How to Tell if Your Dog Has Worms

Written by Small Door's medical experts

Parasites are not just unpleasant: they can be downright dangerous for dogs. But one big problem with parasites is that it can be hard to tell if your dog is infested. The symptoms of worms in dogs can be similar to those caused by other conditions, which means you need to know what to look for. Read on to learn more about worms in dogs, and how to treat them.

In This Article

What are worms in dogs

Worms are small parasites that are common in most dogs, especially puppies, and cause a wide array of health problems. Most of these parasites take up residence in your dog’s intestines — feeding off their blood and nutrients in the intestines.

Types of worms in dogs

There are several different types of worms commonly found in dogs:

Roundworms, hookworms, tapeworms, and whipworms are gastrointestinal parasites, which means they live in the intestinal tracts of dogs. Heartworms, on the other hand, infest the hearts and lungs of dogs and can present with different symptoms from intestinal parasites. (In this article, we will mostly be talking about intestinal parasites. However, as heartworms are a serious condition, we’ll also spend a bit of time discussing how to identify them.)

Signs & symptoms of worms in dogs

There are many signs of worms in dogs. Some are specific to certain species of worms, while other symptoms, like weight loss, anemia, malaise, and changes in appetite, are more general and can also be symptoms of many other diseases and conditions. Below is a comprehensive list of all the symptoms your dog might experience.

Symptoms of Worms in Dogs

  • Weight loss

  • Anemia

  • Diarrhea

  • Loss of appetite

  • Weakness

  • Pneumonia

  • Skin inflammation

  • Dermatitis

  • Blood in feces (fresh or tarry)

  • Inflamed rectum

  • Evidence of worms in feces or around rectum (tapeworms)

  • Evidence of worms in vomit or feces (roundworms)

  • Changes in coat condition

  • Malaise

  • Lack of growth (in puppies)

  • Loss of condition

  • Pot-bellied appearance

  • Coughing, lethargy (heartworms)

  • “Scooting”

Many puppies are born with worms, infected by their mothers transplacentally; others are infected shortly after, while nursing. This is why conscientious breeders follow a deworming schedule under the guidance of their veterinarians, and why puppy owners need to understand the signs. If your puppy is not growing, has a pot-bellied appearance, or is showing any of the other symptoms of worms in dogs, make an appointment with your veterinarian to see if worms—or something else—could be the culprit.

Worms can also affect adult dogs. Heartworms are particularly dangerous for dogs of all ages, and can be fatal if left untreated. Signs of heartworms in dogs include coughing, reduced activity, and malaise.

Intestinal worms can present with a range of symptoms, depending on the type of worm. Some worm larvae migrate through the skin (and other organs), which can cause dermatitis and skin inflammation. In large numbers, most worms can cause anemia as well as weakness, malaise, and changes in appetite and coat condition; weight loss is also common. Severe infestations can lead to other conditions, like pneumonia.

Finally, you may even see physical evidence of worms in your dog’s feces or around their rectum. Worms or worm segments may look like grains of rice or small pieces of spaghetti, but keep in mind they are not always visible.

How do dogs get worms?

Dogs can contract worms in a variety of ways, depending on the species of worm.

  • Transplacental (before puppies are born, via the placenta)

  • Transmammary (when puppies are nursing, via their mother’s milk)

  • Transdermal (through the skin)

  • Contact with infected soil

  • Contact with infected feces

  • Eating wild game

  • Fleas

  • Mosquitos

Puppies can contract parasites from their mothers, either during pregnancy or while nursing. Roundworms, for instance, can cross the placental barrier, so many puppies are born already infested. Puppies can also ingest hookworms with colostrum, the nutrient-rich milk puppies drink directly after birth.

Hookworms can be transmitted through infected soil. Transdermal infection occurs when this parasite penetrates the skin while dogs lie on infected ground. The eggs are also often ingested by dogs as they play, sniff, and groom themselves in infected areas.

Infected feces can transmit whipworms, hookworms, roundworms, and other parasites, which is why good hygiene around dog poop is crucial for both your health and your dog’s. Other forms of transmission include eating infested game (tapeworms), accidental ingestion of fleas (tapeworms), and mosquito bites (heartworm).

Diagnosing worms in dogs

While knowing the symptoms of worms may help you identify a problem, the only way to tell for sure if your dog has worms—and what kind—is to consult your veterinarian. Using microscopic imaging and diagnostic tests, your veterinarian will determine if your dog has worms or another condition. It is always helpful to bring a fresh sample of your dog’s stool to your veterinary appointment.

Once your veterinarian has figured out what type of worm your dog has, you’ll be able to treat it with the appropriate medication. In severe cases, additional steps may also be needed to stabilize your dog until the parasites have been cleared from their system.

What harm can worms do?

​​If left untreated, your dog can become seriously ill. Worms not only rob your dog of valuable nutrients but they can also damage your dog’s internal organs and even be fatal. This is why it’s important to consult your veterinarian if you suspect your dog may have an infestation.

How to treat worms in dogs

At this point, you’re probably wondering how to get rid of worms in dogs—after all, thinking about parasites infesting your dog is unsettling! But before you reach for the deworming medications, make sure you consult your veterinarian about the medication that will be most effective for your dog, as well as any necessary supportive care. Bear in mind that puppies may be infested with multiple species of worms, in which case a combination of treatments or a deworming medication that targets all types of worms may be necessary.

The drugs approved for treatment of intestinal parasites in dogs include:

  • Fenbendazole

  • Milbemycin

  • Moxidectin

  • Piperazine

  • Pyrantel

  • Oxantel

  • Praziquantel

  • Epsiprantel

  • Nitroscanate

Talk to your veterinarian about the best medication for your dog.

How often should I treat my dog for worms?

As worms are most prevalent in puppies, your puppy should be dewormed at least once each month until they’re four months old.

As adults, your dog will not typically require proactive deworming as long as they are up to date on their monthly heartworm medication – most types also protect against intestinal parasites. Deworming is only required if they’re diagnosed with an infestation.

If you have an adult dog and are concerned about worms, talk to your veterinarian about your dog’s specific circumstances to make sure they are protected.

Are worms in dogs contagious for humans or other pets?

Some worms are contagious to humans. Hookworms, tapeworms, and roundworms can all be transmitted to people, and while infestation is not always serious, they can cause problems, especially for small children and people with compromised immune systems.

Is there a cure for worms in dogs?

While worms in dogs are common, fortunately, there are a couple common ways to remove the harmful parasites from your dog’s system: oral and injectable dewormers.

​​Oral Dewormers

Your veterinarian can prescribe oral medications to treat hookworms, roundworms, whipworms, and tapeworms. Sometimes multiple doses may be required to ensure all the worms are killed, since it’s possible that larvae may have hatched after the first dose was given to your dog. Heartworm medication also takes an oral form of a chewable tablet that mimics dog treats. 

Oral dewormers typically do not cause severe side effects, but should be administered properly as your veterinarian describes because they are strong medications. Using an oral dewormer on a dog that is infected with a large number of worms can result in vomiting, loss of appetite, and diarrhea. This should subside once the worms are killed or paralyzed and passed from your dog.

Injectable Dewormer

Injectable dewormers will help remove worms from the intestinal wall by paralyzing the worms. This will then allow the dog to pass the worms inside their feces. Although injectable dewormers are a one-time treatment for worms, they can result in swelling, pain, and inflammation in the local injection spot.

Is there a vaccine for worms in dogs?

Worms are not a viral disease, which means there is no vaccine for worms in dogs. However, there are preventatives that can be given monthly to prevent and treat infections.

How to prevent worms in dogs

Luckily, worms can be prevented. Some heartworm preventatives and flea and tick preventatives include active ingredients that can help prevent common intestinal parasites. Speak to your veterinarian for advice about the best preventatives for your dog.

Good hygiene is also crucial for maintaining a worm-free environment. Picking up after your dog and preventing them from consuming or sniffing the poop of other dogs—as well as eating wild animal carcasses and droppings—will further reduce the risk of your dog contracting worms.

Summary of worms in dogs

The idea that your dog could have worms is disconcerting. However, worms are treatable, and the risk of infestations can be reduced with regular preventatives and lifestyle adjustments. If you think your dog might have worms, talk to your veterinarian about the best plan of action—and your pup should be worm-free in no time.

Related articles


Roundworms in Dogs

Roundworms are common canine parasites that can significantly impact puppy health as well as posing potential risks for humans. The most common type of roundworm in dogs is Toxocara canis, although dogs do occasionally pick up other species of roundworms. Roundworms commonly affect puppies. Being aware of the signs of a roundworm infection in dogs will help you detect a possible infection before the intestinal parasites cause lasting damage or death.


Hookworms in Dogs

Hookworms are parasites that pose particular dangers to puppies, as infections can lead to fatal complications. Knowing the signs of hookworms will help you identify a possible infection while it can still be treated.


Tapeworms in Dogs

Tapeworms in dogs are common intestinal parasites. While they usually don’t cause severe problems for healthy adult dogs, they can be dangerous for puppies. Recognizing the signs of parasites like tapeworms will help you catch potential infections before they get out of control.


Should Dogs and Cats Take Heartworm Preventatives

Heartworm disease is a serious, progressive and potentially fatal infection in pets, with few early signs of infection. For dogs, prevention is far superior to heartworm treatment – and for cats, there is no treatment for heartworm. Preventing your pet from becoming infected is better for their health, less expensive, and much less time-consuming than treating heartworm itself.

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