Worms, so-called Endoparasites, are like ticks, mites or fleas, among the most common parasites that can infest dogs in their lives. There are different types of dog worms, which can cause different symptoms in four-legged friends.

Worms in Dogs

An infestation with worms can be without symptoms for the dog or with more or less severe symptoms. In the worst case, however, the worm infestation can lead to an infection. To avoid complications, dog owners should know the signs of worms in dogs to be able to act early.

In the guide, you will learn which types of worms affect dogs, which signs of worm infestation you should know and what you should do if you suspect worms in your four-legged friend or want to avoid a worm infestation.

Furthermore, so that you do not have to worry about the proper treatment in case of emergency, taking out a dog health insurance is advisable. This way, you can take care of your beloved four-legged friend instead of worrying about the vet bill.

Worms and Dogs: A One-Sided Relationship

There are relationships of mutual benefit in nature, for example, between many fungi and trees. And some parasites are no benefit to their host animal, sometimes even causing considerable harm. Such a one-sided relationship also includes the relationship between dogs and worms. Our four-legged friends gain no benefit from worm infestation.

On the other hand, the nutrients in the dog’s body ensure the continued existence of various worm species. So that you as an owner take countermeasures with deworming is undoubtedly in the interest of your pet and your own family.

Worms find their way into the dog in different ways. Contact with infectious eggs or larvae from the feces of infested conspecifics is one of them. In this case, the fecal pile can be recognizable. The resistant eggs spread in the environment. They are also occasionally carried home by the owner on his shoes or adhered to the dog’s fur. If the eggs are ingested through the mouth, they silently trigger a worm infection.

Often, worm infestation of adult animals is not externally recognizable. In puppies, however, worms can have serious consequences for health. As you will see in the video, many puppies are infected through their mothers – as in the case of roundworms. Roundworms are among the most common worms in dogs.

In the case of tapeworms, the transmission usually only occurs when the dog tends to hunt and eat prey that serves as intermediate worm hosts. This is especially true for the fox tapeworm.


What are the most Common Causes in Dogs for Infection with Worms?

Where do dogs get worms in the first place? This question usually cannot be answered unambiguously, because there are various ways in which the four-legged friends can become infected with the parasites.

This is mainly due to the fact that worm eggs can survive in nature for several months and can therefore be transmitted not only via fresh feces. It can also happen, for example, that worm eggs adhere undamaged to shoe soles and are thus brought into the home by the dog owner, where the dog can come into contact with them.

Causes of infection with worms in dogs:

  • Ingestion of worm eggs via dog feces: One of the most common causes of worm infestation is ingesting worm eggs or larvae via other dogs’ feces. Eating or licking the feces is the riskiest, but even contact with the nose can lead to infection.
  • Eating prey: Another cause of worm infestation in dogs is ingesting the worm eggs by eating prey, which serves as intermediate hosts for the worms. This can also result in infection with fox tapeworms by eating wild rodents that carry tapeworm stages.
  • Infection in the mother: Puppies can become infected with worms in the womb if the mother is infested with the parasites. In addition, puppies can also become infected with worms while suckling from their mother.
  • Attachment of worm eggs to fur: worm eggs survive relatively long in nature. If soil, sand or undergrowth with worm eggs sticks to the dog’s fur during a walk, the worms can enter the four-legged friend’s organism by licking the fur. Worm eggs can also be carried into the apartment with shoes.
  • Infection through food: Transmission with the dog tapeworm can occur when dogs are fed with insufficiently heated or frozen meat, especially offal such as lungs or liver.
  • Transmission via fleas: Other parasites, such as fleas, can also transmit worms to the dog. For example, an infestation with hookworms or cucumber nematodes can occur.  

Why do Puppies get Worms

Signs To Look Out For To Tell You That Your Dog Has Worms

Due to the different types of worms, dogs have no uniform signs of worms. Often healthy dogs with worm infestation initially show no symptoms, and the first symptoms appear when the infestation is more advanced.

If a dog has worms, these symptoms can occur:

  • Worms or egg sacs that may be seen in the dog’s faeces are the most reliable indicator that your pet is infected with worms. The best time to look for these indicators is right after your dog has finished defecating. It makes no difference whether it is dead or still living. On the other hand, the naked eye is unable to detect all species of worms that may be present in faeces. This does not imply that they are not present simply because you are unable to detect their presence.
  • Worms that may be seen moving around in your dog’s hair or congregating in the area surrounding his or her rear end are a warning flag. In particular, tapeworms will appear to the naked eye as a series of minute moving segments; after they have dried out, they will take on the appearance of dry grains of rice.
  • Scratching and rubbing the bum on the ground or against furniture or anything they can find – if your dog shows signs of itchiness around the bum area, it may be irritated by worms in the area. However, this could also be due to problems with full anal glands which are totally unrelated to worms. If you are not sure, treat for both.
  • Vomiting with visible worms – if your dog has worms, you may also see them in your dog’s vomit. Worms will induce vomit and make your dog very sick.
  • Bloated stomach or belly – This is another common symptom of worms, often seen in puppies who receive an infection of worms from their mother. Your puppy may look cute and fat but are actually taken over by worms.
  • Weakness, increased appetite, constant hunger, weight loss – If your dog has worms, the worms are pinching your dog’s nutrition. If you notice that you are feeding your dog correctly and the correct amounts and they still constantly look for food and look weak and hungry, or are even losing weight you can more than likely suspect a worm infestation.
  • Diarrhea, sometimes also bloody!
Worm Infection in Dog

Diagnosis & Treatment: What to do if my Dog has Worms?

Diagnosis of Worms in the Dogs Digestive System

If you suspect your dog has worms, you should take your four-legged friend to the vet as soon as possible. Only there can the worm infestation be diagnosed beyond doubt. To do this, the veterinarian first performs a general examination of the animal.

Blood and fecal samples provide clarity

To perform this, the veterinarian will examine blood or fecal samples from your dog. By the way, more than one examination of the feces is needed. Because your dog does not excrete eggs of the worms every time, a single negative sample can still not provide certainty.

Depending on the type, you can easily determine the worm infestation in your dog. For example, in the case of roundworms, it is common to find whole worms in the dog’s feces. In the case of tapeworm infestation, individual limbs of the parasites are repeatedly excreted. You can usually see these well with the naked eye.

The Correct Treatment for Worm Infestation in Dogs

Treatment, or prevention of worm infestation, is done by regularly deworming the dog with special dewormers. This is important to completely kill the parasites and avoid complications and health complications.

To ensure this, choosing a dewormer that is effective against the type of worms present is necessary. For example, there are special preparations to fight tapeworms and roundworms in dogs.

The veterinarian can determine which worming agent is suitable by determining the parasite. Dewormers are available in different dosage forms, such as tablets, pastes or tinctures. In which form the deworming is carried out is irrelevant to the treatment. It is important that the worming treatment is carried out properly and that the dog tolerates it well.

For example, the deworming agent is given to the dog with a treat or mixed into the food and is effective for about 24 hours after ingestion. The worms are thereby killed and excreted by the dog in the feces.

Therefore, a single treatment is usually sufficient to stop worm infestation. However, in the case of a severe infestation, a new fecal examination must be performed by the veterinarian after four weeks to check the success of the deworming. The dosage and treatment duration should be strictly adhered to in order to really kill all parasites.

De-worming Puppies

How Dangerous are Worms for Dogs?

Since most dogs are infected with worms at least once in their lives, the adverse health effects are often underestimated. Although an infection with worms in dogs is not initially life-threatening, if an infection is not treated, it can have serious consequences under certain circumstances

The severity of an infection also depends on which parts of the organism are affected by the worm infestation and how early the worms are detected.

Depending on the type of worm, the following health consequences may occur:

  • Damage to the gastrointestinal tract: Hookworms, roundworms and tapeworms live in the dog’s digestive tract, where they suck blood and can cause damage. Infestation with intestinal parasites can cause diarrhea, vomiting or an impaired utilization of nutrients in the dog. These worms are especially problematic in puppies and young animals, as they can cause growth disorders, among other things.
  • Damage to heart and lungs: Heartworms and lungworms mainly attack vital organs such as the heart and lungs and can cause severe damage there if the infection remains undetected. Therefore, you should consult a veterinarian – if signs such as coughing, loss of appetite and reduced performance are observed.

To avoid health consequences, dog owners should definitely consult a veterinarian early on if they suspect worms in their dogs. If the worm infestation is treated quickly, it usually does not come to serious diseases in the four-legged friends. 

Particularly in puppies, one should pay attention to symptoms and changes since the immune system of young dogs is not yet so strong and can fight an infection worse.  

Puppy with Worm Infection

Can Dogs Transmit Worms to Humans?

The transmission of worms from dogs to humans is generally possible and especially likely when dog owners have close contact with their four-legged friends. For example, if the dog is cuddled a lot or sleeps in the bed or on the couch, worm eggs can enter the human organism via smear infections.

Children who let the dog lick their hands or face or play outside in places where there is dog excrement can also easily become infected. Most often, humans become ill through transmitting certain types of worms, such as hookworms, roundworms and tapeworms. Such an infection can be very problematic, especially for elderly and immunocompromised people or children, and can cause severe symptoms of illness.

For example, dog or fox tapeworm infection can lead to dangerous cyst formation in the liver and other organs. This can lead to death despite elaborate therapies. Since the worm eggs survive for a long time outside the dog, good hygiene, i.e., washing hands and cleaning bowls, should always be observed to keep the risk of infection as low as possible.

If an infestation with worms has been detected in your four-legged friend, more attention should be paid to appropriate hygiene measures and quick and detailed treatment.

Parasitic hookworm Ancylosoma
Parasitic hookworm Ancylosoma

Is it Possible to Prevent a Worm Infection in dogs?

Unfortunately, there is no way to avoid a worm infestation for sure. However, you can minimize the probability of infection by observing the following points:

  • Always dispose of the dog excrement. This applies to the walk as well as to your own garden.
  • Do not let the dog eat outside.
  • Have the feces tested for worms or dewormed on a regular basis.

Generally, it is recommended that dogs with supervised exercise and contact with other dogs, be tested for worms or dewormed four times a year. If the dog has unsupervised exercise and contact with conspecifics or is used for hunting, it should be examined or dewormed more frequently.

For an individual assessment of your dog’s risk, you should consult your veterinarian.

Are Deworming Agents harmful to my Dog?

Usually, a worming cure has no side effects because the means for worming are composed in such a way that they harm the organism of the worms and not that of your dog.

A study published in 2019 shows that treatment with dewormers such as albendazole against hookworms and roundworms has no harmful effects on the composition of the gut microbiome.

Intestinal Microbiome
Intestinal Microbiome

However, in rare cases, depending on the degree of worm infestation, the agent and the dying worms cause symptoms such as gastrointestinal discomfort, diarrhea, faintness, temporary itching, hair loss, and vomiting.

Since every dog reacts differently to an active ingredient, it may be advisable to test a different agent if side effects occur. Of course, the various deworming agents should be used under veterinary supervision and with the necessary expertise.

For a permanent application, deworming agents are unsuitable since they stress the dog’s organism despite good tolerability.

A good prevention against worm infestation is a healthy organism and especially a healthy intestine, which can cope with a weak infestation of parasites alone. The dog then excretes the worms before they can infest and attack its organism.

Herbal De-wormers as a Compatible Alternative?

Apart from normal dewormers for dogs, there are now also several herbal dewormers. These are intended to treat worm infections with mixtures of different herbs and plants.

In addition to coconuts, wormwood, parsley, carrots and ginger are among the possible ingredients of such a herbal worming cure for dogs.

At least when it comes to the prevention of worms in dogs, such preparations can certainly be a good alternative that does not unnecessarily burden the organism of your four-legged friend.

What Worms are Common among Dogs?

Dogs are popular hosts of several worm species. However, the individual risk of worm infestation varies greatly and depends on several factors. These include age, exercise behavior, diet and housing conditions.

You should therefore develop a strategy against worms in your dog together with your veterinarian. The most important worms in dogs include:

The Roundworm – Toxocara Canis

The Roundworm – Toxocara Canis is by far the most common worm in dogs in the United States and is quite large, reaching up to 20 centimeters in length. According to recent studies, an average of more than 5 percent of local dogs carry roundworms of this species.

Depending on the region and age, however, the value can be significantly higher. Among puppies up to 6 months, it is about twice as high at 12 percent. The little ones are particularly at risk because roundworm infestation can lead to diarrhea, vomiting and poor nutrient utilization.

Possible consequences include stunted growth, a dull coat and, in cases of severe infestation, a thickened, painful “worm belly,” and anemia. Adult dogs often show no obvious signs of worm infection but may shed worm eggs and thus be a source of infection.

Because worm eggs are very hardy and are distributed in the environment with dog feces, up to 14 percent of feces, soil and sand samples from public parks and green spaces are contaminated with roundworm eggs.

Humans can also become infected with the worms through close contact with their pets.1

Toxocara canis second stage larvae hatch from eggs
Toxocara canis second stage larvae hatch from eggs

The Hookworm – Ancylostomatidae

Hookworms (Ancylostomatidae) are not quite as common as roundworms, averaging 2.2 percent of infested dogs, and are much smaller at 1.5 inches long.

Hookworms live in the dog’s digestive tract. They attach themselves to the intestinal mucosa and suck blood. The eggs, which are excreted in the dog’s feces, hatch into larvae. These live on the soil and can enter the host organism through the skin or be ingested through oral contact with contaminated soil or objects. Puppies also become infected through the dog’s mother.

Hookworms sometimes cause not insignificant blood loss due to damage to the intestinal mucosa. This can be particularly dangerous for small or weakened four-legged friends. Other symptoms of hookworm infestation are emaciation, fatigue and bloody diarrhea. In rarer cases, hookworms also invade through human skin and cause health problems – especially in immunocompromised individuals.

Head of a parasitic hookworm
Head of a parasitic hookworm

The French Heartworm – Angiostrongylus vasorum

The French Heartworm (Angiostrongylus vasorum) has become more common in recent years. Dogs become infected with French Heartworms when they eat slugs, mice or birds that are infected with worm larvae.

French Heartworms infect the pulmonary arteries and the right side of the heart in dogs. Thus, inflammation of the lung tissue, blood clotting disorders, loss of appetite, reduced performance or even sudden death is possible.

the puppy pug is watching crawling snail fence

The detection of Angiostrongylus vasorum infestation is done by means of a special fecal examination. Meanwhile, a blood test is also increasingly used, which can provide rapid results.

The Whipworm – Trichuris vulpis

On average, about 1.2 percent of dogs in this country are infested with the whipworm Trichuris vulpis. However, in some dog breeds, up to 30 percent are infested.

Whipworms get their name from their whip-like appearance, as they have a thread-like front end followed by a thicker rear end. Like hookworms, whipworms attach to the intestinal wall and feed on blood. A heavy infestation can cause bloody diarrhea, in rarer cases with more severe complications.

Whipworm eggs are incredibly hardy and can remain infectious in the environment for years if excreted in feces. Repeated infections are possible at any time in a contaminated area. As a result, whipworm can be a serious problem in animal shelters and kennels. In addition to regular deworming, removing the feces of infected animals is essential.

Whipworm egg under microscope - Trichuris vulpis
Whipworm egg under microscope – Trichuris vulpis

The Heartworm – Dirofilaria immitis

The heartworm (Dirofilaria immitis) is responsible for heartworm disease (Dirofilariasis) mainly in the Mediterranean region and, like the skin worm Dirofilaria repens, is transmitted by some mosquito species. 

The spread of the worms via mosquitoes is strongly dependent on climatic factors. Therefore, climatic changes can cause mosquitoes to spread as vectors to areas – they were not originally native.  The Asian tiger mosquito entered the US in shipments of used car tires from North-Asia in the mid of the 1980s

Heartworm larvae are transmitted to the dog via the bite of a mosquito. They then travel through the bloodstream to the heart chambers and pulmonary vessels. There they can develop into adult heartworms and cause severe health damage. 

Adult heartworms grow up to 30 cm long. De-worming directed against the heartworm kills the heartworm larvae and prevents further development. There are now preparations used for routine de-worming that are effective against heartworm larvae simultaneously.

Heartworm, Dirofilaria immitis, in organs at necropsy
Heartworm, Dirofilaria immitis, in organs at necropsy


Tapeworms (cestodes) are long, flat worms that live as parasites. They enter the intestines of dogs and other animals (including humans), where they hook or suck and live on the components of their host’s food. They can remain there for many years.

Usually, tapeworms have a primary host. This is the animal, often human, in whose intestine the worm lives, grows and lays eggs. In addition, other animal species serve as intermediate hosts. In them, larvae or other preliminary tapeworm stages grow from the eggs. If humans eat the meat of infected animals without having cooked it properly, we can become infected with the tapeworm.

The Fox TapewormEchinococcus multilocularis is found throughout the United States. The most crucial final host is the red fox; intermediate hosts are field mice and other rodents. Dogs usually become infected when they eat infected intermediate hosts such as mice.

Therefore, dogs with unsupervised exercise or hunting, catching prey, or eating carrion are at risk of infection. The risk of infection in humans comes primarily from the spread of foxes. However, human infection is extremely rare.

The Dog Tapeworm – Echinococcus granulosus was first documented in Alaska but is distributed worldwide. It is especially prevalent in parts of Eurasia, north and east Africa, Australia, and South America. It is most common in areas where sheep farming is done.

Humans become infected via oral ingestion of eggs through contact with contaminated soil or consuming contaminated food.

medically accurate illustration of an echinococcus granulosus
3d rendered medically accurate illustration of an echinococcus granulosus

Other Common Intestinal Parasites that are problematic in dogs


Coccidia are single-celled parasites that infest the intestine of their host. They are found practically all over the world and can infect other mammals or humans in addition to dogs.

There are several species of microscopic protozoa. When a dog becomes ill with coccidiosis, Cystoisospora canis, Cystoisospora burrowsi or Cystoisospora ohiosensis are responsible in most cases.

The infection occurs orally when the quadruped ingests the coccidia spores through an infected animal’s feces or through contact with contaminated surfaces. If the coccidia enters the body this way, they settle in the epithelial cells of the intestine. Then, they begin to multiply so that after about one to two weeks, the dog also excretes spores, which can infect other dogs with coccidiosis.


Diarrhea can repeatedly occur in dogs for a variety of reasons. One of the dogs’ most common triggers of gastrointestinal disorders is Giardia duodenalis. The pathogens are microscopic, single-celled parasites that attach themselves to the small intestine’s intestinal wall, disrupting the animals’ regular digestive processes. Young dogs, in particular, often suffer the consequences of an infestation with Giardia.

An infection with Giardia in dogs is called giardiasis and is a possible trigger for intestinal inflammation. In addition, giardiasis is a zoonosis, i.e., a disease that can theoretically be transmitted to humans.

Giardia duodenalis
Giardia duodenalis


Infection with worms can happen quickly in dogs because the worm eggs survive in nature for a long time and remain contagious. However, a worm infestation can be prevented by regular worming.

Since worms can be especially dangerous for puppies, care should be taken to prevent them from puppy age. Especially dogs with a weakened immune system can be more severely affected by an infection by worms.

Therefore, it is essential to vaccinate already puppies because vaccinations train the Dog’s immune system; thus, your Dog is usually less susceptible to serious infectious diseases.

In addition to regular deworming, it is advisable to pay close attention to the Dog, especially outside, and always consult a veterinarian if there are signs of worms in your Dog. If detected early, worm infestation can usually be treated successfully.

  1. https://www.sciencedirect.com/science/article/abs/pii/S030440171000590X


Dr. Orika Mosquera

Hello, I am Dr. Orika Mosquera Lopez graduated from the free university of colombia sectional Barranquilla as a doctor and surgeon. I work as a General Practitioner with Experience in the Emergency Department, Hospitalization and External Consultation. I love pets, i have 2 cats, Bagheera and Nhala and one Yorkshire Terrier called Princess. I care a lot about the well-being of my animals


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