Intestinal worms are among the most common health issues in dogs — and among the most commonly overlooked. Many dogs carry worm burdens without showing obvious symptoms, quietly shedding parasite eggs into the environment. Left untreated, worm infestations cause nutritional deficiency, organ damage, and in severe cases — particularly in puppies — can be fatal.
Regular deworming and faecal testing are cornerstones of preventive veterinary care. If your dog has not been dewormed recently or you have noticed signs that might indicate a worm infestation, contact Walker Lake Veterinary Centre at (587) 786-6771.
Some intestinal parasites of dogs are zoonotic — meaning they can infect humans. Children are particularly vulnerable. Regular deworming of dogs protects not only the dog but the entire household, making parasite control a genuine public health consideration as well as a veterinary one.
Types of Worms in Dogs
Roundworms — Toxocara canis
Roundworms are the most common intestinal parasites in dogs worldwide. Toxocara canis affects dogs of all ages but is particularly prevalent and serious in puppies.
Life Cycle and Transmission
The life cycle of Toxocara canis is complex and includes several transmission routes:
- Ingestion of infective eggs from the environment — eggs shed in faeces can survive in soil for years
- Ingestion of infected prey animals — rodents, birds, and other animals can carry infective larvae
- Transplacental transmission — larvae pass from an infected mother to her puppies through the placenta before birth
- Transmammary transmission — larvae pass from mother to puppies through milk during nursing
Transplacental and transmammary transmission are particularly significant — virtually all puppies born to infected mothers are infected with roundworms at birth or acquire them through nursing. This is why deworming protocols for puppies begin at 2 weeks of age.
Signs of Roundworm Infestation
In adult dogs with low worm burdens, roundworms may cause no obvious signs. In puppies and dogs with significant burdens:
- Pot-bellied appearance — the classic presentation in puppies
- Dull, poor-quality coat
- Failure to thrive — poor weight gain or weight loss despite adequate feeding
- Vomiting — sometimes with worms visible in the vomit
- Diarrhoea
- Coughing — during larval migration through the lungs
- Visible worms in faeces — roundworms are white to cream coloured and resemble spaghetti, typically 5 to 15cm in length
Zoonotic Risk
Toxocara canis larvae can infect humans — particularly young children who play in contaminated soil. In humans, larvae migrate through the body causing visceral larva migrans, and occasionally reach the eyes causing ocular larva migrans — potentially causing vision loss. This makes regular deworming of dogs a genuine public health priority.
Tapeworms
Two tapeworm species are commonly found in dogs in Alberta — Dipylidium caninum and Taenia species. They have different life cycles and transmission routes.
Dipylidium caninum — The Flea Tapeworm
Dipylidium caninum is the most common tapeworm in dogs. Dogs acquire this tapeworm by ingesting infected fleas during grooming. The flea serves as an intermediate host carrying the immature tapeworm larva.
This means that Dipylidium tapeworm infestation is only possible in dogs that have been exposed to fleas — treating a dog for tapeworms without addressing the underlying flea infestation leads to rapid reinfection. Year-round flea prevention is essential for managing this parasite.
Taenia Species
Acquired through ingestion of infected intermediate hosts — rabbits, rodents, sheep, or cattle. Dogs that hunt, scavenge, or are fed raw meat are at highest risk.
Signs of Tapeworm Infestation
- Proglottids — tapeworm segments — visible around the anus or in faeces. They resemble small grains of rice or sesame seeds when dry, or flat, mobile segments when fresh
- Scooting along the floor — anal irritation from proglottids
- Licking at the perianal area
- Mild weight loss in significant infestations
- Most dogs with tapeworms show surprisingly few clinical signs
Zoonotic Risk
Dipylidium caninum can infect humans — particularly young children who accidentally ingest infected fleas. Taenia solium (not common in dogs) is a more serious human pathogen but Taenia species from dogs are generally not a significant human health risk in Canada.
Hookworms — Ancylostoma and Uncinaria
Hookworms are blood-feeding parasites that attach to the intestinal wall and cause blood loss. Ancylostoma caninum is the primary hookworm species in dogs in Canada.
Transmission
- Ingestion of infective larvae from the environment
- Skin penetration — larvae burrow through the skin, often through the paws
- Transmammary transmission — from infected mother to puppies through milk
Signs of Hookworm Infestation
Hookworms are significantly more pathogenic than roundworms because of their blood-feeding behaviour.
- Anaemia — pale gums, weakness, rapid breathing — particularly serious in puppies
- Dark, tarry, or bloody diarrhoea — from intestinal blood loss
- Weight loss and poor body condition
- Protein loss — oedema (swelling) in severe cases
- Skin irritation at sites of larval penetration — typically the paws
Severe hookworm infestation can be rapidly fatal in young puppies. Any puppy showing pale gums or dark bloody diarrhoea requires emergency veterinary attention.
Zoonotic Risk
Hookworm larvae can penetrate human skin causing cutaneous larva migrans — an itchy, raised, winding track on the skin at the site of penetration. Most commonly affects people walking barefoot on contaminated ground.
Whipworms — Trichuris vulpis
Whipworms live in the large intestine (caecum and colon) and cause inflammation of the bowel wall. They are acquired through ingestion of infective eggs from the environment. Whipworm eggs are extremely environmentally resistant — they can survive in soil for years.
Signs of Whipworm Infestation
- Chronic, intermittent large bowel diarrhoea — often with mucus and occasionally blood
- Weight loss
- Mild anaemia in significant infestations
- Many dogs with light infestations show no obvious signs
Whipworm diarrhoea can closely mimic other large bowel diseases including inflammatory bowel disease and colitis. Faecal testing — including centrifugation flotation which improves detection of whipworm eggs — is important to rule out this parasite in dogs with chronic large bowel signs.
Heartworm — Dirofilaria immitis
Heartworm deserves mention as a parasite of dogs, though it is technically not an intestinal worm — it lives in the heart and pulmonary arteries rather than the gastrointestinal tract.
Heartworm is transmitted by mosquitoes and is present in some areas of Alberta, particularly in warmer years when mosquito populations are high. The risk in Edmonton is lower than in more southerly regions of North America but is not negligible, particularly for dogs that travel.
Adult heartworms living in the heart and pulmonary arteries cause coughing, exercise intolerance, respiratory distress, and in advanced cases heart failure. Treatment of established heartworm infection is complex, prolonged, and potentially dangerous — prevention with monthly or topical preventive medication is strongly preferable.
Annual heartworm testing and appropriate preventive medication during the mosquito season is recommended for all dogs in Alberta, particularly those that travel.
Giardia — A Protozoan Parasite
Giardia is technically a protozoan parasite rather than a worm, but it is commonly grouped with intestinal parasites in clinical practice. It is one of the most common intestinal parasites in dogs in Edmonton — spread through contaminated water sources including streams, puddles, and standing water in parks and trails.
Giardia causes intermittent or chronic soft to liquid stool, often greasy in appearance and with an unpleasant odour. It can be persistent and difficult to eliminate completely without appropriate treatment.
Giardia is zoonotic — it can be transmitted from dogs to humans and vice versa, though the strains affecting dogs and humans differ somewhat.
Diagnosing Worm Infestations
Faecal Flotation
The standard diagnostic test for intestinal parasites. A stool sample is mixed with a flotation solution that causes parasite eggs to rise to the surface, where they are collected on a slide and examined microscopically. Different flotation solutions and centrifugation techniques improve detection rates for different parasites.
Faecal Antigen Testing
More sensitive than standard flotation for certain parasites including Giardia and hookworms. Detects parasite antigens in faeces rather than eggs — useful for detecting low-level infections.
Faecal PCR Testing
Highly sensitive molecular testing that detects parasite DNA in faeces. The most comprehensive available test for intestinal parasites but also the most expensive. Useful for recurrent or unusual cases.
Heartworm Antigen Test
A blood test detecting heartworm antigen — performed annually as part of routine preventive care in areas with heartworm risk.
Treating Worm Infestations
Treatment depends on the parasite species identified.
Roundworms
Fenbendazole, pyrantel pamoate, and milbemycin oxime are all effective against roundworms. Multiple doses are typically required because most products kill adult worms but not larval stages — repeat treatment at 2-week intervals ensures larvae that mature after the first dose are eliminated.
Tapeworms
Praziquantel is the treatment of choice for both Dipylidium and Taenia tapeworms. A single dose is typically sufficient. Concurrent flea treatment is essential for Dipylidium to prevent reinfection.
Hookworms
Fenbendazole, pyrantel pamoate, and milbemycin are effective. Severe cases with significant anaemia may require supportive care including IV fluids and blood transfusion alongside antiparasitic treatment.
Whipworms
Fenbendazole given for 3 consecutive days is the most commonly used treatment. A repeat course at 3 weeks and 3 months after the initial treatment is recommended because of the long prepatent period of whipworms and the environmental persistence of eggs.
Giardia
Fenbendazole given for 5 consecutive days is the current treatment of choice for Giardia in dogs. Metronidazole is an alternative. Environmental decontamination — bathing the dog to remove cysts from the coat, disinfecting surfaces — is important to prevent reinfection.
[H3] Heartworm
Established heartworm infection is treated with a protocol involving doxycycline, melarsomine injections, and strict exercise restriction over several months. Prevention — monthly oral or topical antiparasitic medication — is strongly preferable to treatment.
If your dog is due for deworming or you suspect a worm infestation, book an appointment at Walker Lake Veterinary Centre. Call (587) 786-6771 or book online. Located at 5109 22 Avenue SW, Southwest Edmonton.
Preventing Worm Infestations
Regular Deworming
- Puppies should be dewormed every 2 weeks from 2 weeks of age until 12 weeks, then monthly until 6 months
- Adult dogs should be dewormed at least every 3 months — more frequently in dogs with high exposure risk
- Pregnant and nursing females should be dewormed with appropriate products safe for use in pregnancy
- Discuss the most appropriate deworming protocol for your individual dog with your veterinarian
Faecal Testing
Annual faecal testing detects parasites not covered by routine deworming — particularly Giardia and whipworms — and confirms that the deworming programme is effective.
Year-Round Flea Prevention
Eliminates the transmission route for Dipylidium tapeworm — essential for dogs at flea risk.
Heartworm Prevention
Monthly preventive medication during the mosquito season — May through October in Alberta — protects against heartworm transmission. Some products also provide broad-spectrum intestinal parasite coverage.
Environmental Hygiene
- Pick up faeces promptly from the garden and public areas — reduces environmental egg contamination
- Prevent dogs from drinking from puddles, streams, or standing water to reduce Giardia risk
- Prevent hunting and scavenging of prey animals to reduce Taenia tapeworm risk
- Wash hands thoroughly after handling dogs and before eating
- Supervise children around dogs and teach handwashing after contact
Book an Appointment at Walker Lake Veterinary Centre
Walker Lake Veterinary Centre provides faecal testing, parasite diagnosis, deworming treatment, and preventive parasite control for dogs and cats across Walker Lake, Summerside, Ellerslie, Heritage Valley, and Southwest Edmonton.
Call us at (587) 786-6771 or book online. We are located at 5109 22 Avenue SW, Edmonton.
Clinic hours:
- Monday, Tuesday & Thursday: 9:00 AM – 7:00 PM
- Wednesday & Friday: 9:00 AM – 6:00 PM
- Saturday: 9:00 AM – 3:00 PM
- Sunday: Closed
Frequently Asked Questions
How do I know if my dog has worms?
Many dogs with intestinal worms show no obvious signs. When signs are present they may include diarrhoea, weight loss, poor coat condition, a pot-bellied appearance in puppies, visible worm segments around the anus, scooting, and in severe cases anaemia and weakness. The most reliable way to detect intestinal parasites is annual faecal testing — do not rely on clinical signs alone.
Can I buy deworming medication over the counter?
Over-the-counter deworming products are available at pet stores and online but typically have a narrower spectrum of activity than veterinary prescription products. They may be appropriate for routine roundworm and tapeworm prevention in healthy adult dogs but are not suitable for all parasite species, all life stages, or all dogs. A veterinary-recommended product and protocol is the most reliable approach.
How often should I deworm my adult dog?
At minimum every 3 months for adult dogs in average risk situations. Dogs with high exposure risk — those that hunt, scavenge, attend dog parks frequently, or have regular contact with young children — may benefit from more frequent treatment. Annual faecal testing helps determine whether the current protocol is adequate.
My dog eats grass and has been scavenging — should I be worried about worms?
Scavenging — eating grass, soil, faeces, or dead animals — significantly increases worm exposure risk. A faecal test is worthwhile after known scavenging episodes, and the deworming interval may need to be shortened. Contact your veterinarian for guidance on an appropriate protocol for a dog with scavenging behaviour.
Are the worms I can see in my dog’s faeces dangerous?
Visible roundworms or tapeworm segments in faeces confirm the presence of a worm infestation that requires treatment. While the sight is unpleasant, a single episode of visible worms in an otherwise well adult dog is not an emergency. Book an appointment for faecal testing and appropriate treatment. Visible worms in a puppy alongside other symptoms — pale gums, weakness, diarrhoea — warrant same-day veterinary assessment.
