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Roundworms in Dogs

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While a sick dog is always concerning, seeing your puppy throw up or defecating wiggling worms can be especially scary. If this sounds familiar, you might be dealing with roundworms, one of the top three most commonly diagnosed intestinal parasites in dogs, along with whipworms and hookworms (1). 

If you suspect your dog might have worms (or you’ve found them already), here’s what you need to know, from early signs of roundworm in dogs to diagnosis and treatment.

What Are Roundworms in Dogs?

dog roundworms

For dogs, roundworms are often a fact of life. They’re such a common occurrence that nearly all dogs deal with them at some point in their lives, most often as puppies.

Adult roundworms live inside your dog’s digestive tract, though immature roundworms migrate throughout her body over time. White to light-brown and a few to several inches long, roundworms look similar to spaghetti (and yes, you may find roundworms in dog poop or vomit). 

What Causes Roundworm in Dogs?

Dogs of all ages can contract roundworms through their environment, by eating or playing with contaminated poop, dirt, plants, or other animals like mice or birds. After your dog eats roundworm eggs with the infective larvae stage, they grow and spread through her liver and up her windpipe, which causes her to cough and swallow them. When they reach her intestine, they grow into adult worms and lay eggs, which she poops out—re-contaminating your yard, the dog park, or wherever she goes to the bathroom. 

Often, though, puppies come into the world with roundworms already, contracted through their mother’s placenta, says Dr. Amy Stone, a clinical assistant professor and chief of the primary care and dentistry service at the University of Florida College of Veterinary Medicine. How, exactly? Well, even if a dog is properly treated for roundworm and otherwise healthy, dormant larvae can stay in her body tissues for the rest of her life. Then, when she becomes pregnant, roundworms can “reactivate” to potentially infect her and her pups.  

An important note: Humans, too, can contract roundworms from dogs’ poop or contaminated areas. Unfortunately, serious health problems can follow, especially in young children, the elderly or those who are immunocompromised. For this reason, pick up your dog’s poop as soon as possible, wash your hands carefully, and keep your kids from digging around in areas where dogs may have used the bathroom (2). 

Symptoms of Roundworms in Dogs 

While dogs can have roundworm infections without any symptoms, there are some signs of roundworm in dogs to be aware of. For one, as roundworms irritate your dog’s stomach and intestines, they might cause diarrhea or vomiting. 

Puppies with serious roundworm infections may throw up a mass of large, wiggling worms (3). Again, this can be a disturbing sight for pet parents. 

As her roundworm infection progresses, your dog might seem weaker and lose weight due to malnutrition (as roundworms feast on partially digested food in her intestines). If enough adult roundworms accumulate, your dog or puppy can also develop a pot-bellied appearance.

Diagnosis of Roundworms in Dogs

dog at vet

If you find what could be roundworms in dog poop or believe your pup is showing other signs of roundworm in dogs, your veterinarian will take a fecal sample and look for roundworm eggs under a microscope. As roundworms are so common in puppies, this fecal test is typically included in your dog’s first veterinary appointment, along with deworming medication, says Stone. 

In some cases, the sample is sent to the lab for additional testing. There is also a new test available now that can detect antigens (proteins produced by the worms) from the worms in the feces. 

Roundworm Treatment for Dogs

As concerning as roundworm in dogs can be, roundworm treatment is typically simple and affordable. Because roundworms can be persistent, though, your veterinarian should keep up regular fecal exams to check for them (two to four times in the first year and one to two times per year afterward), says Stone. 

For your dog’s roundworm treatment, your veterinarian will prescribe a deworming medication, followed by a monthly parasite protection medication to help prevent future roundworm infections. 

Do not be alarmed if you see worms in your dog’s stool after deworming. It is common for dogs to pass worms post-treatment—it’s normal and means the product is working.

Roundworm Medicine for Dogs

Some common deworming medications like milbemycin oxime, fenbendazole, and pyrantel pamoate are commonly-prescribed roundworm treatments. 

As roundworms are so often present in newborn puppies, they should be given routine roundworm treatment (namely, a deworming medication) as soon as they are 2 weeks old. Deworming should be repeated every two weeks until the puppies are 4 to 8 weeks old and placed on a monthly broad-spectrum parasite protection medication that covers roundworms, says Stone. 

For adult dogs, roundworm treatment is the same: deworming medication and a long-term parasite protection medication to keep worms away. Sometimes it may be recommended to just start your dog on a long-term parasite protection medication, as this is a dewormer. In other words, your dog may not need additional medication to clear an infection. 

Using a heartworm preventive that is effective against multiple worms is an easy way to protect your dog. For example, Interceptor® Plus (milbemycin oxime/praziquantel) prevents heartworm disease and treats and controls roundworms, hookworms, whipworms, and tapeworms.

See important safety information below for Interceptor® Plus.

Cost to Treat Roundworm in Dogs

Typically, treatment for roundworm is very affordable and many monthly heartworm preventive medications cover it, says Stone. For a dewormer only, the cost is approximately $10 to $20. You may find it more cost effective to use a monthly heartworm preventive that includes roundworm coverage. 

Roundworm Prevention in Dogs

two Basset Hounds on leashes

In order to protect your dog and other dogs from getting sick from roundworms, pick up her poop as soon as possible to prevent roundworm eggs from contaminating her environment. 

Your dog can encounter roundworm eggs in any location frequented by other dogs or wild canids, such as foxes, coyotes, and wolves. If your dog is one to explore places like forests, parks, and fields (and roll around in dirt and poop from other animals), keep her on a tight leash or in a fenced-in yard to lower her chances of being exposed to roundworm eggs, suggests Stone. 

A healthy dog is a happy dog, so if you suspect your canine companion might have roundworms, be sure to contact your veterinarian. With their help, you’ll get peace of mind, potential treatment, and a goodbye to roundworms in dog poop for good (and really, what more could a pet parent ask for?). 

Interceptor Plus Indications

Interceptor Plus prevents heartworm disease and treats and controls adult roundworm, hookworm, whipworm, and tapeworm infections in dogs and puppies 6 weeks or older and 2 pounds or greater.

Interceptor Plus Important Safety Information

Treatment with fewer than 6 monthly doses after the last exposure to mosquitoes may not provide complete heartworm prevention. Prior to administration of Interceptor Plus, dogs should be tested for existing heartworm infections. The safety of Interceptor Plus has not been evaluated in dogs used for breeding or in lactating females. The following adverse reactions have been reported in dogs after administration of milbemycin oxime or praziquantel: vomiting, diarrhea, decreased activity, incoordination, weight loss, convulsions, weakness, and salivation. For complete safety information, please see Interceptor Plus product label or ask your veterinarian.

Disclaimer: The author received compensation from Elanco US Inc., the maker of Interceptor Plus, for her services in writing this article. 


  1. Drake, J., Carey, T. Seasonality and changing prevalence of common canine gastrointestinal nematodes in the USA. Parasites Vectors 12, 430 (2019) doi:10.1186/s13071-019-3701-7
  2. Toxocariasis FAQs. Centers for Disease Control and Prevention. Retrieved from: https://www.cdc.gov/parasites/toxocariasis/gen_info/faqs.html
  3. Ascarid for Dog. Companion Animal Parasite Council. Retrieved from: https://capcvet.org/guidelines/ascarid/

Interceptor is a trademark of Elanco or its affiliates. 

© 2020 Elanco.  PM-US-19-2132

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