a 3-inch-high soft swelling on the side of your horse’s chest. It will resemble a fly bite or bee sting The hair covering the lump may fall out, leaving a 50-cent-piece-sized bald spot. The spot will be pink, raised about a quarter-inch, and very sore. (Your horse steps away and/or pins his ears when you touch it.) The horse will rub it furiously on any available surface. Over the next few days, the lump will gradually grow to a hard, fist-sized knot which will apparently be still very itchy, because your horse rubs it incessantly and a thick, greenish-yellow liquid will come out.
You should:

1. Call your veterinarian as soon as possible.

Why: Although this isn’t an emergency requiring urgent care, your horse needs prompt veterinary attention. The history of this particular lesion and your horse’s obsession with scratching it-despite your good care-suggest that it’s the result of a toxic spider bite, such as from a brown recluse or black widow. Spider bites are a common occurrence in autumn. That’s when many creatures move indoors for the winter, often resulting in horses and arachnids becoming unwitting roommates.

When tissues come into contact with spider venom, they’re severely damaged and quickly die, resulting in an abscess. In this case, the abscess is a capsule of inflamed tissue clenched around a liquefying hotbed of dead, dying, and infected muscle, connective tissue, and nerve endings. The pain and itch can be intense, as evidenced by your horse’s behaviour.

If diagnosed earlier-and the type of spider confirmed-then quick and aggressive veterinary treatment, possibly including antivenin, can limit the tissue damage by blocking the destructive action of the venom. Once the wound becomes necrotic however, the venom has done its damage and is long gone. Your only option to resolve the problem with the least possible scarring will be surgical removal of all affected tissue.

2. Keep your horse from rubbing the area.

Why: Additional trauma from scratching and rubbing can enlarge the abscess by forcing its contents into adjacent tissues. Your horse’s efforts to scratch the itch may also bruise and/or abrade the affected area.

How: Keep your horse in crossties under close supervision, occupy him with hand walking, or confine him in a small, tree-free paddock with electric fencing. Or, consider hauling him to your vet’s hospital facility, if available, so your horse can be put in a padded recovery stall and/or sedated to keep him from rubbing until his appointment.

3. Withhold food.

Why: Your vet might opt to perform surgery under a short-acting general anaesthetic, and there’s less chance of complications if your horse has an empty stomach.

How: Pick up all hay and feed and/or bring your horse in from pasture. If he’ll be in a stall and is prone to eating his bedding, strip it out. Make sure he has free access to fresh water at all times, so he keeps himself well hydrated.

4. Be aware of spiders.

Why: To lessen the likelihood of a repeat occurrence.

How: Clean out all undisturbed corners of the barn and any other sheltered areas where your horse spends time, to find and eliminate spider nests. It doesn’t have to be perfect like NY cleaning experts would do. Cleaning services scrub and sterilize every corner of a room but that’s not necessary in a barn. Then keep these areas clear to discourage spiders from setting up housekeeping. Woodpiles are favourite habitats for spiders, so if there are any in or near your horse’s shed, remove them. (Wear heavy gloves, long sleeves, and long pants-and watch for angry arachnids.) Also, check hay flakes by giving them a good shake before letting him dig in.


Good. Thanks to a rich blood supply and the good drainage effects of gravity, this particular location should heal normally once all affected tissue has been removed. Your vet may decide to leave the wound open, rather than stitch it closed, so it can drain optimally. Despite how ugly this looks at first, the crater usually fills with healthy, pink tissue within a couple weeks, and within another week or 2, the skin grows in from the edges, leaving little or no scar.

Info: Karen Hayes – Idaho-based equine practitioner.

Pets and Spider Bites

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