Intestinal Parasites

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Intestinal Parasitism And Immunity of Dogs and Cats

Parasites develop more easily in animals whose individual resistances are weakened: this is particularly true for puppies and kittens but it is also the case during periods of pregnancy, delivery and lactation. The outbreak of parasites will happen preferably during these sensitive live stages.


Parasites develop more easily when the organism has not developed any immunity yet, or when there is a transient immunodeficiency. And consequently, a significant parasitism leads to a decrease in the general state as well as immune defenses.

Influence of digestive worms on the health of dogs and cats

In young animals, roundworms can cause serious disorders: diarrhea, vomiting, intestinal obstruction, swollen abdomen, delayed growth… With tapeworms, the signs are generally more discrete: deterioration of the coat condition, digestive disorders... 

Clinical signs are less noticeable in adult animals because they acquire some immunity to various parasites. However, pay attention to a dog or a cat that scratches and/or licks itself intensely in the anal area, because tapeworm contamination can cause chronic irritation in this area. Digestive tract disorders as diarrhea or vomiting can also be a sign of intestinal worm presence.

Even if your dog/cat does not show obvious symptoms of parasitism, this does not mean that it should not be dewormed! The parasite cycle continues to occur in the body and a parasitized animal contaminates its environment through the eggs it releases in its stool.

Some dog and cat parasites are dangerous for humans

Dogs and cats that come to relieve themselves in sandpits where children play represent an important source of contamination by roundworms. Accidentally ingested parasite eggs can cause serious problems in humans. One of the most dangerous parasites for humans is the echinococcus tapeworm because the larvae develop in the liver. These larvae can be harbored by dogs or cats who hunt rodents.

Deworming your dog or cat therefore helps to protect human health too.

Deworming before vaccination

For a vaccine to be effective, it is essential that the animal's immune system is competent. In general, it is preferable to avoid vaccinating a dog or cat whose immune system may be weakened: undernutrition and/or parasitism are two factors that can weaken immune defenses. 

If an animal is vaccinated without first being dewormed, it is likely that its response to vaccines will be lower than expected. This is particularly important for puppies and kittens when they receive their first vaccines. It is therefore advisable to deworm a puppy or a kitten a few days before the injections and also before the recalls. 

A puppy or a kitten will be more capable of building effective immune defenses if it has been dewormed and then correctly vaccinated.  A high quality diet, in sufficient quantity, is also indispensable for a good immunity.


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Intestinal Parasitism

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Toxocara Transmission

Roundworms in Dogs And Cats

Roundworms are the most common worms found in puppies and kittens because contamination takes place from birth! Getting rid of these parasites is important for their health but also for the health of those who live around them because accidental ingestion of roundworms eggs can lead to serious problems in humans.

Ask your vet for advice before buying a dewormer because not all are equal!

Dogs and cats contaminate themselves from birth

Initial contamination of puppies and kittens by roundworms occurs via the placenta or maternal milk, when their mother was infested by these parasites. Roundworm larvae then develop in the pup’s or kitten’s intestine and eggs are then released in the stools, contaminating the environment. By sticking to animal feet and human shoes, roundworm eggs can be transported everywhere!

Adult hunting cats and dogs also infest themselves by consuming prey that carry roundworm larvae in their tissues.

Various disorders are induced in young animals

When roundworms are very numerous, they form balls that disrupt the intestinal transit. In the event of a major infestation, these worms cause many digestive disorders. 

Parasites also prevent puppies and kittens from taking full advantage of their nutritional intake: their growth slows down and their immune defenses weaken.

Human contamination can be serious 

Every day, thousands of eggs are released into the stools of parasitized animals, which can survive 2 years in the outdoor environment! They are obviously found in the litter of the cat but also in all the places where dogs and cats can eliminate their stools. 

Children who play in soiled gardens or sand pits (as well as people who eat poorly washed vegetables) are exposed to accidental ingestion of roundworm eggs. Contamination can also occur when an infected dog or cat is cuddled and eggs are glued to his hair. The risk is greater for children as they often carry their hand to their mouths after cuddling the animal.

Ingested eggs give rise to larvae that migrate into the body and can cause serious health problems, especially if they are located in the eyes or nervous system.


The frequency of deworming depends on the age and lifestyle of your dog or cat, but it has to be done at least twice a year. Your veterinarian can help you to optimize the protocol by examining for instance a stool sample of your pet under a microscope and questioning you about your animal lifestyle. The number and type of eggs of parasites observed, as well as the hazard your pet is facing will help him to prescribe a more focused treatment.

Protecting Your Pet from Tapeworms and the Disease They Transmit

When we talk about digestive parasites in dogs and cats, we usually think of roundworms (nematodes), present in young animals. Tapeworms (cestodes) are often forgotten, whereas they are also extremely common. Tapeworms rarely endanger the lives of animals, but they can cause digestive problems and irritations that significantly affect their well-being.


The parasitic cycle of tapeworms always passes through an intermediate host that will allow the eggs to develop into infesting larvae. Dipylidium caninum is transmitted by fleas but there are many more. 

Dipylidium caninum, the most common tapeworm

Dipilydium caninum is a worm that reaches 50 cm long and a cat/dog can harbor several adult parasites in its digestive tract! Dipylidium attaches to the small intestine through its anterior extremity and feeds on the animal's intestinal content.

Tapeworms reproduce by shedding segments packed with eggs, called proglottids, which are excreted in faeces. Flea larvae feed on proglottids and carry the tapeworm eggs through their development into adult fleas. These are easily ingested during grooming, especially in cats, and the lifecycle starts again. 

When they have just been excreted, the proglottis are pink and mobile; after desiccation, they look like rice grains and they can sometimes be seen crawling around the pets’ rear or on faeces. They can be very irritating and, to soothe the itching, dogs “scoot” (or drag their bottom) along the floor. The veterinarian can also perform a stool analysis to highlight the eggs.

Other tapeworms found in pets

Pets who love hunting can pick up other types of tapeworms. Whatever the preys they consume (rodents, rabbits, lizards or even freshwater fish), they are exposed to contamination by multiple tapeworms, more or less specific to their favorite preys.

The most dangerous tapeworms are Echinococcus granulosus or Echinococcus multilocularis. A classic fox parasite, Echinococcus spp. sometimes infests the dog when it consumes contaminated rodents. This parasitic disease is relatively mild for the dog itself but seriously threatens human health. A dog that harbors Echinococcus spp. excretes eggs in huge quantities and they can end up on the dog’scoat, and then on the hands of people who are in contact with the dog. If someone accidentally ingests the parasite's eggs, larvae can develop in the liver or lungs, where they give rise to very large cysts, causing significant damage. 


If your cat goes out a lot or if your dog has frequent contact with foreign animals, regularly worming is important. Ask your veterinarian for advice on choosing a product which is really efficient on tapeworms. They do not develop any immunity against these parasites, so they can be reinfested even after being treated.

And don't forget to treat your pet against fleas all year round to limit the risk of Dipylidium contamination!

Hookworm Transmission

Hookworms are round and unsegmented worms that belong to the group of nematodes. In Europe, the most common species observed in pets are: Ancylostoma caninum (in dogs), Ancylostoma tubaeforme (in cats), and Uncinaria stenocephala (in dogs and sometimes in cats). 

Adult hookworms are found attached to the wall of the small intestine. They have teeth around their “mouth” and they pump their host’s blood. An anemia can develop in infected animals.

Dog and cat contamination

During the cycle of hookworms, eggs are passed by adult females in dog or cat feces and hatch as larvae on the ground where they become infective within 1 to 3 weeks. These larvae are found in shady, moist, sandy soil. The larvae infect the animal either by being ingested or by penetrating the host’s skin. 

Larvae that enter the host through the skin migrate to the lungs. Once there, they crawl up to the trachea, where they cause an irritation that makes the animal cough. Coughing brings the larvae to the mouth, where they are swallowed and travel to the small intestine, and mature to adulthood.

If the larvae are ingested, they travel directly to the small intestine. Some burrow through the intestinal wall and travel to the lungs through tissues. Once in the lungs, they follow the same path as larvae that penetrated the skin. 

Some of the larvae stay in the tissues, and when the host is a female and becomes pregnant, these encysted larvae become active at the end of the pregnancy; they travel to the mammary glands, where they can pass in the milk to the newborn kittens and puppies.

Human contamination

Immature hookworm larvae may accidentally penetrate the skin of human people. Adults and children can be infected by walking barefoot on beaches or sand pits, where dogs and cats have been allowed to roam freely and contaminate the sand with infected feces. 

Fortunately, when the larvae of these parasites penetrate the human skin, they cannot go any further. For the hookworms, human species is an atypical host and larvae cannot penetrate into blood vessels and travel to the lung. However, a disease called cutaneous larva migrans or creeping eruption develops on the skin. The infection can be detected through papules or even pustules (reddish bumps containing pus) that develop in areas where the skin is very thin: on the abdomen, between toes… Since man is a dead-end host, the lesions can usually disappear spontaneously within a few weeks or a few months. 


Hookworm contamination is rather common in hunting dogs, when there is a poor hygiene in the kennel. Regular deworming treatments in dogs and cats will help to prevent hookworm infestation.

Protecting your pet from Dipylidium caninum

Dipylidium caninum is the most common tapeworm in pets. (Despite its name, it is hosted by cats and dogs). Worming products targeted against roundworms are not always active against Dipilydium, so it is better to know how to spot its presence and, if necessary, treat the animal properly.

Contamination with this tapeworm involves fleas and it is therefore pets that are not treated against these insects that are most at risk. Lice can also transmit Dipilydium but they are rare in pets.

How can I know whether my pet is contaminated with Dipylidium?

Dipilydium is a tapeworm and its body consists of a hundred of segments, each measuring 8 to 10 mm long and 2-3 mm wide. As an adult, this parasite lives for 1 to 3 years and it is hermaphrodite: a single worm can therefore produce eggs. These are released inside segments (proglottids). Whole segments are rejected with stools. They disintegrate quickly and the eggs are then scattered in the environment.

You may see Dipylidium rings on the stool, at the edges of the anus and sometimes in your pet's sleeping quarters: they look like rice grains and are very mobile. Because of licking, they can sometimes be seen on the coat of the pet. 

Dipylidium caninum can potentially contaminate humans

Children are sometimes infested with Dipylidium when they put their fingers to their mouths, right after they have cuddled the pet or played in its basket. This contamination is not dangerous to their health (usually it only causes itching) but the psychological impact on parents is often extremely negative!

How does the dog/cat get infested? 

Dipylidium needs an intermediate host to contaminate the dog or cat. These are flea larvae that live in the animal's environment before turning into adult fleas and jumping on a passing cat or dog. Flea larvae shelter in gaps close to the pet's litter, basket or sleeping quarters, and they can ingest eggs removed by the animal. Once ingested by flea larvae, Dipylidium eggs grow inside the insect and can live 6 to 12 months in this intermediate host. The pet contaminates itself by swallowing fleas that live in its coat, by grooming daily or biting because of itching. Dipylidium larvae are then released into the cat's digestive tract and become adults in about three weeks. 


The Dipylidium is a major source of itching in infested pets. As their anus is irritated, they lick intensely under the tail and dogs sometimes try to relieve themselves by rubbing the posterior against the ground, a behavior called "the sled sign ". However, it is rare that this tapeworm causes digestive problems or affects the general condition of the animal.

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