types of dog worms

6 Types of Dog Worms: Common Internal Parasites of Dogs

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All dogs suffer from worms and other internal parasites during various portions of their lives. These invaders are most commonly a problem for puppies, but they occasionally infect adult dogs too.

Therefore, it is important for dog owners to familiarize themselves with the most common types of dog worms (and other parasites) that can infect dogs.

We’ll try to help you do so below, as we explain the six most important worms that infect dogs, the symptoms that may indicate a parasite problem, and the basic treatment strategies you can employ. We’ll also discuss the threat these dog worms can pose to you and your family, and the steps you’ll want to take to keep yourself safe.

Are Worms and Parasites Dangerous for Dogs?

Simply put: Yes. Some worms and other parasites can be very dangerous for dogs.

Most worms in dogs will cause minor health problems, but they’re generally not “dangerous” in small numbers. However, even the most common parasites can become dangerous if their populations are allowed to grow out of control.

Other worms and parasites can be quite dangerous, even in small numbers. A single heartworm or tapeworm, for example, could conceivably lead to a dog’s death (although such extreme outcomes are quite rare).

A few of the most serious health risks worms and other parasites present include:

  • Some worms can migrate from areas in which they won’t cause serious problems, to areas in which they can cause extraordinary damage. For example, some worms may tunnel outside the digestive tract and end up inside the liver, heart or brain.
  • Some worms can steal so many resources from a dog that they can trigger malnutrition and eventual starvation. Parasites that feed on a dog’s blood may end up causing a dog to become anemic.
  • Some parasites release toxins that can trigger life-threatening septicemia (blood poisoning).

treating dog worms

General Symptoms of Worms and Parasites in Dogs

Different worms affect dogs in different ways. In fact, individual dogs will often suffer from different reactions to the same parasite. We’ll talk about some of the specific symptoms caused by different types of parasites later, but some of the most common symptoms that can indicate a worm or parasite infection include:

  • Diarrhea
  • Constipation
  • Vomiting
  • Excessive hunger
  • Loss of appetite
  • Reduced energy level
  • Depression
  • Unexplained weight loss
  • Poor coat condition
  • Pot-bellied appearance
  • Belly pain

How Do Dogs Get Worms?

Different worms and parasites infect dogs in different ways. We’ll discuss the specific route by which different types of worms infect dogs below, but there are three basic methods of transmission:

Fecal-Oral Route

The majority of worms and other parasites that infect dogs are transmitted via the fecal-oral route. This occurs when a dog inadvertently ingests eggs or larvae that’s been passed in the feces of other animals. Dogs can also re-infect themselves in this manner, which can lead to very significant infestations.


Heartworms are spread through the bites of infected mosquitoes. And while not every mosquito is infected with heartworms, all it takes is a single bite from an infected individual to cause your dog to suffer from heartworm disease.

Flea Ingestion

Most dogs who contract tapeworms catch them when they accidentally consume fleas. Dogs can also contract tapeworms by eating contaminated meat, but this isn’t very common in the modern world.

worms that infect dogs

How Can You Determine If Your Dog Has Worms?

Many of the symptoms listed above can be caused by a wide variety of health problems. This makes it important to verify that your dog actually has worms, so you can take steps to eliminate them (or treat whatever the problem actually is).

The best way to determine if your dog has worms is to visit your veterinarian. Your vet will likely ask you several questions about your pet’s health and perform a physical examination.

Then, he or she will likely take a stool sample or perform an anal swab. The sample will then be viewed microscopically to determine if any worms (or, more commonly, worm eggs) are present. In some cases, other types of samples, including blood or saliva, may be collected for analysis too.

You can also use a mail-order worm testing kit, like the Perfect Pet Products Fecal Worm Test, to determine if your dog has worms. The kit will require you to obtain a stool sample, place the sample inside a special pouch, and then mail it to a lab for analysis. You’ll usually obtain the results within 24 hours.

Note that dogs and puppies occasionally expel live worms (or pieces thereof) when they vomit, cough or defecate. And while this is obviously indicative of an infestation, it doesn’t necessarily tell the whole story. After all, dogs and puppies often suffer from several different parasite infestations at the same time.

General Strategies for Treating Worms and Parasites in Dogs

Most worms can be treated with simple and safe medications. Some of these medications are available over-the-counter, but others will require a prescription from your vet. Most of the common medications used to treat worms are effective on more than one species, which helps to simplify the treatment in many cases.

It is also important to keep your dog’s environment exceptionally clean during and after the treatment process. Many of the most common internal parasites and worms that infect dogs are spread via the fecal-oral route. This means that the eggs or larvae are expelled in a dog’s feces, and they infect other dogs when they’re inadvertently ingested.

So, it is important to keep your dog, his bed, and your backyard clean while battling a worm infestation.

Can people get dog worms

The 6 Most Common Types of Dog Worms and Parasites in Dogs

There are a variety of different worms and parasites that can infect your dog, but some are much more common than others. The six most common types are listed below.

1. Heartworms

Heartworms are roundworms that can cause a very serious illness called heartworm disease.

Heartworms are unlike many of the other worms that commonly afflict dogs, as they’re spread via mosquitos. The heartworm larvae enter your dog’s bloodstream during the mosquito’s feeding activity, before spending the next five to seven months maturing. At this point, they migrate to your dog’s heart and begin reproducing.

Heartworms can grow to about a foot in length, and your dog may end up with more than 100 of them living inside his heart. This can reduce the pumping efficiency of your dog’s heart, and lead to congestive heart failure. Left untreated, heartworm disease is often fatal.

There are treatments available for heartworm disease, and they’re often effective. However, treatment is very expensive, and you’ll need to limit your dog’s activity for several months while the medications are killing the worms. If you don’t, small pieces of the dying worms may break off and cause deadly blockages of the pulmonary artery.

Fortunately, heartworm disease is very easy to prevent with a simple oral tablet, given about once per month. You’ll need to obtain the medication from your vet, but it is generally pretty affordable.

2. Tapeworms

Tapeworms are flatworms which infect a wide variety of animals, including wild and domestic species. They typically use tiny hooks near their mouths to latch on to the intestinal walls of their hosts, where they grow and feed. Many species are famous for reaching several feet in length, although such gigantic tapeworms are pretty rare.

A few different species of tapeworms can infect dogs, but Dipylidium caninum, often called the flea tapeworm, is probably the one that most commonly plagues dogs. This tapeworm spends part of its lifecycle living in the bodies of fleas. When dogs bite or lick fleas, they can contract the worms (which illustrates the importance of flea prevention).

Nevertheless, most tapeworms respond to similar medications, so it isn’t important to determine the exact species infecting your dog before starting treatment. Most owners discover that their dog is infected with a tapeworm by noting small pieces of the worm (which are shed as part of the reproductive process) in their dog’s feces.

It is generally pretty easy to eliminate tapeworms from your dog’s digestive tract with a few rounds of anti-worming medications. Although people can get tapeworms, they have a complex lifecycle that requires an intermediate host. This means you cannot get them from your dog.

3. Roundworms

Roundworms are some of the most common parasites to infect dogs. These worms are typically about 2 to 5 inches long, and they have a round cross-section. They can be various shades of brown, yellow or white, and you may see them expelled with your dog’s vomit, feces or sputum. They’re often described as having a spaghetti-like appearance.

Most adult dogs probably have a few roundworms in their bodies, but their immune systems are usually robust enough to keep the worm populations in check. This means that low-level roundworm infestations don’t cause many problems for adult dogs. Puppies, on the other hand, are quite susceptible to these parasites, which they can contract directly from their mother, or from the environment.

Roundworm infestations are so common in puppies that most vets will prescribe worming medications for puppies as a matter of practice – samples are rarely taken to confirm the infestation. Puppies are usually treated for roundworms (and several other parasites) at 2, 4, 6, 8 and 12 weeks of age.

Roundworms can make puppies pretty sick, and eventually cause malnutrition, so it is important to take them seriously. Additionally, you can catch roundworms from your pet. In some cases, these roundworms can cause serious illness in humans.

4. Hookworms

Hookworms are named for the hook-like structures located near their mouths, which the worms use to attach to the lining of your dog’s intestines. They can infect dogs of any age, but they are generally a much bigger concern for puppies than adults. Hookworms can cause serious illness in dogs, and they can even cause some dogs to die rather suddenly.

Hookworms can be contracted in a variety of ways. Puppies can ingest them while nursing, and they can also be contracted from the environment. Most are probably ingested inadvertently, but hookworms have been known to infect dogs (and people) by simply tunneling through the skin.

Hookworms are microscopic, so you won’t see them in your dog’s feces. Instead, you’ll just need to stick to an appropriate worming schedule and watch your dog closely for signs and symptoms that may indicate an infection.

Some of the most common symptoms of hookworm infestations include diarrhea, constipation and a loss of appetite. Additionally, because hookworms may migrate up to the upper portions of the digestive tract, they can occasionally find their way into the lungs or trachea, where they’ll cause puppies to cough.

Note that hookworms can be transmitted to people, so prompt treatment and proper hygiene are critical when dealing with an infected dog.

5. Whipworms

Whipworms are long, thin worms that look like tiny hairs or threads. They usually have an enlarged head, which is thicker than their whip-like tails. Whipworms can be seen in a dog’s feces, but they aren’t observed as often as roundworms or tapeworm segments are.

Whipworm infestations can be difficult to diagnose, as the worms are very small, and they don’t pass many eggs in a dog’s stool. Accordingly, vets will often administer medications to eliminate whipworms whenever dogs exhibit symptoms that suggest an infection.

The two most common symptoms whipworms cause include long-term weight loss and the mucous-covered stools. Whipworms rarely cause deaths in dogs, but they can be very troubling and make your pet feel pretty miserable. Humans can get whipworms, but the species that infects dogs is rarely transmitted to people.

Whipworms can infect dogs of any age, but they’re most commonly a problem for puppies. Fortunately, while they’re hard to diagnose, they’re generally rather easy to eliminate with an appropriate worming medication.

6. Protozoans

While they aren’t worms, protozoans are microscopic, single-celled organisms that can also infect dogs. There are a variety of protozoan species that can afflict dogs, but those belonging to the genera Giardia, Isospora and Entamoeba are the most common.

Different protozoans cause different signs and symptoms, although most trigger diarrhea. Sometimes, the diarrhea can be bloody or extremely frequent, and this can lead to dehydration and weight loss. However, some dogs remain infected with protozoans without displaying any symptoms of illness.

As with most other parasites, protozoans are more troubling for puppies than adult dogs. Dogs typically get them from inadvertently consuming contaminated soil, food or water. Some protozoans are easier to diagnose and treat than others, and strict hygiene is important during treatment to prevent your dog from becoming re-infected.

Several protozoans can be spread to humans, so it is important to wash your hands frequently when treating dogs who are infected with protozoans. It is occasionally necessary to quarantine infected dogs to prevent them from spreading the parasites to other pets in the home.

What kind of worms do dogs get

Dog Worms at a Glance

There are a lot of different worms that infect dogs, and it can be difficult for some owners to remember which worms cause which symptoms, and which ones are likely to cause the most significant problems. We’ve made the following chart to try to help with this problem.

ParasitePrimary SymptomsVisible in Stools, Vomit or Sputum?Potentially Fatal?A Threat to Humans?
HeartwormsNone initially. Eventually, most dogs will become lethargic and tire easily.No.Yes. Heartworms are very dangerous for dogs.No.
TapewormsTypically, tapeworms don’t cause symptoms, although dogs may eventually begin losing weight.Small, rice-like segments are often visible.UnlikelyNo.
RoundwormsPot-bellied appearance, diarrhea, weight loss, loss of appetite.Spaghetti-like worms often expelled in feces, vomit or sputum.Possible, but unlikely.Unlikely.
HookwormsDiarrhea, constipation, lack of appetite and coughingNo.Yes. Hookworm infestations can be deadly.Yes.
WhipwormsWeight loss and mucous-covered stools.Rarely. They appear like small hairs that are large at one end.Possible, but unlikely.No.
ProtozoansDiarrhea, which may occasionally be bloody or extremely frequent.No.Yes. Protozoans can cause death if left untreated.Yes.

Dog Worm FAQs

Owners often have questions regarding dog worms and other parasites, so we’ll answer some of the most common questions below.

What are the small, white things in my dog’s poop?

You are probably looking at portions of a tapeworm that are shed as part of the worm’s reproductive process. They are often likened to grains of rice, and they can be brown, yellow or white.

What does it mean if there are worms in your dog’s poop?

If you see worms in your dog’s feces, it usually means your dog is suffering from a roundworm infestation. Roundworms are several inches long and they typically look like spaghetti. You may also see whipworms in your dog’s poop, but these typically look like small threads or hairs, which are enlarged at one end. You may also see worms in your dog’s vomit or sputum.

Is it normal to see living worms after giving your dog a worming medication?

Yes, particularly in the case of roundworm infestations. Such worms are typically in the process of dying. Be sure to check out our article that explains what you’ll want to expect after worming your puppy.

Are worms dangerous for my dog?

Most of the worms discussed above will cause your dog to become ill, and several (including hookworms and heartworms) can even lead to death if left untreated.

Can people get dog worms?

Some worms and parasites that infect dogs – particularly protozoans and hookworms – can be transmitted to humans. In some cases, these parasites can cause serious health problems.

How do you get rid of dog worms?

The best way to get rid of a worm infestation is to work closely with your vet. Your vet will likely recommend a routine de-worming schedule for puppies, and he or she will advise you about treating adult dogs on an as-needed basis. However, there are several over-the-counter dog worming products you can use to treat your dog. If you’d like to treat your dog’s worm problem at home, be sure to check out our dog dewormer guide, as well as our guide to home remedies.

Are dog worms contagious to other dogs?

Most worms and protozoans can be spread from one dog to another. Two notable exceptions include heartworms, which are transmitted via mosquito bites, and tapeworms, which dogs usually contract when they inadvertently eat fleas. The contagious nature of most other worms is part of the reason it is so important to keep your dog’s environment clean – particularly when battling a worm infestation.

Dog parasites

Worms in dogs are certainly a problem you’ll want to address, but they’re a pretty normal part of a dog’s life. Just be sure to work with your vet if you believe your dog has worms or other parasites and look out for any symptoms that may indicate an infection.

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