Roundworm lifecycle in dogs

Learn about the different stages of the roundworm lifecycle in dogs.

The worm that returns for more

It’s quite common for dogs around the world to deal with roundworms. But young pups often experience the most severe effects of the resulting disease from a roundworm infection. And worst of all, your dog can become infected again and again. In dogs, roundworm infection* is associated with failure to gain weight, diarrhea, poor hair coat and a potbellied appearance.
*T.canis only

The roundworm lifecycle

The incubation period for roundworm is around 4-6 weeks, meaning it can be over a month between ingesting the roundworm and them passing eggs in their stools which may infect other animals.

Infographics Picture

  • 1

    Adult worms lay eggs in the dog’s small intestine.

  • 2

    Eggs are passed then passed in the dog's feces.

  • 3

    Eggs develop in the environment and become infective approximately 1 week after being passed in feces.

  • 4

    Embryonated eggs can be ingested by transport hosts, such as field mice or earthworms, who become carriers of larvae.

  • 5

    The dog ingests larvae through the tissues of the transport host.

  • 6

    Larvae migrate through the dog’s liver and lungs to the small intestine, where they mature into adult worms.

  • 7

    Larvae are released from infective eggs and mature in the dog's intestinal tract.

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Would you know what to look out for? Read up on the signs of intestinal worms.

How does a dog get worms?

See where your dog is most at-risk of contracting different worm types.

Whipworm lifecycle

Learn more about the whipworm lifecycle.


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.

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.

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