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Dog Worms: Canine Intestinal Parasites


Worms, or intestinal parasites, can affect all puppies and dogs. Intestinal parasitism is one of the most common conditions in clinical veterinary practice and is frequently identified in dogs.

Types of Dog Worms

Many types of intestinal parasites infect dogs. The most common canine intestinal parasites in the United States are roundworms (Toxocara cati or Toxascaris leonina), hookworms (Ancylostoma caninum, Ancylostoma braziliense, Uncinaria stenocephala), whipworms (Trichuris vulpis), and tapeworms (Taenia spp., Dipylidium caninum, Echinococcus multilocularis, Echinococcus granulosus). Several intestinal parasites can infect puppies through lactation from an infected mother, and this is why it is important to treat puppies with de-worming medications throughout puppyhood.

How Are Dogs Infected with Intestinal Parasites?

Dogs are infected with roundworms, hookworms, whipworms, and tapeworms after ingestion of infective eggs and larvae from the soil and the environment. They can also become infected by ingesting the tissues and intestines of prey animals or tapeworm proglottids (infectious tapeworm segments full of eggs that look like pieces of rice). Ingestion of infected fleas can result in tapeworm infection in dogs, and all dogs diagnosed with intestinal worms should be treated for flea infestation.

Clinical Signs of Intestinal Worms in Dogs

Dogs infected with intestinal parasites may demonstrate vomiting, diarrhea, lethargy, weight loss, anemia (low red blood cell counts), respiratory signs (breathing problems, cough), or an enlarged belly. Puppies can become particularly ill. Some dogs may never show any symptoms of infection, while others can become very ill. Owners may see worms or proglottids passed in the vomitus or stool or emerging from the anus (roundworms and tapeworms are the only intestinal parasites visible to the naked eye). Some dogs will exhibit itching in the anal area and drag their rear quarters against rugs and carpets, but this is fairly rare.

Diagnosis of Intestinal Parasites in Dogs

Intestinal parasites are most commonly diagnosed by identification of eggs in a dog's fecal sample. This is why your veterinarian requests a yearly stool sample for evaluation.

Treatment of Worms in Dogs

Several medications are available that effectively treat intestinal parasites in dogs. Treatment usually includes a single treatment followed by several follow-up treatments to kill all immature worms in the body. There are many different de-worming medications available throughout the United States (pyrantel pamoate, fenbendazole, praziquantel). Each medication treats different worm(s). It is, therefore, imperative that you immediately contact your veterinarian if you suspect that your dog has worms. The veterinarian will identify the worm species and prescribe appropriate treatment. Over-the-counter de-wormers are usually not helpful.

Prevention of Intestinal Parasites in Dogs

The best way to decrease the likelihood of intestinal parasites in your dog is the use of regular heartworm preventative medications. Most (but not all) of these medications de-worm your dog for common intestinal parasites as well as protect against heartworms. Dogs should also be treated with flea preventative medication. These medications are all available from your veterinarian. Please consult your veterinarian to determine the most effective protocol for your dog's parasite prevention based on the area in which you live and your individual dog's circumstances. Some of these parasites can infect humans, and this is another reason to emphasize parasite prevention, particularly in families with young children and immunocompromised family members.

Note: Before beginning heartworm medication, dogs must be tested to ensure that they are not already infected because administering certain heartworm preventatives to a dog that is already infected with heartworm can result in serious illness and even death.

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