By The Farmer's Dog | June 8, 2023

Even in its ideal state, dog poop may not be most people’s favorite thing to see, smell, and handle. But it’s an important window into your dog’s health, and spotting worms in their stool is a sign that they need veterinary care.

Not all worms are readily visible in a dog’s stool, but some of them can be. If you notice any signs that your dog might be sick, call your veterinarian. In the meantime, here is some information about the types of worms that can infect dogs, what can happen if they do, how to recognize them, and how to prevent and treat them.

Types of worms, and how they impact dogs’ health

Dogs can be afflicted by many types of worms. They include:

Tapeworms, which find their way into dogs via infected fleas and then attach themselves to the dogs’ small intestines. While they are uncomfortable, and require treatment to prevent complications, tapeworms rarely lead to serious problems in adult dogs. They can be more dangerous for puppies, especially if an infestation gets out of control. 

Heartworms, which dogs can catch from mosquito bites. The disease caused by heartworms is very dangerous, and can cause permanent organ damage and death. Talk to your veterinarian about how to prevent heartworm disease—it’s much easier to avoid the illness than to treat it once it arises.

Roundworms, which can be passed to puppies from their mothers, and which dogs can also catch from soil, feces, and wild animals. If your dog brings you a dead rodent or bird, you may want to talk to a veterinarian about testing for the parasite. Roundworm infection is very common, especially in puppies. While not every dog who’s infected with roundworms will seem sick, roundworms can cause very serious illness and should be treated. Humans can catch roundworms from dogs and other animals, too, and can get very sick from them.

Whipworms, which dogs can catch in many of the same ways as roundworms. They won’t always cause illness, but serious infections can cause severe gastrointestinal problems and even threaten a dog’s life.

Hookworms, which puppies can catch from their mothers’ milk and all dogs can catch by coming into contact with infected feces or other contaminated items in their environments. Hookworms are dangerous to any dog, and can cause anemia and blood in the stool. They are especially hazardous to puppies, and can be fatal.

Despite its misleading name, ringworm is a fungus. Dogs can get it, though, and humans can catch it from them.

How to spot worms

If you see worms in your dog’s stool using only your naked eyes, chances are you’re looking at tapeworm segments. They often look like grains of rice on the stool. Sometimes, you may also see the worms moving in the hair near your dog’s anus or on their bed. If your dog has tapeworms, you may not see evidence every time they go to the bathroom—and your vet may not always see segments in the stool sample you submit during a routine exam.

You may also notice roundworms in a dog’s feces. They tend to be white or light brown, and can get quite long.

Even in an infected dog, you won’t usually be able to see hookworms, which are very tiny and tend to stay attached to their intestines. You’re also unlikely to see whipworms in a dog’s poop. 

All in all, if your dog shows any signs of illness, you should call your veterinarian and bring them in for an examination. Issues like diarrhea, vomiting, blood in stool, lethargy, abdominal pain, coughing, and others could be indications of various conditions, including worms, and a medical professional is best qualified to determine the cause and whether your dog requires treatment.

How a veterinarian will diagnose worms

Depending on the type of worms a vet suspects, they may use a combination of different tools to make a diagnosis. These can include blood and stool tests, X-rays, ultrasounds, or echocardiograms.

Some types of worms may require repeated testing. Whipworms, for example, only show up irregularly in a dog’s stool, so samples from an infected dog might not always provide proof that they have the parasite.

It’s important to keep up with regular veterinary visits and testing, as dogs with worms may not always seem sick. Even dogs who are on preventative medication should be tested for heartworms annually, in part because giving preventative medication to a dog who is already infected with the parasite can actually be dangerous.

How to treat worms

If your dog has worms, a veterinarian will likely prescribe medication to get rid of them. Follow their instructions, and don’t be afraid to ask questions.

After a dog has been treated for worms, it’s vital to clean their living area properly—if you don’t, they’ll be at serious risk of becoming reinfected. Consult a vet about how to safely clean and disinfect areas where worms may be hiding.

Prevention is often much easier than treatment, so talk to your vet about which parasites are common in your area and how you can go about protecting your dog from them before they have a problem.

Are worms contagious to other dogs?

Considering that feces and fleas are major ways that dogs contract these parasites, they can certainly spread from dog to dog.

Are worms contagious to people?

Humans can sometimes catch worms from dogs. People can contract and get sick from hookworms. They can also can catch roundworms through various avenues, including dog feces; roundworms can cause very serious illness in people.

Humans can’t catch heartworms from dogs, nor can other dogs—they’re transmitted via mosquito bites. While humans can contract heartworms from mosquitos, they hardly ever make people sick.

Technically, a person could catch tapeworms that their dog is carrying—but adults almost never do, because they would have to eat a flea in order to become infected. This does sometimes happen to children. The type of tapeworm that more commonly strikes humans is not the same one that dogs usually get.

While there is a type of whipworm that can infect people, it’s very rare for a person to catch whipworms from a dog—although it’s always a good idea to use common sense and follow good hygiene anytime you are handling a dog’s feces, as you never know what pathogens might be in there.

How to prevent your dog from contracting worms

How to protect your dog from worms depends on the type of worm you’re talking about. Your vet may recommend preventative medication, especially for heartworm, and some heartworm medications also guard against other types of worms.

Flea prevention will go a long way toward helping your dog avoid tapeworms. Keep their living space clean, and pay attention to any signs of itching or irritation, which could be caused by fleas.

Commonsense hygiene can help reduce the chance of spreading worms among dogs and people. Clean up your dog’s poop right away when they go to the bathroom, and always wash your hands before eating.

Other animals, or their corpses, may have fleas—so if your dog grabs hold of a mouse or a rat, that may call for testing. Also do your best to keep your dog away from stool, which can contain various types of worms.

While there are many varieties of worms that dogs can catch, and they can have serious consequences, humans have a lot of power to keep their pups safe and help them heal if they do get infected. As always, if you have any concerns, ask your veterinary care team for guidance.


This article was vetted by a vet.
Reviewed by Alex Schechter, DVM, founding veterinarian at Burrwood Veterinary.