This photo shows round worms in feces that came from a six-month-old puppy. Copyright Dogs Forever 2013

Worms in Dogs: 
Prevention & Treatment

Worms in dogs—it is a health issue that many parents contend with at least once in their furry child's life. But as you will read throughout this web site, a healthy dog has a strong immune system that enables him/her to fight many illnesses and diseases. This does not mean a healthy dog will never become ill, but it does mean the chances of becoming ill are reduced. And if a healthy dog does fall ill—such as contracting intestinal parasites—he/she is more likely than an unhealthy dog of making a good recovery.

Snapshot: Worms in Dogs
Here's a quick overview if you're in a hurry. Come back later when you have time to read the complete guide to "worms in dogs."

  • Symptoms: Depending on the type of parasite, the dog may have diarrhea (watery or bloody), the stool may be very dark, or it may be well-formed but the worms can be seen in it. Worms can look like rice or spaghetti, but not all worms can be seen in feces.A very thin dog may have worms. A puppy with a fat belly is likely filled with worms. In fact, most puppies have some type of intestinal parasite and need to be dewormed.
  • Causes: The "big four" worms in dogs are roundworm, tapeworm, hookworm and whipworm. A dog may become infected by eating fleas, eating prey, coming in contact with infected soil or eating contaminated feces--the method of infection varies by parasite.
  • Treatment: Oral (liquid or pill) or injectable dewormers are used and often repeated in 30 or 70+ days depending on the type of parasite.
Hook worms in dogs are less common than tape worms and round worms. They are most often found in dogs living in the southern U.S. in unsanitary conditions.

Worms in dogs may cause diarrhea or the stool may look normal. Sometimes worms can be seen in the feces, but this is not always the case. A dog with worms may also appear thin and unable to gain weight, since worms compromise a dog's ability to properly digest and "use" the nutrition in his food. Worms in dogs may also cause anemia, in which case the infected dog may act tired.

Here's how to identify worms in dogs, taking a look at the "big four" parasites:

  • Roundworm:
  • This parasite looks like white spaghetti several inches long. It may be seen in the stool or, when a large number of worms are present, the dog may vomit whole worms.

  • Tapeworm:
  • Tapeworms grow in the dog's small intestine. Eventually egg-filled segments of the tapeworm leave the dog's body and may be seen on his rear-end or in feces. The segments are cream-colored and resemble grains of rice.

  • Hookworm:
  • Hookworms are less common than roundworms and tapeworms. They are often seen in dogs living in areas of the South where unsanitary conditions are prevalent. Left unchecked, this parasite can cause anemia. Hookworms can be transferred from a female dog to unborn pups and due to their fragile immune system, this parasite is often fatal to puppies. Feces sometimes look black and have a thick consistency.

  • Whipworm:
  • This parasite lives in the dog's large intestine and is rarely seen. Often whipworms will not be a problem unless a large number set up house in the dog's colon. This can lead to bloody, sticky diarrhea or very watery diarrhea.

What causes worms in dogs?

The causes of worms in dogs vary. For instance:

  • Roundworm:
  • Dogs can become infected when they eat the eggs of a roundworm. These eggs travel out of the feces of a contaminated animal to the ground, where they incubate. A dog may eat the worms while sniffing or digging in the dirt or by eating the feces of an infected animal. (Ugh! Our furry friends can have some pretty disgusting habits!)A dog can also become infected when eating prey that is carrying worms. This parasite is not transferred through feces.

A heavy load of worms in dogs can lead to pneumonia or obstruction of the intestine.This parasite is often found in puppies and is acquired from the mother dog. A puppy that is carrying a heavy load of worms will have a large belly (see photo) and may also have diarrhea and vomiting.

  • Tapeworm:
  • There are several types of tapeworms that affect dogs. The common tapeworm (Dipylidium caninum)is contracted when a dog eats a flea, which transmits the disease or a gopher, which carries the parasite. A dog contracts the less common tapeworm, Taenia Hydatigena, by eating a dead rabbit or deer.

  • Hookworm:
  • This dog parasite is also found in the ground but infects the dog through its skin, at the point of contact where the dog touches feces-contaminated soil.

  • Whipworm:
  • Whipworm eggs are transported from an infected animal's large intestine through feces. Once outside the body, the eggs take up residence in the ground. Within a month they become embryos and are capable of infecting a new host. A dog is infected when he/she ingests whipworm embryos, likely through grooming as they lie on the ground. Whipworms can literally live in the soil for years.


If you suspect your dog has worms, your veterinarian will need to examine a stool sample under a microscope in order to make a diagnosis. Here are some common treatments, based upon the specific intestinal parasite identified.

  • Roundworm:
  • Drontal, Drontal Plus and Panacur are often used as dewormers. These medicines work by relaxing the parasite so it lets go of the intestine wall and is expelled through feces. It's important to remember that worms in migration—those not yet attached to the intestine—will not be affected by the dewormer. That's why it's important to do a follow-up dewormer several weeks later.

    Monthly heartworm preventatives such as Heartgard Plus, Interceptor and Sentinel offer the added benefit of deworming against roundworms.

  • Tapeworm:
  • An adult tapeworm is made up of segments or packets—which is how the tapeworm eggs are passed through the dog's stool. If the segment has not yet broken open at the time of the stool exam, the eggs will not be visible. However, a diagnosis of tapeworm will be made if segments are seen in the stool or on the dog's rear. Both the common and less common forms of tapeworm are often treated with praziquantel, which is available as an injection, tablet or topical.

    Your vet will probably recommend a follow-up treatment in three weeks to ensure your dog is completely rid of the parasite.

  • Hookworm:
  • Treatment for this parasite usually includes one of the following: Mebendazole (sold under the brand Telmintic), fenbendazole (brand name Panacur), pyrantel pamoate (brand names Nemex, Drontal and Strongid T). The medication should be repeated in about 30 days to kill any hookworms that were not in the gastrointestinal tract initially, but were in migration. By the second round of treatment, these worms have completed their migration and are in the GI tract, where they can be killed.

    It should be noted that a puppy may need to have a blood transfusion and an iron supplement in addition to the above medication. While other worms survive by absorbing the host's digested food, hookworms suck the blood of the host (dog/puppy). In the case of a growing puppy, the hookworms are "stealing" the red blood cells he/she needs for healthy development.

  • Whipworm:
  • While most female parasites lay eggs on a continuous basis, the whipworm has a more haphazard routine, laying eggs "once in a while." Because of this, a dog infected with whipworms may test negative. If your veterinarian suspects your dog is infected with whipworms due to symptoms, he may recommend deworming for this parasite. Common dewormers for whipworm are fenbendazole (brand name Panacur) and febantel (sold as Drontal Plus). A second deworming should be done around 75 days because it takes whipworms a long time to mature.

    In some cases, heartworm preventatives with ivermectin, such as Sentinal and Interceptor, may be recommended by your vet to treat whipworms.

My Experience

Worms in dogs—fortunately this is not something I have had to contend with in my own dogs, except for Max. As I noted on the page about canine diarrhea, Max was from a Chicago pound and was deathly thin. He had worms. Thankfully, he overcame his maladies and lived with us for many years.

But there is a very true lesson here: Healthy dogs will usually not contract worms. Worms are opportunistic parasites. They seek a weakened host (dog). If you adopt a dog from a shelter or animal rescue, be sure to monitor his/her stool. If you see any of the symptoms noted above, take your fur kid to a veterinarian.

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