Black Widow Spider Bites in Cats

Very young and very old cats are more difficult to treat than cats with strong immune systems.
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The black widow spider is an arachnid rock star when it comes to venom. While there are other venomous spiders, the black widow's bite is deadly because the symptoms are insidious, the bite difficult to see and the diagnosis difficult to make. Treatment is a challenge as well.

That Telltale Hourglass

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The black widow spider is not the biggest or scariest looking spider, but it is among the top 10 most dangerous spiders, according to Outdoor Life. Venomous animals have a warning -- a bright, colorful shape or stripe -- to let other animals know not to start any trouble. The black widow has a red hourglass shape on its back. The black widow was once responsible for human fatalities before the development of an anti-venom. Since their favorite haunt is the outhouse and everyone has indoor plumbing now, people are no longer victims, but critters who hang around wood piles or venture into the woods, such as cats, still are.

Not So Clear but Present Danger

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Cats love to play with their prey, and spiders are readily available bat-about toys. Many times, kitty will ingest the spider when she tires of playing with it, an action that, incredibly, may save her life. Black widow spider bites are difficult to diagnose. Unlike the brown recluse or the brown widow spider bite, which causes an obvious wound, the black widow injects a neurotoxin. The bite is usually too small to see with the naked eye. So unless the vet knows for sure the cat has been bitten, he can't design an effective treatment plan. Since vomiting is a symptom of a black widow spider bite, if the cat has eaten the spider and then vomits it up, it takes the guesswork out of what's wrong with the cat and, more importantly, the species of the sneaky spider.

What to Watch For

Don't rule out a black widow spider bite if your cat is a strictly indoor cat; these tiny terrors are not above breaking and entering. If your cat does spend time outdoors, the chances of a black widow bite are elevated. The symptoms include vomiting, paralysis, shortness of breath, lowered heart rate, ataxia (inability to stand), drooling and diarrhea. The bite of a black widow is very painful so your cat may be crying or howling.

Diagnosis and Treatment

There is a black widow anti-venom for veterinary use but it's costly, and most vets don't keep it on hand. Your vet will begin to treat the symptoms while searching for the site of the bite, if suspected. The vet will want to perform some blood and fecal tests, and it's advisable to bring any products of diarrhea or vomiting with you. The treatment involves keeping the cat comfortable with muscle relaxants, respiration assistance and pain medications. Unfortunately, the prognosis is not good, especially in cats who are immunocompromised such as older cats, cats with chronic diseases and very young cats.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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