Worms in Dogs: Symptoms, Treatment, and Prevention Tips

Learning that your dog may have worms is enough to make any pet parent shudder, but intestinal parasites are far more common than many people realize. Dogs of all ages can become infected, whether they’re sniffing around the backyard, playing at the dog park, or even nursing tiny puppies.

While mild cases of worms might not cause issues immediately, worms can quickly multiply, leading to uncomfortable symptoms and serious health problems if not addressed. The good news is that worms in dogs are usually detectable and treatable with the right veterinary care.

What Exactly Are Worms in Dogs?

Worms are internal parasites that live inside your dog’s digestive system or, in some cases, in vital organs like the heart and lungs. They survive by feeding on nutrients or blood, which can lead to malnutrition, weakness, and life-threatening complications when infestations grow severe.

Dogs can contract worms in a variety of ways: by ingesting worm eggs from contaminated soil or feces, eating infected prey animals, swallowing fleas during grooming, or even before birth through their mother. Because many worms are microscopic at first and not visible in your dog’s stool, pet parents often have no idea their dog is infected until symptoms appear.

Signs and Symptoms of Worms in Dogs

Each type of parasite affects the body differently, but most worm infections lead to some degree of digestive upset. Dogs may experience diarrhea, vomiting, weight loss, or a swollen abdomen, particularly in puppies. A dull or poorly maintained coat is often an early clue that something is wrong internally, as the parasites interfere with your dog’s ability to absorb nutrients.

Some dogs scoot or excessively lick the anal area due to irritation around the rectum. In more advanced cases, worms may become visible in a dog’s vomit or feces, though this is not always the case.

There are Five Different Types of Worms That Your Dog Might Contract:

1. Heartworms: The Most Dangerous Parasite

Among all the types of worms dogs can get, heartworms are considered the most serious and life-threatening. Transmitted through mosquito bites, these parasites take up residence in the heart, lungs, and surrounding blood vessels. Because mosquito exposure is nearly impossible to avoid, heartworms pose a risk to dogs throughout the country. Early symptoms are often subtle and may simply look like reduced stamina or a lingering cough.

As the disease progresses, dogs may struggle to breathe, lose weight, or develop pale gums due to decreased blood flow. Untreated heartworm disease can lead to organ failure and death.  Prevention is the best way to avoid heartworms, and once adult heartworms are discovered, your dog’s treatment can become lengthy, expensive, and physically demanding for your dog.

2. Roundworms: Common in Puppies and a Risk to Humans

Roundworms are among the most frequently diagnosed internal parasites in dogs, especially in puppies. Many puppies are actually born with roundworms or acquire them through their mother’s milk shortly after birth. These worms can cause a pot-bellied appearance, stunted growth, digestive problems, and general discomfort.

Roundworms are also a zoonotic parasite, meaning they can be passed to humans, typically when microscopic eggs contaminate hands or surfaces. This makes regular deworming, and stool checks especially important in homes with young children. Fortunately, roundworm infections are usually easy to diagnose through a fecal test and can be treated with medication.

3. Tapeworms: Often Linked to Fleas

Tapeworm infections occur when a dog ingests an infected flea or, more rarely, a rodent or other prey animal carrying the parasite. Tapeworm segments may appear near a dog’s rear end or in their stool, resembling tiny grains of white rice. While tapeworms don’t always cause obvious illness, they can contribute to weight loss and irritation under the tail area. Because fleas are the most common source, treating both the tapeworm infection and the flea population is essential to prevent the cycle from repeating.

4. Hookworms: A Serious Threat to Young Puppies

Hookworms are intestinal parasites that cause anemia in dogs and can be fatal in puppies, if left untreated. There are several different kinds of hookworms that can affect dogs, but all feed on your dog’s blood. Your dog can get hookworms from ingesting hookworm larvae from the environment, or the infected larvae can pass from a mother’s milk to her puppies. Hookworms are diagnosed by fecal floats and are treated with deworming medications.

5. Whipworms: Persistent and Often Hard to Detect

Whipworms are a type of worm in dogs that live in the large intestine and colon, where they pass their eggs into the dog's feces. The eggs can survive for up to five years in suitable environments (warm and moist), which is one of the reasons why cleaning up after your dog immediately is so important for general sanitation and health.

Whipworms don’t necessarily cause symptoms in mild cases, but in severe cases they can lead to inflammation, weight loss, diarrhea, and occasionally anemia. Your veterinarian can diagnose your dog for whipworms with a fecal sample and will prescribe a treatment plan suitable to your dog’s needs.

Diagnosing and Treating Worms in Dogs

Annual fecal testing is one of the most effective ways to detect intestinal parasites early. Many worms are impossible to see with the naked eye, so relying on visual inspection of stool alone is not enough. In the case of heartworms, a simple annual blood test is used to identify infections before serious organ damage occurs.

Treatment for worms varies depending on the parasite, but most intestinal worms respond well to prescription medication. Over-the-counter dewormers can be unreliable or only target certain types of worms, which is why you should see your veterinarian for a proper diagnosis and treatment.

Preventing Worms: Your Dog’s Best Defense

Preventing worms in dogs is much easier than treating the illnesses they cause. Consistent parasite prevention medication can protect your dog from heartworms and many intestinal worms at the same time. Keeping your dog on a year-round prevention schedule is one of the most effective ways to keep worms from becoming a problem.

Good hygiene also plays a major role in preventing worms. Cleaning up your dog’s feces promptly, making sure they don’t eat their poop and protecting your dog from fleas, as well as routine wellness exams with your veterinarian can help reduce the risk of infection. Puppies require a more frequent deworming schedule during their early development, and your veterinarian will guide you on the appropriate timing.