Canine roundworms live in a dog's small intestinal tract. Dogs can become infected in one of several ways, including ingesting eggs in soil, ingesting a rodent such as an infected mouse or squirrel, while developing in its mother's uterus, or after birth, while nursing from an infected dog. Roundworms can be successfully eliminated from dogs.
Common name: Roundworms
Scientific names: Toxocariasis, Ascariasis.
All dogs can be infected with roundworms, but puppies under 6 months old are most commonly infected.
Roundworms are a very common intestinal parasite. A survey of national shelters found that 36 percent of dogs nationwide and 52 percent of dogs in southeastern states were infected with parasites.
Roundworms are found worldwide, although a higher incidence of roundworm infections is found in the southeastern United States.
Clinical signs (primary, most to least frequent, scientific term, synonyms)
Silent infection (no clinical signs noted), Diarrhea, Potbellied appearance (especially in puppies), Vomiting.
Clinical signs (secondary, most to least frequent, scientific term, synonyms)
Dull, dry hair coat, Intussusception (the telescoping one part of the intestine within another part, causing an obstruction), Pneumonia, Aberrant larval migrans (the larval worm gets ‚Äúlost‚Äù and causes injury to an organ such as the brain or the eyes).
Causes (scientific, common term)
Toxocara canis (dog roundworm), Toxascaris leonine (roundworm), Bayliascaris procyonis (raccoon roundworm).
Organ systems affected (most to least affected)
Small intestine, Hair coat, Aberrant organ damage (especially the brain or the eyes), Diagnostic test, Fecal flotation.
Infection from other parasites (hookworms, whipworms, Giardia or coccidia), Canine parvovirus, Intestinal obstruction from a foreign body (such as a rock, a toy, etc.).
Canine roundworms live in a dog's small intestinal tract. Ascariasis and Toxocariasis are the medical terms for a roundworm infection. There are three different species of roundworms that can infect dogs: Toxocara canis, Toxascaris leonine and Bayliascaris procyonis. All dogs can be infected with roundworms, but puppies under 6 months old are the most commonly infected. Roundworms are found in all 50 United States but are most prevalent in the southeastern United States.
A survey based on fecal floatation revealed that 36 percent of dogs nationwide and 56 percent of dogs in southeastern states were infected with one or more parasites that can also infect humans. A fecal flotation is a diagnostic test to find parasite eggs in feces. Dogs can be infected with roundworms in several ways. The most common is transplacental transmission, or when the worms in a pregnant dog cross the placenta and infect the unborn puppies. Puppies can also become infected by nursing from an infected mother dog. This is known as transmammary infection.
Ingesting a rodent infected with roundworms can also cause infection. After weaning, dogs are most often infected by eating soil contaminated with roundworm eggs or by eating feces. Most infections are mild and do not produce clinical signs. Heavy worm burdens can lead to diarrhea, potbellies, or a dull, dry hair coat. Dogs may vomit worms. Worms can cause an intussusception, in which the intestine telescopes, leading to an obstruction.
Rarely, the larval worms do not go to the intestine but migrate to other parts of the body. This can cause damage to organs such as the brain or the eyes. Especially in puppies, pneumonia and coughing sometimes occurs if a large number of larval worms are in the lungs. Roundworms can be transmitted to humans, especially children. In humans, the disease is known as visceral larva migrans. The worms commonly infect the eyes, brain, liver and lungs. The damage to eyes and to other organs is permanent.
A clean environment is most important to prevent infection. Pick up feces daily. Train dogs to eliminate in areas not frequented by children. Teach children proper hygiene.
A veterinarian will perform a fecal flotation to diagnose roundworms or other intestinal parasites. The veterinarian will prescribe a dewormer to treat roundworms and any other parasites. Most infected dogs will require more than one worming. Breeders should consult with their veterinarian about the best wormer for a pregnant or nursing dog. For dogs on heartworm preventive, many of the treatments control roundworms and other parasites as well as heartworms.
Diagnosis and an appropriate deworming plan for an individual animal should be made by a veterinarian. Many pets have multiple parasites, and the appropriate wormer or interval of worming will not be the same for all dogs. Owners should remove all fecal material daily to decrease the risk of infection to the dog and to humans.
Most dogs infected with roundworms will have minimal problems. Routine deworming will prevent most problems.
Taylor, K. Roundworm Infection. In: Cote, E, ed. Clinical Veterinary Advisor: Dogs and Cats. Saint Louis: Mosby, 2007; 979-80.
Blagburn, BL, Lindsay DS, Vaughan JL, et al. Prevalence of Canine Parasites Based on Fecal Flotation. Comp Cont Educ Vet Pract 1996; 18: 483-509.
Parsons JC. Ascarid Infections of Cats and Dogs. Vet Clin North Am Small Anim Pract 1987; 17: 1307-39.
Center for Disease Control Division of Parasitic Diseases. Guidelines for Veterinarians: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats. http://www.cdc.gov/ncidod/dpd/parasites/ascaris/prevention.htm
Charlotte Means, DVM, MLIS, DABVT
Steven Hansen, DVM, MS, MBA, DABVT, DABT
© 2007. The American Society for the Prevention of Cruelty to Animals (ASPCA)