Types of Worms in Dogs: Signs, Diagnosis, Treatment & Prevention

At a glance

• Dogs can pick up several different internal parasites (roundworms, hookworms, whipworms, tapeworms, heartworms).
  
• Transmission varies: from moms to puppies, from insects (fleas, mosquitoes), from prey, or from contaminated soil.
  
• Vets diagnose worms with fecal tests and (for heartworm) blood tests.
  

Monthly preventatives and good hygiene dramatically reduce risk.

Disclaimer: This article is educational and not a substitute for veterinary care. If you suspect worms, contact your veterinarian.

What do people mean by “worms” in dogs?

“Worms” is a catch-all term for internal parasites that live in a host (like your dog) and rely on that host for survival. Most live in the intestines; heartworms live in blood vessels of the heart and lungs. Even mild infections can sap nutrients; severe infections can cause significant illness.

How do dogs get worms?

Different parasites have different life cycles, but common routes include:

• Mother to puppy: Before birth or through nursing.
  
• Insects: Mosquitoes (heartworm) and fleas (some tapeworms).
  
• Prey/wildlife: Eating infected rodents, rabbits, or other animals, or scavenging.
  
• Environment: Ingesting or contacting eggs/larvae in soil, grass, or contaminated surfaces.
  

Good news: understanding these routes makes prevention very doable.

The most common types of worms in dogs

Roundworms

How infection happens: Puppies are frequently exposed from their mothers; dogs can also ingest eggs from soil or eat infected small mammals.

Typical signs: Many dogs appear normal. Possible signs include a pot-bellied look (especially in pups), poor weight gain, vomiting or diarrhea; sometimes spaghetti-like worms are seen in vomit or stool.

Human risk: Roundworms are zoonotic, people can accidentally ingest microscopic eggs from contaminated environments. Handwashing and prompt poop pickup matter.

Hookworms

How infection happens: Ingesting larvae from the environment, nursing from an infected mother, eating infected insects/prey, or larvae penetrating skin (e.g., walking on contaminated ground).

Typical signs: Vomiting, diarrhea, weight loss, anemia, or blood in stool. Migrating larvae can occasionally cause coughing or itchy skin.

Why they’re serious: Hookworms attach to the intestinal lining and can cause significant bleeding. They’re also a zoonotic concern through skin contact with contaminated soil.

Whipworms

How infection happens: Dogs ingest eggs directly from contaminated environments, no intermediate host.

Where they live: Large intestine/colon.

Typical signs: Chronic or intermittent diarrhea, weight loss, straining to defecate, and sometimes anemia. Eggs persist in moist environments, so sanitation is key.

Tapeworms

How infection happens:

Dipylidium caninum is spread by fleas, dogs swallow infected fleas while scratching/chewing.

Taenia species come from eating infected prey or raw offal.

Typical signs: Often none. Owners may notice “rice-like” segments around the anus or in stool, plus occasional scooting or mild digestive upset.

Prevention angle: Controlling fleas interrupts the most common tapeworm cycle.

Heartworms

How infection happens: Mosquitoes transmit heartworm larvae, which migrate to vessels of the heart and lungs.

Typical signs: Early infections are silent. As worm burden grows: cough, exercise intolerance, difficulty breathing, collapse, and potentially death.

Who’s at risk: Heartworm disease has been reported in all 50 U.S. states. Year-round prevention is strongly recommended.

How can you tell if your dog has worms?

You may not, many infections are subclinical. When signs do occur, they often include:

Intestinal worms: Diarrhea, vomiting, gas/bloating, weight loss, poor coat, pot-bellied appearance (pups), visible worms or segments in stool/vomit.

Heartworms: Usually no early signs; later, coughing, reduced stamina, breathing trouble, fainting/collapse.

Any of these signs warrant a conversation with your vet.

How vets diagnose worms

Physical exam: May reveal bloating, poor body condition, tapeworm segments, or abnormal heart/lung sounds.

Fecal testing: A fresh stool sample is examined (often via flotation) for parasite eggs/larvae. Because shedding can be intermittent, a single negative test doesn’t always rule out parasites, your vet may recommend repeat testing.

Blood testing (heartworm): A rapid in-clinic antigen test screens for heartworm. Positive screens are confirmed with additional tests before treatment planning.

Treatment options

Intestinal worms

Dewormers: Your vet will select medications that target the identified parasite(s). Many are given by mouth; some are topical.

Sanitation: Thorough poop pickup indoors and out, laundering bedding, and disinfecting hard surfaces help prevent re-infection and protect other pets and people.

Hygiene tips: Wipe your dog’s hindquarters and paws after outdoor time during treatment, especially in multi-pet households or yards used by many dogs.

Heartworms

Why it’s different: Heartworms live in critical blood vessels; killing them must be done carefully to avoid complications.

Typical plan: Staged therapy over months using a combination of oral meds and injections following current guidelines, plus strict exercise restriction during treatment to reduce the risk of emboli and inflammation. Your vet will tailor the protocol to disease stage.

When to call your vet

You see worms or “rice-like” segments on your dog or in stool/vomit.

Your dog shows gastrointestinal signs that persist beyond a day or two.

You notice coughing, reduced exercise tolerance, or any breathing changes.

Your dog was exposed to a dog with known parasites or had a lapse in preventatives.

It’s time for the annual fecal exam and heartworm test (or as recommended locally).

Preventing worms in dogs

Use monthly preventatives: Many products combine protection against heartworm plus fleas/ticks; some also include intestinal dewormers. Your vet can recommend a year-round plan for your region and your dog’s lifestyle.

Control fleas and mosquitoes: This reduces risk for tapeworms (Dipylidium) and heartworms.

Prompt poop pickup: At home, on walks, and in shared yards.

Limit risky snacking: Discourage eating wildlife, carcasses, or unknown materials outdoors.

Routine screening: Annual fecal checks (more often for high-risk dogs or kennels) and yearly heartworm testing, even if on preventatives.

FAQs

Can people catch worms from dogs?

Some can, particularly roundworms and hookworms, via contaminated environments. Pick up poop promptly, wash hands, and keep dogs on preventatives.

How often should puppies be dewormed?

Puppies are commonly dewormed on a schedule starting in early life (because exposure from mom is common) and tested regularly. Your vet will set the cadence.

Do indoor dogs need prevention?

Yes. Mosquitoes and fleas get indoors, and many intestinal parasites come from tracked-in soil or contact with other pets.

Can I just buy an over-the-counter dewormer?

Self-treating can miss the real culprit or underdose your dog. Proper testing and a vet-directed product/dose are the safest, most effective route.

 

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Bottom line

Worms are common, often silent, and very preventable. Partner with your vet for routine screening, year-round preventatives, and smart hygiene to keep your dog, and household, safe.