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.
Some dogs don’t show symptoms of being infected, but many do. Here’s what to look for:
- 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.
Roundworms spread easily. One roundworm can produce up to 85,000 eggs a day. But you can do a lot of things to ward them off.
- Deworm your puppy when he’s young. The best time to start is before he’s 3 weeks old.
- If your dog is a female, treat her before she breeds and again during pregnancy.
- Keep things clean, including the areas where he eats, sleeps, and plays. Throw away his poop properly. Clean up after him in your yard and also in the park. Don’t let your dog use a playground or sandbox as a litterbox.
- Keep your dog away from small, wild animals. They can carry roundworms. Consider keeping him on a leash or in a fenced yard.
- Give your dog drugs to prevent heartworms. Many have ingredients that also prevent roundworms.
- Talk to your doctor about possibly deworming your dog every so often if he’s at high risk of an infection.
Risk to Humans
It’s rare, but roundworms can cause problems in people. If you have contact with dog poop or soil that’s contaminated, you may get an infection. That can lead to eye, lung, heart, and neurological problems.
Kids have a higher risk and may get infected by ingesting eggs that are in soil or dog poop. Keep them away from areas where dogs have used the bathroom. Be sure they wash their hands regularly.
Companion Animal Parasite Council: “Roundworms,” “Ascarid.”
Cornell University College of Veterinary Medicine Baker Institute for Animal Health: “An Overview of Canine Roundworm Infections.”
The Merck Veterinary Manual: “Roundworms in Small Animals.”