How to Tell If Your Dog or Cat Has Worms
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By Dr Duncan Houston
Finding something moving in your pet's stool is unsettling. Yet many dogs and cats with intestinal worms never pass anything an owner can recognise.
Changes in weight, stool and energy can be clues, but they cannot identify the parasite on their own. The safest approach combines your observations, an appropriate stool test and treatment matched to your pet.
Quick Answer
Visible worms or rice-like segments can indicate intestinal parasites, but a normal-looking stool does not rule them out. Diarrhoea, vomiting, poor growth and weight loss have several possible causes, so arrange veterinary assessment rather than guessing at a wormer. Pale gums, collapse, pronounced weakness or black tarry stool require urgent care, particularly in puppies and kittens.
Which worms affect dogs and cats?
| Parasite | Possible clues | Important distinction |
|---|---|---|
| Roundworms | Occasionally long, pale worms in vomit or stool; poor growth or a swollen-looking abdomen in young animals | Many infections are invisible at home. Puppies and kittens can acquire infection early in life. |
| Tapeworms | Small moving segments or dried rice-like pieces around the anus, on bedding or in stool | Some are linked to swallowed fleas; others to eating infected prey or tissues. |
| Hookworms | Diarrhoea, weakness, pale gums or dark stool | Blood loss can be serious, especially in young animals. Adult worms are not usually seen by owners. |
| Whipworms | Recurrent diarrhoea, sometimes with mucus or blood | These are mainly a concern in dogs; testing may need repeating. |
CAPC's hookworm guidance explains the importance of blood loss, testing and follow-up. Heartworm and lungworm are different problems that may require blood tests, other samples or different prevention. A routine intestinal wormer should not be assumed to cover them.
Giardia and coccidia are microscopic intestinal organisms, not worms. They can also cause diarrhoea, particularly in young animals, and require a different diagnostic and treatment approach.
What else could explain the signs?
Scooting often points to anal sac discomfort or irritated skin rather than worms. Weight loss can reflect poor intake, dental disease, intestinal disease or another internal illness. Diarrhoea may follow a diet change or arise from infection, inflammation or a swallowed object.
A pot-bellied puppy needs assessment rather than an assumption that worms are the only issue. Coughing is also not enough to diagnose a migrating parasite. Your vet will consider the whole pattern and the animal's age, vaccination history, travel and exposure.
How quickly should you act?
- Visible segments in an otherwise well adult: contact your vet for testing and a suitable treatment plan. Keep a photograph and a safely contained sample if requested.
- Diarrhoea, vomiting, weight loss or reduced appetite: arrange assessment promptly. Seek same-day advice for a puppy, kitten, frail animal or worsening signs.
- Pale gums, severe weakness, black tarry stool, substantial bleeding or collapse: seek emergency care now.
Young animals have less reserve. Do not wait to see a worm before taking a weak or dehydrated puppy or kitten for treatment.
When is this an emergency?
Go to an emergency vet for collapse, breathing difficulty, inability to stand, severe abdominal pain or repeated vomiting that prevents keeping water down. Pale gums and weakness may indicate anaemia or poor circulation. Worms are one possible cause, but the immediate problem needs assessment regardless of its origin.
Do not give repeated worming doses while waiting for these signs to settle. A severely ill animal may need stabilisation as well as parasite treatment.
How do vets find the cause?
A stool examination can detect parasite eggs or other stages. Depending on the suspected infection, the clinic may use centrifugal flotation, antigen testing or PCR. No single test detects every parasite at every stage, and one negative result may need follow-up.
Tapeworm segments can be shed unevenly, so a photograph or actual segment can help even if a routine stool test is negative. CAPC's tapeworm guidance describes these limitations. Blood tests may be needed if your pet is weak, losing weight or suspected to be anaemic.
What should you do now?
- Record the signs, recent weights, hunting or scavenging, travel and contact with other animals.
- Bring the exact names and dates of parasite products already used. Coverage differs between ingredients.
- Ask the clinic how to collect and store a fresh stool sample. Use a clean sealed container and wash your hands.
- Give only the prescribed or advised product at the correct species, age and weight instructions.
- Complete repeat doses and follow-up tests as directed. Persistent signs need review, not endless treatment changes.
Most uncomplicated infections can be managed effectively, but severe disease, reinfection and drug-resistant hookworms can complicate recovery. Treatment response matters as much as the first dose.
Common mistakes to avoid
- Assuming an indoor cat cannot be exposed to fleas or parasites.
- Choosing a product because the packaging says “wormer” without checking its coverage.
- Using dog products in cats or guessing a small animal's dose.
- Treating tapeworm while leaving a flea problem untreated.
- Assuming every episode of scooting or diarrhoea is caused by worms.
Prevent reinfection and protect the household
Pick up faeces promptly, clean litter trays regularly, control fleas and discourage hunting, scavenging and access to raw offal. Cover children's sandpits and wash hands after handling waste or soil. Some roundworm and hookworm species can affect people; exposure routes differ, so ask a human healthcare professional about a person's symptoms.
Giardia strains often differ between animals and humans, so it should not be presented as a routine pet-to-person worm infection. Good hygiene remains sensible.
CAPC's prevention guidance recommends regular testing and parasite protection adapted to exposure. Your vet should set a local plan for your pet's age, region, travel and lifestyle, including more frequent attention during puppyhood and kittenhood.
Frequently asked questions
Can my pet have worms if I cannot see them?
Yes. Eggs are usually microscopic and many infected animals show few obvious signs.
Are rice-like pieces always tapeworm?
They may be segments, but a photo or sample helps confirm what you found. Flea control may be part of treatment.
Can I use one wormer for all parasites?
No. Products have different coverage, and some intestinal organisms are not worms at all.
Why do signs continue after worming?
The cause may be different, reinfection may have occurred, or treatment and follow-up may need adjustment. Have your vet reassess persistent signs.
Visible worms provide a clue; their absence provides little reassurance. Testing, targeted treatment and prevention give you a clearer answer and a safer plan.
For help preparing parasite questions for your veterinary team, visit ASK A VET™. Severe weakness or bleeding needs urgent in-person care.
