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Roundworm and Your Dog

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Roundworm Basics

Roundworms are commonly diagnosed in puppies,1 and may infect 90% of puppies under three months of age.2 However, infection can occur in dogs of all ages. In a study roundworm eggs were found in 15% of all dogs.3

Roundworm and Your Dog


Roundworm Transmission Methods

Roundworms in dogs are most often transmitted before birth.4 In fact, it is not unusual for puppies only 2-3-weeks-old to have a significant number of worms.5

Otherwise, infection can occur by ingestion of the mother’s milk by a nursing animal.

Older puppies and dogs are most often infected by contacting the feces or ingesting the meat of an infected animal.

Health Risks Posed by Roundworm Infection

Once inside a dog’s body, ingested roundworm eggs hatch and the larvae then migrate to the intestine and become adults. There, they feed, depriving the dog of vital nutrients and, in some cases, block the intestine entirely. Female roundworms can lay more than 100,000 eggs per day.6

Clinical signs can include diarrhea, weight loss and swollen abdomens. Left untreated, roundworms pose a serious health risk, especially for young dogs and puppies.

How to Protect Your Dog from Intestinal Parasites

Important Safety Information:
HEARTGARD (ivermectin) is well tolerated. All dogs should be tested for heartworm infection before starting a preventive program. Following the use of HEARTGARD, digestive and neurological side effects have rarely been reported. For more information, please visit

Click here to download full prescribing information.
1) CAPC Recommendations. Accessed October 13, 2010.
2) Schantz PM. Zoonotic ascarids and hookworms: the role for veterinarians in preventing human disease. In: Emerging vector-Borne and Zoonotic Disease, The Compendium Suppl 2002;24(1):47-52
3) Blagburn BL, Lindsay DS, Vaughan JL, et al. Prevalence of canine parasites based on fecal flotation. Comp Cont Ed 1996;18(5):483-509.
4) Parsons JC. Ascarid infections in cats and dogs. Vet Clin North Am Small Anim Pract 1987;17:1313-14.
5) Epe C. Biology of Intestinal Nematodes Ascaridal. Vet Clin North Am Small Anim Pract 2009;39:1092.
6) Lloyd S, Toxocarosis In: Palmer SR, Soulsby EJL, Simpson DIH, eds. Zoonosis. New York: Oxford University Press, 1998;842.

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