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Intestinal Parasites in Dogs

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Eliminating and controlling intestinal parasites is an important aspect of preventive medicine. Untreated, parasitic infections in dogs can lead to serious digestive issues or other health complications. 

The more common intestinal parasites are hookworms, roundworms, tapeworms, and whipworms. Several non-worm parasites can infect dogs. These include CoccidiaGiardia, and Spirochetes. All of these intestinal parasites can be effectively diagnosed, treated, and prevented with the help of your veterinarian.

As different as each may be, intestinal parasites have a common agenda: to cause discomfort and disease in your pet and your family. Here is an overview of these internal problem makers so you will know what they are, what they can do, and how we can stop them.

Intestinal Worms

As their name suggests, intestinal parasites reside within the lower digestive tract, or the intestines, of their hosts. Larger worms are visibly detectable in a dog’s stool, while other worms—or their eggs—are so small they can only be seen under a microscope. The health issues that different intestinal worms cause are many and varying.

Cause and Symptoms

First, it’s important to remember that many dogs show no outward signs of intestinal parasite infection. So, dog owners may not realize their asymptomatic pet is transferring parasites to others. If there are symptoms, here are some general or common ones:

  • Malnutrition
  • Poor coat
  • Lethargy
  • Weight loss
  • Dehydration
  • Diarrhea
  • Vomiting
  • Bloated abdomen
  • Stomach pain
  • Intestinal blockage
  • Blood in stool
  • Anemia
  • Pneumonia
  • (Many dogs display no symptoms at all)

Puppies are especially vulnerable to intestinal parasites. They can also easily contract worms from their mothers. If left untreated, intestinal worms can lead to serious health issues in puppies. So prevention of parasitic infections should start early in a young dog’s life.

Humans, including children, can also pick up certain kinds of intestinal worms. So it’s important not to let your dog’s waste remain in the yard. If worms, or their eggs, are present in the stool, they can contaminate the soil and be tracked throughout your home on shoes and paws. For that reason, always thoroughly clean up and disinfect after your puppy’s accidents, and keep your dog’s environment clean.


Hookworms resemble common ground worms in shape but are smaller and white to pale yellow. They can grow to about one inch in length but can be as small as one-eighth of an inch. Immature, or larval, hookworms live in the soil and can survive there for several months. To grow into adults, they must feed on blood.

Cause. There are several species of hookworms; dogs can be infected by Uncinaria stenocephalaAncylostoma braziliense, and the more common Ancylostoma caninum. Dogs contract hookworms in several ways:

  • Dogs can ingest the dirt that hookworms live in as larvae, either by licking their paws or by eating the soil.
  • Dogs may swallow hookworm eggs after coming into contact with waste from an infected dog (or with soil that is contaminated with the waste).
  • Hookworms can burrow through a dog’s skin, infecting the pet subcutaneously (usually through the feet, which is also how humans typically contract them).
  • Depending on the type of hookworm (Ancylostoma caninum in this case), puppies can contract them from their mother’s milk if she is infected.

Once inside a dog, hookworms make their way to the small intestines where they attach themselves to the intestinal wall. There, they feed on the dog’s blood. A hookworm infestation can consume so much blood that it can lead to anemia in a pet. In a puppy, it can lead to death if not treated. 

Although they are visible to the naked eye, diagnosis of hookworm is usually made under a microscope, by detecting their eggs within a dog’s stool sample. Treatment includes deworming medication that is typically administered twice—once to eliminate the adult population, and then again two to four weeks later to eliminate the younger generation.


One of the most common of all internal parasites is roundworms. Two species infect dogs: Toxocara canis and Toxascaris leonine. They are whitish and look like short strands of spaghetti about 1 to 3 inches long.

Cause. Roundworms can be passed to other dogs and humans, including children. They transfer from dog to dog when their eggs are shed in the waste of an infected pet and then are swallowed by another pet, perhaps after being tracked indoors on shoes or paws. After they hatch, the worms roam free within the intestines.

Symptoms. Roundworm infection in dogs may be indicated by:

  • Digestive upset
  • Bloated abdomen
  • Malnutrition
  • Coughing
  • Diarrhea
  • Vomiting
  • (No symptoms at all)

Treatment and prevention. Roundworm infection in dogs can be diagnosed by your veterinarian. He or she can examine a stool sample for indications of worms. If found, the vet will prescribe a deworming medication to eliminate them. Given the serious discomfort and health risks roundworms create, please seek your veterinarian’s care immediately if signs of infection appear.


Tapeworms are so named because of their flat, narrow, elongated shape. Their bodies are characterized by a series of segments strung together, each segment resembling a small grain of rice. The worms, and their detached segments, can be large enough to be seen by the naked eye.

Cause. Tapeworms, or their eggs, are carried by various animals, including fleas, rodents, and birds. These serve as intermediate hosts of the parasites and facilitate the tapeworm life cycle. Rather than contracting tapeworms from other pets, dogs acquire the worms from one of the intermediate hosts—fleas in most cases.

The tapeworm species hosted by fleas is Dipylidium caninum, the most common type found in canines. Fleas that carry the eggs of the parasites can be ingested by dogs, either when relieving an itch or when eating an animal infested with fleas (or with tapeworm eggs). After swallowing them, the eggs hatch and attach themselves to the dog’s intestinal wall.

Other species of tapeworms in dogs are Taenia and EchinococcusTaenia is carried by rabbits, rodents, and other small mammals. Puppies rarely contract these parasites; they mainly infect adult dogs. Echinococcus is carried by sheep and humans. It is a smaller variant of tapeworm—measuring about one-quarter of an inch long—and develops inside cysts within its host’s organs.

Symptoms. Signs of tapeworm infection can vary slightly depending on the species of worm. Adult dogs have fewer and milder symptoms than puppies infected with tapeworms. Puppies can experience intestinal blockage, digestive upset, and stunted growth. Dogs may also experience weight loss and diarrhea. As with all intestinal parasite infections, there may be no symptoms at all.

  • Intestinal blockage
  • Digestive upset
  • Stunted growth
  • Weight loss
  • Diarrhea
  • “Bottom-scooting”
  • Visible worm segments
  • (No symptoms at all)

Segments of tapeworm bodies may be seen in infected dogs’ stools or around their anus. Because of this, owners may notice their dogs scooting their bottoms on the floor or ground. If you notice this or any other sign of tapeworms in your dog, collect a stool sample and bring it to your veterinarian for analysis.

Treatment and prevention. If your vet diagnoses your dog with tapeworms, he or she will administer oral or injectable medication as the first in a regimen of treatments to eliminate the parasites from your pet. Treatment will also include flea prevention since fleas are the most common carrier of tapeworms. This is yet another reason to protect your pet and home from fleas.


Among the smallest of the intestinal parasites are whipworms. They resemble short strands of thread, from one-quarter to one-third of an inch long. In the outdoors, whipworm eggs can survive for five years in warm, wet environments like Florida. Therefore, we should stay vigilant in our efforts to clean up after our dogs and not allow their waste to contaminate the soil.

Cause. Dogs can ingest whipworms, and their eggs, simply by sniffing or licking earth that is contaminated with them. Dogs can also acquire these parasites by eating anything that contains them, such as food, water, dirt, waste, or animal. After ingestion, whipworms take up residence in the large intestine where their eggs pass into the dog’s waste, continuing their life cycle.

Symptoms. Signs of whipworm infection can vary depending on severity, or may be absent altogether. Mild cases of infection can be symptom-free. On the other hand, whipworms can cause the colon of an infected dog to become irritated and inflamed. Signs of more severe whipworm infestation can include:

  • Weight loss
  • Mucous on a portion of stool
  • Diarrhea, sometimes bloody
  • Anemia
  • (No symptoms at all)

Treatment and prevention. A fecal exam by your veterinarian can help diagnose a whipworm infection in your dog. Since whipworm eggs within a stool sample are difficult to observe, the vet may request additional fecal exams to ensure that no false negatives are resulting from the exams. If worm eggs are present, your vet will begin a monthly treatment plan (typically three months on a dewormer) to eradicate the parasites. 

Non-Worm Parasites

Just as in the case of worm parasite infections, non-worm infections may not be accompanied by any outward signs. So be sure to follow your veterinarian’s recommendations to prevent the contracting and spread of all intestinal parasites, including the protozoal parasites described below.

Coccidia are microscopic, single-celled parasites that live in the intestines of a dog. Symptoms of coccidiosis include dehydration, abdominal upset, runny diarrhea, and vomiting. Although adult dogs are at risk of acquiring Coccidia infections, they are more common in puppies who often contract it from their mothers or siblings. Treatment includes an anti-parasitic prescribed by your veterinarian and disinfecting the home. Untreated, coccidiosis may lead to death.

Giardia, like Coccidia, are microscopic protozoa that live in the intestines. Symptoms of Giardia infection in dogs are poor coat, dehydration, loss of weight, failure to gain weight, diarrhea, and vomiting. Giardia is passed through the intestines in waste matter. Dogs can easily ingest waste-contaminated soil, puddled water, grass, and even the feces itself, which transmits the parasites in cystic form. Your veterinarian can prescribe an antibiotic like metronidazole to treat giardiasis.

Like Coccidia and GiardiaSpirochetes are non-worm parasites that invade a dog’s internal systems. All three of these parasitic conditions can infect a dog well before symptoms appear, which makes them especially concerning. Spirochetes can not only live in the intestinal tract, but also the bloodstream. As their name suggests, these are spiral-shaped bacteria. Spirochete infections can lead to Lyme disease, leptospirosis, syphilis, and other dangerous health conditions.

Please talk to your veterinarian about the threat intestinal parasites pose to your dog and other family members. Together, we can not only keep them under control but also keep them out of our life!

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Treating dogs with intestinal parasites

Northeast Animal Hospital