Symptoms of Worms in Dogs: First Lesson in Canine Clinical Parasitology

Symptoms of Worms in Dogs
Wyatt Robinson
Written by Wyatt Robinson

Speaking of worms in dogs and the symptoms that they can cause in the canine body, we must bear in mind that in most of the cases the symptoms may be absent until worm infestation makes a greater progress. That is the main reason why it is recommended to provide regular anti-parasitic treatments and regular coprological analysis of dog’s excrement in order to detect the presence of worms in the dog’s body, as well as identification of type of worms present.

This is certainly of great importance not only for the dog’s health but also for the health of the people who come into direct or indirect contact with the dog because some of the types of worms we are speaking about can also infect people and cause damage to human body.

When we talk about the symptoms of worms in dogs they can be of different characteristics depending on which type of worms is causing them and how strong the invasion is, or with what number of parasites in a given moment the canine body is dealing with. For example, bloated stomach, lack of appetite, weight loss and diarrhea can be symptoms when stronger infestation roundworms. Restlessness, abdominal pain and itching in the area of the anus are most common symptoms of the presence of tapeworms.

Dehydrated dog with worms

Whipworms can cause bloody feces, anemia, dehydration and weight loss. Hookworms usually cause bloody feces, rectal bleeding and anemia. Cough, high blood pressure, weakness and possible congestive heart failure can be some of the signs of heartworm disease in dogs …

Canine clinical parasitology and types of worms in dogs

Worms, the intestinal nematodes, are the most common parasites in the intestinal tract of the dogs. The most important worms belong to the family Askaridae and the most commonly found type in dogs is Toxocara canis, which is the most important because of the possibility of human health damage.

Toxocara canis

T. canis has a complex development cycle, and dogs can be invaded (infected) in several possible ways.

Adult worms live in the small intestine, and the infested (infected) animals excrete daily thousands of eggs and worms through their feces that contaminate the environment. The earliest 10-14 days (2-7 weeks depending on the temperature) after being thrown in the environment, the produced eggs become invasive and can invade new animals or humans.

This fact is very important for public health because it tells us that people cannot become infected by direct contact with a dog but must get in touch with old feces in which eggs of the worms are present. It tells us again how important it is that people become aware of the importance of collecting droppings behind their dogs.

Toxocara canis

Young dogs are invaded through water or food that is contaminated with eggs and the development of the invasive larvae continues in their digestive system. Larvae from eggs are released into the small intestine, and migrate through the mucosa of the intestinal wall and liver via the blood stream to the lungs. The sputum from the lungs containing the larvae reach the pharynx where they are swallowed. In the small intestine the larvae mature to adult worms that again lay new eggs and contaminate the environment.

However, when the eggs with the invasive larvae are consumed by older animal, the larvae migration may end up in the liver, the muscles, in the connective tissue, the kidneys and many other tissues where crossing the stage mode, for a period which can last several years.

When a pregnant bitch is infected with larvae in the last third of the gestation period (about 40 days of pregnancy), the fetuses can be invaded through the bloodstream and through the placenta. When the puppies are born, the sputum with larvae reaches the pharynx where they are swallowed up in the small intestine and mature into adult worms.

Some larvae migrate to the mammary glands and through the milk they pass on to the puppies. Thus puppies are invaded in the uterus or via the milk, nematodes could be found in the intestine of one week old puppies.

A dog can be invaded through the holder (a rodent) when he eats a rodent that carries a cocooned larva worms in the body. In the bowels of the dog larvae digestion released from the capsule, migrate through the wall of the intestine to the liver and other tissues, and completes its development cycle in the same way as with invading through food that is contaminated with feces of infested animals.

Four weeks are required for the development of the adult stage in the intestines and the new generation of eggs in the feces.

Toxocaris leonina

T. leonina has a simpler development cycle. The adult worm parasites in the small intestine and there it lay eggs that are excreted through the feces. The eggs become invasive 3-6 days after launching in the environment. The animals get invaded through the food that is contaminated with the eggs of the worms. The migration of the T. leonina larvae is limited to the intestinal wall, while the galactogenic and transplacental transmission have not been recorded..

Rodents can be used as carriers after they have ingested contaminated food in their digestive system where larvae develop from eggs and migrate around the body of the rodent. If a carnivore eats invaded rodent, larvae release in the intestine and they continue their development into the adult stage.


The earthworms are consuming nutrients in the digestive system of the host and they disrupt the digestion and cause damage to the intestinal wall. In a case of weaker invasion of worms, animals may not show symptoms, while in animals with a strong invasion of earthworms can be noticed thinness, the animals have fur with brittle hair dull and often (especially in puppies) have inflated belly.

Signs of anemia can be present, diarrhea, vomiting and constipation can occur, and in rare cases it can lead to intestinal obstruction. As a result of migration by the lungs in young animals can occur bronchitis and pneumonia.

Diagnosis / prevention

An objective diagnosis can be performed through examination of the feces and finding eggs in the feces. In dogs that vomit, it is possible that the owner will notice worms in the gastric content, and very often in dogs with strong invasion of earthworms the warms can be seen in the feces.

The presence of worms in young puppies is a common occurrence. It is believed that there is almost no puppy that is not contaminated with worms. The usual mode of transmission of earthworms in puppies is transmission through the placenta from the mother to the offspring. Puppies therefore must be treated against worms for the first time as early as at the age of 2 weeks of birth and repeat the treatment every 2-3 weeks till the age of 3 months.

Adult dogs need to be treated against worms 3-4 times a year, or every 3 to 4 months.

The risk to human health

People can be invaded through an intake of eggs with invasive larvae present in the environment contaminated with dog feces. Children are especially in a danger in public parks and sandboxes. As previously stated, the eggs that are found in the feces in the environment must spend 10 to 14 days to become invasive and that’s why the possibility of direct transmission from dog to human is extremely low.

If a man swallows an infectious egg of T. canis larvae, that is called visceral larva migrans. It will never develop to adult worm in the human body, but due to migration by the body (liver, lung, eye, brain) it can cause serious mechanical damage.

In milder forms of the symptoms are usually minimal and the disease may go unnoticed. In severe cases, depending on the affected organs, there is fever, cough, bronchitis, enlarged liver, rash, swollen lymph nodes, «larva migrans ocularna» (larvae in the eye that can lead to blindness), and if the larvae end up in the brain are also possible interference central nervous system.

Although toxocarosis in humans can be a serious disease, luckily its incidence is rare. The most important thing is that pet owners, especially children, must take care of the usual hygiene rules and that owners carry out regular anti — parasite treatment of their pets.

Proper and regular administration of anti — parasites therapy and appropriate hygienic habits of every dog owner will ensure your pet’s health and also to protect your health.

Tapeworms are flat worms that have segmented — articulated structure, and they parasite in the small intestine of dogs and cats. They consist of a head and neck made of a certain number of segments (articles). The head of the tapeworm is attached to the intestinal wall of the host animal, and the extension of the neck continuously creates new articles while they are at the end, once they have reached a certain maturity released. Mature tapeworm segments, which are ejected through the feces, contain a large number of eggs.

Dog worms tapeworm

The mode of transmission varies depending on the type of tapeworm and its development cycle. With a host whose gut parasites adult tapeworm, the development cycle of these parasites includes temporary hosts (fleas, rodents and domestic animals such as, sheep and pigs).

There are several types of tapeworms that parasite in dogs and cats, and the CASC to find: Dipylidium caninum, T. taenaeformis, T. pisiformis, Echinococcus granulosus and E. multiocularis.

The adult tapeworms in the intestines dog will rarely, depending on the degree of invasion, the age and condition, cause serious problems, and clinical signs. With strong invasion is possible to notice pain in the abdomen dog. Animals sometimes vomiting, and articles in the area of the anus encourage the animal to lick and bite in the area.

Most dogs pets today eat prepared foods and have little availability to eat natural prey, which interrupted the natural connection of the hunter and the prey on which is based the development cycle of most tapeworms and is thereby reduced and the incidence of invasion. Anyway, these animals can be infested with tapeworms Dipylidium caninum through fleas.

The nutrition of dogs and cats with raw meat and entrails of domestic herbivores is a direct risk for the invasion with these parasites. The dogs in rural and suburban areas who move out of the yard can be made available to various small rodents, which represents an additional risk for invasion with tapeworms.

Dipylidium caninum

The most common tapeworm of urban dogs and cats is Dipylidium caninum. Adult stages of D. caninum parasite in dogs, cats, foxes, and occasionally in humans. The life cycle of a tapeworm begins when an article filled with tapeworm eggs gets through the feces into the environment.

Dipylidium caninum

The egg that is eaten by a broker (a flea larvae) develop into invasive stage of tapeworm — cisticerkoid. Dogs and cats can invade when they eat flea containing cisticerkoid. The Cisticerkoid develops insto an adult tapeworm in the intestines of a dog or a cat within the next 2-3 weeks and the cycle starts all over again. Adult stages of tapeworms in the intestines of the host can live up to 3 years. Dried segments that look like grains of rice are normally found in the hair around the anus. Their finding is the most common method of diagnosis of these parasites.

Echinococcus granulosus

The small canine tapeworm Echinococcus granulosus lives in the intestines of dogs but requires intermediate hosts. Under natural conditions, the development of this tapeworm is linked to the food chain between hunter and prey and herbivores and carnivores. Herbivores and omnivores can invade the intake of food or water contaminated with feces of carnivores (dogs).

Echinococcus granulosus

In the intermediate host of the eggs hatch oncospheres to reach via the bloodstream to the liver or lungs, and possibly heart and other organs, where they form a cystic formation (hydatid bubble) in which the larvae develop new tapeworms. Carnivores can invade when they eat the intestines of animals which are carriers of a hydatid bubble. When cysts are eaten by the ultimate bearer, the infectious stages develop adult tapeworms. The adult tapeworms attach themselves to the intestinal wall and can live for up to 2 years.

Echinococcus multilocularis

In dogs, Echinococcus multilocularis, occurs much less frequently. This tapeworm is found commonly in wild canids, and it is characteristic that small rodents play the role of intermediate hosts in its development. Although rare in dogs, this soap opera is a problem of public health because it can cause serious health problems in humans.

Diagnosis / prevention

The diagnosis is based on finding proglottides or eggs in dog’s feces. The most famous therapeutic and preventive worm medicine for dogs is praziquantel, which is an integral part of most of anti — parasite agents intended for treatment of intestinal parasites.

Echinococcus multilocularis infographic

Since the drug kills only adult stages of tapeworms, and does not have an effect on the eggs, it is necessary after the treatment within 48 hours to perform safe disposal of the feces of the treated animals without allowing any contact with other animals. In the suppression of the invasion with Dipylidium caninum in dogs and cats in addition to anti — parasite treatment of internal parasites, it is important also to conduct and protection against external parasites (in this case the dog flea).

If you’d like a more natural approach to treating your dog for these infestations, consider reading our article on home remedies for dogs with worms.

The risk to human health

People can also serve as intermediate hosts for both species of Echinococcus. One acts as the transition of the holder, and may invade the intake of food or water contaminated with feces of dogs with echinococcosis or having direct contact with a dog that has tapeworm eggs dried on the hair.

Echinococcosis can cause serious health problems in humans. Signs of the invasion can occur several years after the infection. The danger does not represent tapeworms them self , but hydatid bubble that forms in the body and puts pressure on the surrounding organs, and it is possible allergic reaction to the content of the hydatid cyst liquid bubble. If there is a rupture of cysts may develop anaphylactic shock. The disease is treated antiparasitic drugs and surgical removal of hydatid cyst liquid bubble.

Today, much more common, but less dangerous is the dog tapeworm Dipylidium caninum. Dogs and humans may be hosting a tapeworm Dipylidium caninum (as opposed to the transitional holders with echinococcosis), while the intermediate holder for Dipylidium caninum is the dog flea. Invasion in humans occurs when they eat a dog flea that is the holder of a tapeworm larvae. Symptoms include diarrhea, cramping and irritation (itching) in the area of the anus.

Prevention of an invasion of tapeworms in humans is a good hygiene (it is always recommended to wash your hands and vegetables before eating) and providing regular anti — parasite therapy for pets ( against intestinal and against external parasites).

If you’d like to learn more, we have a great in-depth article on whether humans can contract worms from dogs.

The key points in the protection against internal parasites

Because of the health problems that parasite infestations can cause in our pets, as well as the health problems that certain stages of these parasites can cause in humans, it is extremely important that pet owners to be aware of their responsibilities. Regular administration of anti — parasite therapy, following the instructions on the application and the need of safe disposal of feces after treatment, as well as responsible behavior in public spaces, the possibility of serious health problems caused by these parasites will become minimal.

Oral treatments for parasites

Due to these different types of worms that can infect your dog, it pays to know which treatment options are available. To learn more, please read our article on the treatment for worms and parasites in your dog.

Proper and regular administration of anti-parasite therapy and appropriate hygienic habits will ensure pet’s health and protect your health as well.

About the author
Wyatt Robinson
Wyatt Robinson

Wyatt Robinson had a great 25-years career as a veterinarian in United Kingdom. He used to be a member of British Veterinary Association and worked in 3 pet hospitals in London and Manchester. He is shining when he sees his pets healthy and full of energy and it is his duty to help other dog owners to keep their best friends full of life.