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Healthy Dogs

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Roundworms in Dogs

Roundworms, also known as ascarids, are parasites that live inside and feed off an animal’s intestines.

They’re usually white or light brown and a few inches long. (They look like spaghetti.) If your dog has roundworms, you may notice them in his poop or vomit.

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Some dogs don’t show symptoms of being infected, but many do. Here’s what to look for:

  • Pot-belly
  • Weakness
  • Diarrhea
  • Vomiting
  • Belly pain
  • Dull coat
  • Weight loss
  • Roundworms in poop or vomit

If you see these signs, take your dog to the vet. He'll test a sample of your dog’s poop and begin a set of treatments if necessary.


There are many safe and effective deworming drugs. They include fenbendazole, milbemycin, moxidectin, nitroscanate, piperazine, and pyrantel.

Your vet will give your dog one to three doses at first, which will kill the adult worms. Your dog will get follow-up doses to kill any new worms that weren’t fully developed when the first doses were given.

Because it’s so common in puppies, many vets deworm pups when they’re 2-3 weeks old just to be safe.

Even after your dog is treated, he should get regular fecal exams. For puppies, that’s two to four times a year. For dogs 1 year or older, it’s one to two times a year.

How Dogs Get Roundworms

These parasites are common. Puppies have the highest risk of getting them and becoming sick.

Your dog may get them from:

  • His mother. If your puppy’s mother is infected with roundworms, she may pass them before he’s born. Or he may get them by drinking her milk.
  • The environment. Your pup can get roundworms if he eats roundworm eggs that come from another animal’s poop, or if he eats mice or other small animals that are infected.

This is how the cycle continues: After your dog swallows the eggs, they hatch and turn into larvae. The larvae then spread through your dog’s liver and up to his windpipe. Next he coughs and then swallows the larvae. That’s how they get into his intestine, where they can grow into adult worms. Then they lay their own eggs, which continues the cycle.

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