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Tierarztpraxis Hetzgasse

This article was written by TOBALIE in cooperation with Tierarztpraxis Hetzgasse

So tiny, yet so unpleasant and sometimes threatening for our beloved pets: endoparasites. A single one of these annoying specimens is unlikely to cause much damage. However, if they multiply into a small army in the organism, it can be quite annoying for our darlings. Which pararasites are to be distinguished from each other and which health effects are to be feared in each case? you can read about it in the following lines.

What are endoparasites and which ones are there?

A parasite is an organism that usually feeds on larger creatures (the host: e.g. human/animal) and their body fluids. Skin scales or similar, generally any kind of organic material, also serve as a source of food for these small parasites. A distinction can be made between endo- and ectoparasites. The former infest the inside of the body, whereas ectoparasites live on the skin. In veterinary parasitology, a basic distinction is made between protozoa and worms. Both types of parasites can attack different organ systems of our pets and lead to various health problems. 

There are countless parasites. The following list is intended to give you a small overview of endoparasites that are common and dangerous in our country.

Single-celled parasites


Are one of the most common endoparasites, which occur especially in young animals. They are very resistant in the environment and are transmitted for example via contaminated water points. At home they often stick to blankets, feeding bowls and toys of your four-legged friend. Therefore, in case of an infestation, treatment of the living environment (e.g. with a steam cleaner) is part of the therapy. A transmission to humans is also possible (zoonosis).


These are parasites of the digestive tract that cause diarrhoea and are more common in young animals. They also occur in rabbits and should be considered as diarrhoea pathogens. They are also very resistant in the environment.


Are unicellular blood parasites that attack the red blood cells and can lead to life-threatening conditions (anaemia). They are transmitted by certain types of ticks, so effective protection against so-called ectoparasites is also crucial.

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Multicellular parasites


Roundworms or hookworms are parasites of the digestive tract and look like cooked spaghetti. Especially young animals are affected and can cause a bloated belly, diarrhoea and emaciation. As puppies are usually infected via the mother’s milk, proper deworming of the puppy should be considered with suitable aids. In the case of a dog roundworm, transmission in the womb is even possible during pregnancy. Worm eggs excreted with the faeces need a certain “maturation time” in the environment until they become a source of infection, but are then potentially contagious to humans.

Dipylidium caninum (Sort of tapeworm)

This tormentor got its name from the shape of its limbs, which are attached to each other and can actively emigrate from the intestines of the pet. The eggs themselves are able to survive in the environment for a long time. Intermediate hosts in the life cycle are fleas, which transfer the worm stages to your pet. The therapy of a flea infestation should therefore always include the appropriate deworming of your pet. This is also contagious for humans.


Among other things, some species of snails act as intermediate hosts in their life cycle, which your pet has to eat in order to become infected with these worms. But be careful, it does not always have to be an “active feeding” of snails, even the “accidental” ingestion of very small snails during the grass-feeding can cause an infection.


Are transmitted by mosquitoes, mostly in warmer climates. The heartworm (Dirofilaria immitis) enters the heart and lungs via the large blood vessels and matures there into a worm up to 30 cm long, which then releases microscopic larvae into the blood – the cycle starts again. If not treated, an infection can be fatal. 

Skin worms/eyeworms

In the meantime they are unfortunately also to be found in our latitudes. They are transmitted by mosquitoes and fruit flies. The worms, which can be up to 2 centimetres long, can cause permanent damage to eye tissue. Certain deworming agents are used to eliminate the larvae present in the blood during development. Zoonosis possible.

What can you do?

Regular and effective deworming is particularly important to ensure the health of your pet. Depending on your pet’s living conditions (e.g. a lot of contact with other animals of the same species), it is best to bring a faecal sample to your vet about 4 times a year, who will examine it for possible endoparasite infestation. If the test result is positive, there are fortunately various preparations (depending on the type of parasite) that can be administered. 

In case of digestive problems, bloated abdomen, recurrent diarrhoea, however, unicellular parasites should always be considered as pathogens, as these are not eliminated during the standard worm treatment. Unfortunately, deworming is never preventive, so your pet can get infected again immediately after deworming. Observe your animal and collect faeces (preferably from 2-3 heels of faeces, as the parasites are not always eliminated.


Endoparasites live a life as parasites. They infest the inside of our beloved pets’ bodies and can cause enormous damage. Fortunately, there are medicines that can help your pet get back on its feet. However, always remember to check your pet’s excrement regularly, then you can save yourself and your darling a visit to the vet.