Internal Parasites in Dogs

Picture of a cute puppy

Our canine companions are our friends and family members into one, and that’s why we want to make sure that we take as much and good care of them as possible. Many studies suggest that around 60% of dog parents across the world let their dogs sleep with them in bed at night.

But the truth is that dogs are constantly exposed to diseases, and internal parasites are a common problem that can affect them, and us, as well. Some of the parasites that we will highlight below are zoonotic, so they can be transmitted to humans, so de-worming your dog regularly is a responsibility you have both for your pet and for yourself and the rest of your family.

Let’s look at what internal parasites in dogs are more common, how they are transmitted, and what symptoms our furry friends show when they have them.

Common Internal Parasites in Dogs

Before we move on to actually describing them, we decided we’d make a list so you know which ones you can expect.

  • Hookworms
  • Roundworms
  • Tapeworms
  • Whipworms
  • Spirochetes, Coccidia, and Giardia (they are not worms, but are considered internal parasites)


Hookworms can infest dogs through a variety of ways – they can be transmitted from the mother to the puppies, they can be taken from the outside environment, and their larvae can also be swallowed by ingesting them either when the dog self-cleans or when he or she comes in contact with another infested dog.

The aspect that makes the difference between hookworms and some of the other internal parasites that we will showcase here is the fact that they attach to the intestinal lining and feed on the dog’s blood. Therefore, they can cause significant blood loss and anemia, and that may lead to serious medical issues, especially in puppies.

Hookworms can be detected by your vet when examining a feces sample under the microscope. Keeping your environment clean is what can prevent a re-infection.


Roundworms are probably some of the most common internal parasites in dogs, but also in other animals. They affect puppies more than they do adults, but that doesn’t mean that senior dogs aren’t at a risk, either. They look like strips of spaghetti and usually measure between one and three inches in length. Again, your vet can use a stool sample to detect the signs of a roundworm infestation.

Some of the clinical symptoms that you can notice in a dog that has roundworms are vomiting, diarrhea, and in more severe cases, malnourishment and coughing. Some types of roundworms can be passed on to humans.


Tapeworms can be transmitted through fleas, so if your dog is bitten by one and tries to get rid of the itchiness by licking or lightly biting that body area, he or she can accidentally swallow the flea. The ingested flea carries the tapeworm egg into your dog’s digestive system and that’s where the worm starts to develop.

What’s specific about tapeworms is that they are composed of several segments, and each of these contains eggs. Therefore, if you notice that the head of a tapeworm is sticking out of your dog’s nether region, you should never try to pull the parasite out for fear of ripping it to pieces. You could make things a lot worse for your dog if you do that.

Tapeworms can also be transmitted from one dog to the other and again, some species can be transmitted to humans. The point is that keeping your canine friend flea-free is the best protection you can offer him or her against this pesky parasite. And since no one wants to see their Fido lose weight and experience digestive issues (mostly diarrhea), talk to your vet about what you can do to get rid of fleas and minimize the risks of a tapeworm infection.


Unlike some of the other parasites we talked about, whipworms rarely cause any serious digestive issues. The only clinical symptom that you might notice in a dog that carries whipworms is a mucus that seems to cover his or her feces when you take your buddy out to tend to their business.

Whipworms are small and can be transmitted through a variety of methods, but most dogs sniff them from the contaminated ground. The major issue with them is that they are very difficult to spot under the microscope, so stool samples might be useless, unlike with other worms.

Other internal parasites

Your dog can also be affected by non-worm parasites. Although they are somewhat rarer compared to the rest, these are actually dangerous because they can infect a dog and can cause no clinical symptoms at all. Coccidiosis is a disease more common in puppies but it can also affect older cats and dogs.

Spirochetes can cause a variety of illnesses from Lyme disease to venereal diseases. Giardia is endemic throughout the United States and the rest of the world, actually, and many people have even developed a natural resistance against it.

Coccidia, Giardia, and Spirochetes can be transmitted through contaminated food and water, other dogs, and even infected soil. The truth is that in their case, internal parasite control for dogs almost always involves keeping your canine friend’s living environment as clean as possible.

General Symptoms of Internal Parasites in Dogs

As you might have noticed, the clinical signs caused by some of the parasites we showcased here can be different. However, there are some that are considered common and that can be shown by most infections with any species of parasites.

With almost all worms, you’ll either see an adult or the eggs on your dog’s fur, stool, or bedding. Scooting is extremely common in dogs that have begun to release worms or larvae in their stools. Puppies that have parasites will usually show a bloated belly.

Finally, in a dog that has had parasites for a while, general clinical signs such as an increase in their appetite, weight loss, and weakness, as well as a dull coat, can tell you that something’s wrong. Typically, if a dog keeps eating and never seems to want to stop and still loses weight should definitely tell you that you need to take him or her to the vet.



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