Do You Know the Symptoms of Worms in Dogs?

If your dog has worms, you may be fortunate to see actual evidence of these pesky critters, but the symptoms of worms in dogs are often subtle or nonexistent altogether.

Roundworms, hookworms, whipworms and tapeworms are some of the most common intestinal parasites in dogs. If your dog only has a worm or two, then there may not be any signs, other than eggs that show up in a fecal exam.

In contrast, even a few heartworms are a big concern because they live in a dog’s heart and lungs, not in the intestinal tract. Imagine the damage worms that can grow to be a foot long can do to a dog’s cardiovascular system.

Let’s look at the common symptoms of worms in dogs and what you can do to protect your canine companion.

Roundworm Symptoms in Dogs

Roundworms are especially common in puppies (symptoms of roundworms in dogs who are older are rare) and the younger a dog is, the more likely they are to develop symptoms of puppy worms like:

• Pot-bellied appearance
• Poor growth
• Weight loss
• Vomiting
• Diarrhea
• Rough coat
• Pale gums
• Loss of appetite
• Low energy/lethargy
• Visible worms in dog vomit or poop (they look like spaghetti) particularly after deworming
• Coughing due to the migration of larvae (an immature form of the parasite) through the lungs

Hookworm Symptoms in Dogs

Both adult dogs and puppies can develop signs of worms when they have hookworms, but puppies are at highest risk for becoming extremely sick and even dying. Hookworms attach to the wall of a dog’s intestine and feed on blood. They can leave tiny, bleeding ulcers behind when they detach. Symptoms of hookworms in dogs include:

• Pale gums and low energy due to anemia (a low red blood cell count)
• Poor growth
• Weight loss
• Poor appetite
• Diarrhea
• Blood in a dog’s stool (digested blood is black and tarry)
• Coughing due to the migration of larvae (an immature form of the parasite) through the lungs

Whipworm Symptoms in Dogs

Whipworms are usually diagnosed in adult dogs rather than in puppies. Dogs with light worm burdens typically have no signs of worms at all. However, dogs who have lots of worms in their intestines can develop:

• Diarrhea that may contain blood or mucus
• Weight loss
• Dehydration
• Pale gums and low energy due to anemia (a low red blood cell count)

Tapeworm Symptoms in Dogs

The symptoms of tapeworms in dogs are a bit different than the signs of roundworms, hookworms or whipworms. Dogs rarely get sick from tapeworms, but you might notice:

• Tapeworm egg packets called proglottids wherever your dog sleeps or stuck to their fur near their anus. Newly emerged proglottids are white, flat and may wiggle, while dried proglottids look like big grains of rice. These can also be seen in the stool.
• Scooting — a dog dragging their bottom across the floor
• A lot of licking around the anus
• If heavily infested with tapeworms, a dog might also lose weight despite eating its normal food amount.

Heartworm Symptoms in Dogs

Adult heartworms live in a dog’s heart and lungs. Infected dogs may look healthy early in the course of the disease, but they develop symptoms like:

• Coughing
• Difficulty breathing
• Tiring quickly
• Not wanting to exercise
• Weight loss
• Pot-bellied appearance due to heart failure and fluid collecting within the abdomen

Dogs get roundworms, hookworms, whipworms, tapeworms and heartworms in different ways:

Roundworms – Infected dogs shed roundworm eggs in their feces. Dogs then eat those eggs (by licking contaminated soil off their fur, for example) or eat a prey animal that ate the eggs. Puppies can also get roundworms from their mother while developing in her uterus or by suckling her milk.

Hookworms — Infected dogs shed hookworm eggs in their feces. The eggs hatch into larvae that can be eaten or that burrow through a dog’s skin. Dogs can also eat other animals that are infected with the larvae, and puppies may get hookworms through their mother’s milk.

Tapeworms — Tapeworm proglottids wiggle their way out of an infected dog’s anus, dry out in the environment, and release the eggs they contain. With the most common type of dog tapeworm, fleas eat the eggs, and dogs eat the infected fleas when they groom themselves.

Whipworms — Infected dogs shed whipworm eggs in their stool. These eggs can survive for years in the soil, and dogs can inadvertently eat them as they go about their normal activities.

Heartworms — Dogs get heartworms when they are bitten by a mosquito that previously bit an infected dog and picked up microscopic heartworm larvae.

If you find that your dog has intestinal worms, there are steps you can take to remove them from your pet’s system. Over-the-counter products are available but choose wisely — some are safer and more effective than others. (Chewy offers a range of safe products for worms in dogs.) A good, broad-spectrum option is Bayer Quad Dewormer, which kills roundworms, hookworms, whipworms and tapeworms. Make sure you closely follow the directions printed on the label of any deworming medications you give your dog.

However, it’s unlikely that your dog has roundworms, hookworms, whipworms and tapeworms at the same time. If you’d rather take a more targeted approach, bring a fresh fecal sample to your veterinarian’s office. They can look at it under the microscope to determine what type of worm your dog has and then prescribe the deworming medications that will work best. Tapeworm and whipworm eggs can be hard to find in a fecal sample, so make sure you also tell your vet what symptoms you are seeing at home.

Treatment for canine heartworm disease is a serious matter and varies based on how sick a dog is. First, your vet will run appropriate tests to determine if your dog has heartworms and if so, how much damage they’ve done. Many dogs will then receive three injections of a drug that kills adult worms over the course of a month or so as well as medications to kill immature worms and anything else needed to stabilize their condition. It’s absolutely vital that dogs rest as the heartworms die and are absorbed by the body. Other treatment protocols may be appropriate based on the specifics of a dog’s case.

Preventing worms is a much better option than treating them once they’ve taken up residence in your dog. Not only can worms make your dog sick, but some types are also harmful to people. For example, children can accidentally eat roundworm eggs, and when the larvae hatch, they can end up in their eyes. Hookworm larvae can burrow through your skin and cause an itchy rash.

The best way to prevent worms and to keep pets and people safe is for dogs to receive heartworm prevention year-round. Most of these medications contain additional ingredients that will kill many of the intestinal worms that your pet might encounter.

Keep your dog current on all their parasite prevention and check with your veterinarian to make sure that the heartworm prevention you give protects against intestinal worms too. However, no medication is 100% effective, so it’s still important to get fecal exams and heartworm tests on a regular basis. Your veterinarian can recommend an appropriate testing interval based on your dog’s age, lifestyle, and the type of parasite prevention they’re on.

Frequently Asked Questions

Q: Are worms in dogs contagious?

A: Worms in dogs are contagious, but not in the way you might think. Dogs don’t often directly infect other dogs with worms — except when mothers pass roundworms and hookworms on to their pups. Instead, dogs shed intestinal worm eggs in their feces, and those eggs are responsible for infecting new dogs, often through another host like a flea or rodent. Heartworms are transmitted between dogs through the bites of infected mosquitos. Humans can become infected with roundworms, hookworms and tapeworms by interaction with infected animal feces or surfaces an infected pet has touched.

Q: Can worms cause aggression in dogs?

A: Worms don’t normally cause aggression in dogs, but any dog who is sick may act more aggressively than normal if they feel vulnerable and are worried that they may need to protect themselves.

Q: Do worms in dogs cause diarrhea?

A: Many types of worms in dogs cause diarrhea. Roundworms, hookworms, whipworms and other intestinal parasites may all be to blame. A veterinarian can look at a fecal sample under the microscope and determine if worms are a likely cause of the diarrhea. Puppy worm symptoms tend to be worse than what adult dogs experience. 

Q: What causes worms in a dog's poop?

A: Worms in a dog’s poop may be visible under certain circumstances. Tapeworm segments, which can be white, flat, and wiggly or look like big grains of rice, can show up in a dog’s poop. You might also see roundworms (they look like spaghetti) if a dog has lots of worms or after they’ve been given a deworming medication. Dog worms in vomit are usually roundworms. While it is possible to observe visible proglottids from tapeworms that can be seen in stool, typically signs of worms in dog poop or vomit are rare with other types of intestinal parasites.

There are no “stupid” questions when it comes to your pet’s health. If you suspect your pet is sick, please call your vet immediately. For health-related questions, always consult your regular veterinarian when possible as they can make the best recommendations for your pet. (If you need help finding a vet near you use this link.)

Additional expert input provided by Dr. Jennifer Coates, DVM.