Worms in dogs: diagnosis, prevention, treatment

Jun 23, 2022

Are you concerned that your dog might have worms? Intestinal worms in dogs are very common and can be treated successfully. As a pet parent, be vigilant and let your vet know if you suspect that your dog might have worms.

How do dogs get worms?

Even the most beloved dogs are routinely exposed to parasitic worms. The most common canine intestinal worms in North America include the roundworm, hookworm, whipworm and tapeworm. These parasites are highly evolved, prolific creatures, and they try to find their way into your dog when outdoors. Consider, for example, that the female roundworm (toxocara canis and toxascaris leonina) produces up to 200,000 eggs per day! The eggs of another common pest, the whipworm, can survive for up to five years in the soil in many parts of the country. These are formidable animals! How the worms are transmitted depends upon the type.

The Poop Factor

Eating worms’ eggs from wild animal poop or soil contaminated with them is the most common form of intestinal worm transmission. Except for the tapeworm, it is rare that worms are visible in the stool (poop) of infected animals; the eggs and larvae that are spread this way are usually microscopic.

Dogs may also pick up worms from infected rodents, reptiles or insects that they’ve hunted down. They may even pick up their larvae and eggs from the soles of your shoes.

Greeting and Grooming

Direct contact with worm-infected dogs – realizing that the butt sniff is a standard form of canine greeting– is also an opportunity for intestinal worm transmission. The eggs of intestinal worms stick to the hair in the anal region of dogs, so even a casual dog park sniff can transmit the eggs between canines. Just sharing bedding can transmit worms from one dog to another.

From their mother

Nearly all puppies are born with roundworms, since most canine mothers have dormant roundworm larvae in their bodies. Roundworms are passed through the placenta. Hookworms are often passed to nursing puppies through their mother’s milk.


An entirely different (non-intestinal) canine parasite is the heartworm, which is transmitted by mosquitoes. This happens when the mosquito has already picked up the parasite from another dog, coyote, or fox. It then passes the larvae to your dog when it punctures your dog’s skin in search of a blood meal. Mosquitoes transmit the heartworm, which can multiply inside your dog’s heart and cause severe lung disease, heart failure and other serious complications.

What kind of worms do dogs get? Common intestinal worms


Several varieties may be transmitted when your dog licks contaminated soil, or scratches at the dirt, then licks its paws. Hookworm larvae can also penetrate skin and migrate just beneath it. Hookworms may also be passed to nursing puppies by their mother via her milk. Sometimes hookworms can be fatal in puppies if untreated, since this relentless worm might consume enough of their blood to cause anemia. Humans can get roundworms by walking barefoot in contaminated sand and soil.


Dipylidium caninum is commonly transmitted by swallowing larva-hosting fleas during grooming. The adult worms can be over a foot long, and their segments often look like white rice in the stool or around the anal area.

Roundworm and whipworm

Both of these worms are transmitted from infested feces and soil. Roundworms may also be passed in the placenta and to nursing puppies by their mother via her milk. They can migrate through the lungs, causing damage there. Roundworms can infect humans through accidental ingestion of the eggs, so it is important to use a monthly dewormer for your dog to reduce the risk of spreading them. Whipworms can cause diarrhea if they are present in a dog’s intestines for many months.

Heartworm in dogs

This especially dangerous parasite is transmitted by the bite of a mosquito carrying the Dirofilaria immitis, or heartworm larvae. Testing and consistent prevention are essential and treatment is complex.

Note that heartworms grow to be a foot or more in length, and damage lungs and blood vessels as well as the heart. Many wild mammal species, including the ubiquitous coyote, are significant carriers of the disease. An aside to cat lovers: although domesticated cats can also host heartworms, the disease progression in cats differs from that in dogs. It is as important for cats to be on monthly heartworm preventative as it is for dogs.

Less common worms in dogs


This parasite is a fly larva (two species, Cochliomyia hominivorax, Chrysomya bezziana) or maggot that feeds on the living flesh of mammals. Screwworms can enter wounds as well as body orifices (they prefer warm, damp openings like mouth, ears and nostrils). Both varieties of screwworm have been eradicated from the U.S., but traveling overseas with your pet, as well as the importation of diseased livestock from other countries, may put your pet into contact with this burrowing pest.


This dangerous parasite, Angiostrongylus vasorum, is not passed to dogs directly from foxes, which are a common carrier, or from other dogs. The worm uses slugs and snails as its host animal, passing its larvae to your dog when it eats the infected slug or snail. Even the slime trail left by these gastropods on your dog’s outdoor bowl or toy may cause the infestation.

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Signs and symptoms of worms in dogs

Adult dogs don’t usually show signs of intestinal worms or heartworms unless they have been present for a long time. The following list contains possible symptoms of worm infestation in dogs:

  • Persistent diarrhea or vomiting
  • Excessive butt-scooting and licking at their bottom
  • Persistent coughing – especially significant in puppies, where roundworms may initially infest the lungs, then are coughed up and swallowed, allowing them to infest the intestines
  • Dull fur
  • Sudden loss of appetite
  • Rapid weight loss
  • Swollen belly
  • Mucus or blood in feces – blood may appear bright red, dark purple, or black
  • Sudden decrease in energy and activity
  • Weakness and fainting
  • Labored breathing
  • Pale gums due to blood loss and anemia

Most intestinal worms rarely appear in dog feces or vomit until after a deworming. Adult roundworms look like spaghetti. Tapeworms are the exception and are commonly seen as white rice-appearing segments in the feces.

If you notice any of these symptoms, you can call Airvet with your questions and concerns. You will most likely need to schedule a live visit with your vet and bring a fresh stool sample, so they can examine it. And because worms are so common in dogs, make it a practice to always bring along a stool sample when visiting your vet, even if no signs of parasites are present.

How are worms in dogs diagnosed?

Your vet will examine your dog’s stool sample under a microscope to check for eggs from intestinal worms. Fecal flotation, where the sample is immersed in a solution which allows worm eggs and larvae to float to the surface, is the most common test. It is not a perfect test, however, since most worms don’t produce eggs every day of a month. In other words, even if the test does not find any eggs, it is still possible that your dog may have worms.

Remember that the heartworm is not an intestinal worm and must be detected by a blood test. The American Heartworm Society warns that in the early stages of the disease, many dogs show few symptoms or no symptoms at all, although internal damage is occurring.

Therefore, preventing parasites in your dog is better than dealing with them once they are present. The earlier that your dog receives a proper diagnosis and treatment, the greater the success rate of resolving the worms. Regular, annual testing – even when your dog appears healthy – is highly recommended.

How to prevent worms in dogs

Prevent your dog from eating feces (poop)

Back to the poop-eating habit. Zoologists speculate that this behavior is a holdover from times when dogs hunted in packs as scavengers and protein was often scarce. Eating poop was a way of recycling precious protein, a skill learned in puppyhood.

Stool eating deterrents in the form of supplements are offered over the counter to help correct this problem. These deterrents make your dog’s poop less appetizing, even to a devoted canine tootsie-roll aficionado.

Think 12

On the advice of The American Heartworm Society, (1) get your dog’s blood tested every 12 months for heartworm, and (2) give your pet heartworm preventative medication 12 months a year. Annual testing is necessary, even when you give your dog heartworm medication year-round, since owners occasionally miss a dosage and dogs occasionally spit out their pills. Testing your dog’s feces for parasites 1-2 times per year is just as important.

Most monthly oral and topical heartworm preventatives also contain dewormers that prevent roundworms, hookworms and sometimes, whipworms or tapeworms. There is an injectable heartworm preventive on the market, but it doesn’t provide broad-spectrum intestinal parasite prevention. Your veterinarian knows which intestinal parasites are common in your area, and will be able to prescribe the best product for your dog.

Mosquito Management

These stinging, biting pests are everywhere and their volume depends upon the climate, weather, season, and numerous other factors. Take common sense precautions to reduce their numbers. Do not allow standing water to attract mosquitoes around your home; this includes dog dishes, wading pools, bird baths, water features in your yard. In fact, even the saucer under a flowerpot is enough water to attract mosquitoes as a watery nursery for their eggs. If you have a pond, stock it with mosquito larvae-eating fish, which are a safe alternative to harsh pesticides.

Treatment: How to get rid of worms in dogs

Your vet can recommend FDA-approved, prescription treatments for intestinal parasites. These treatments may be oral, topical, or injectable. Over-the-counter products are ineffective if they are not used at the appropriate dosage and frequency.

Broad spectrum prescription medications such as Panacur (fenbendazole) and Drontal Plus (pyrantel, praziquantel, fenbendazole) may cause mild diarrhea, vomiting and temporary loss of appetite if your dog has a heavy load of worms to be treated. This response is unpleasant, but is rarely dangerous to your pet.

Praziquantel is also available as a one-time injectable treatment for tapeworm. The injection may cause temporary inflammation, pain and swelling at the injection site.

It is important to note that treating a dog who has intestinal worms sometimes requires different or more frequent medication than just preventing them, due to the parasites’ life cycles.

Overall, be aware of your dog’s whereabouts, interactions with other animals, and what your dog gets into. Naturally inquisitive canine nature leads to adventures, and adventures may sometimes result in worms! Monitor your dog’s environment, remove feces and standing water, and keep fleas under control to keep your dog healthy. In addition, commit to monthly heartworm/intestinal parasite preventative medication. And don’t skip your dog’s annual examination by your vet including routine blood and fecal checks even if your dog shows no obvious signs of worms.

Worried your dog may have worms or need some advice managing it? Talk to Airvet now to get professional advice in minutes. If you haven’t downloaded the app – what are you waiting for?