Dog Intestinal Worms

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Even if you don't see worms in your dog's stool, he could be an unwilling host to any of a number of intestinal parasites that threaten his health and can even sicken the people around him.

Who Is Most at Risk?

Four types of intestinal worms most frequently infect dogs.

Roundworm are primarily a problem for puppies. They usually pick up these parasites from their mother, either while they are still developing in the uterus or from suckling milk that contains roundworm larvae. Adult dogs can also become infected when they eat a small amount of dirt containing roundworm eggs or eat an infected prey animal (e.g., a rodent).

Hookworms are frequently diagnosed in both adult dogs and puppies. Like roundworms, these parasites can be passed from mother to puppy or through ingestion of dirt contaminated with the eggs, but hookworm larvae in the soil can also burrow through a dog's skin and gain access to his body in that way.

Whipworms most commonly affect adult dogs or older puppies. Whipworm eggs are shed in the feces of an infected dog and can survive in the environment for years. Dogs become infected when they ingest dirt containing the eggs, for example, when they lick their paws.

Tapeworms also tend to be found in adult dogs or older puppies, especially those that harbor fleas. Mature tapeworms in a dog's intestinal tract shed pieces of their body that can be seen by the naked eye. They usually look like squished pieces of rice that can be found, often still moving, around a dog's anus or in his bedding. The parasite's eggs that are contained in these body segments are eventually eaten by fleas which can pass on the infection when they are in turn ingested by a dog or other animal that is grooming itself. Other types of tapeworms that do not rely on fleas as part of their life cycle also exist, so even flea-free dogs can get tapeworms.

Why Owners Should Be Concerned

Intestinal worms can make dogs very sick. Roundworms can cause diarrhea, vomiting, a bloated abdomen, weight loss and poor growth, but some infected animals show no clinical signs at all. Hookworms can also cause diarrhea and vomiting, but because they suck their host's blood at their attachment site in the intestinal tract, they can also lead to a potentially life-threatening anemia. Whipworms typically cause diarrhea, while tapeworms may cause anal irritation and "scooting" when the worm segments wiggle around a dog's hind end.

"If you need to pick out a dewormer yourself, use one that kills the parasites most likely to be infecting your dog."

People can also become sick when they are infected with canine intestinal parasites. The biggest problems revolve around hookworm larvae that invade through the skin and roundworm larvae that migrate to the eye or other parts of the body. One type of canine tapeworm can also cause cysts in the human body. Keeping your dog free of intestinal parasites and picking up his feces protects both canine and human health.

Veterinary and Home Care

There are two ways deal with the threat of canine intestinal parasites. The first is through the use of fecal examinations. A veterinarian will look at a sample of feces that has been mixed with a particular type of solution that causes worm eggs to float to the surface. This helps diagnose exactly which parasites are present, including some like Coccidia and Giardia that are not technically worms and are not killed by traditional dewormers. Your vet can then pick exactly the right medication to treat your dog.


Fecal examinations are an absolute necessity for puppies and any pet that has diarrhea, vomiting or other gastrointestinal symptoms. The downside of fecal examinations is that they are sometimes falsely negative, meaning that no eggs are seen even when parasites are present. For this reason, your veterinarian may run several fecal examinations over a period of a few days or elect to deworm even if the tests are negative.

Pet owners and veterinarians may also elect to deworm without running a fecal examination. The positives of this approach include simplicity and the fact that dogs that would have a false negative fecal exam are still dewormed. The negative side is that some dogs that don't need to be dewormed will be and some parasites that are not killed by traditional dewormers may go undiagnosed.

If you need to pick out a dewormer yourself, use one that kills the parasites most likely to be infecting your dog. Some types of heartworm preventatives also help protect against intestinal parasites. Look at the label to see if this is the case. Whichever pet meds you choose, make sure to follow the instructions closely. Many products require multiple doses to completely eradicate the parasites. When in doubt, ask your veterinarian which product is right for your dog.

The above is provided for information purposes only and should not be used for the diagnosis or treatment of any condition. This information does not cover all possible variables, conditions, reactions, or risks relating to any topic, medication, or product and should not be considered complete. Certain products or medications may have risks and you should always consult your local veterinarian concerning the treatment of your pet. Any trademarks are the property of their respective owners.

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