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Why does my cat have parasites if he doesn't leave the house?

But this is not so. In our day to day, in veterinary clinics, we see cases of cats with parasites . We are going to see what types of parasites we must prevent and why.

What are parasites?

Parasites are organisms that need a host (in this case the cat) to feed and survive.

When we talk about parasites in cats, we usually differentiate between internal and external. Internal parasites can live in the intestine, lungs and heart, while external parasites can be found on the surface of the cat (skin, ears…).

Climate change and displacement due to the travel of our animals has caused diseases that were not previously considered a problem in certain areas to become so.

In order to understand why my cat, a house cat, who does not leave the house and who, on many occasions, does not have contact with other animals, may have parasites, we are going to see the most important ones and how they can affect their health.

internal parasites

This type of parasites, also called endoparasites , can be found in different parts of the body, not only in the intestine, as is often thought. For this reason we will divide them into:

  • Intestinal parasites . Among them we can find coccidia, Giardia spp, Toxocara spp, Dipilidium spp, Tritrichomonas fetus and different types of tapeworms, some of them presenting zoonotic potential . That is, it can infect people and cause disease depending on the immune system they present. Children, the elderly and people who are immunocompromised (with cancer, debilitating chronic diseases or those that affect their immune system) are at higher risk.

As relevant data, studies have been carried out in public parks in children’s sand play areas, frequently observing the presence of Toxocara spp .

  • Lung parasites. Aelurostrongylus abstrusus is the most frequent and sometimes underdiagnosed. Cats that have access to the outside have more chances of contagion, but we should not think that going outside is only going outside. Having access to a small patio, garden, terrace can also have its risks, since this parasite is transmitted through snails and slugs.

It lodges in the bronchi and bronchioles of the lung, producing a more or less severe inflammation depending on the number of parasites found. This inflammation will cause coughing, which will be the main symptom that we will see in our cat.

  • Dirofilaria or heartworm. These worms, which are most often diagnosed in the heart of the dog, are associated with pulmonary thromboembolism in the cat. Occasionally causing sudden death.
  • Other parasites that we can also find in our cat are Toxoplasma spp, Leishmania spp, Hepatozoon spp, Babesia spp that, as we will see, we can easily prevent

external parasites 

  • They can be the cause of bites, as it happens to us, and they can also be transmitters of parasites such as dirofilaria or leishmania, which is also diagnosed in cats.
  • They are not only parasites by themselves, but they are also transmitters of others such as Dipilidium spp .
  • Ticks , less frequent in cats that do not have access to the outside
  • Mites that can appear in the ear or on the skin. Ear mites are quite common and cause a very strong itching.

So how do these parasites get to my cat if he doesn’t leave the house?

These parasites can enter through the window (for example mosquitoes) or be the carriers through clothing , for example in the case of Toxocara spp eggs. We have even had cases where they have picked up fleas from the neighbor’s dog by going out on the landing and rubbing themselves on the doormat.

As we have seen, our cat can be in contact with these parasites to a greater or lesser extent , their presence being always more frequent in cats that have access to the outside. For this reason, we must plan, together with the veterinarian, a prevention plan.

How to treat them and above all prevent them

Treatment will largely depend on the parasite in question. We must know that there are some diseases that can be fatal and that with proper prevention we can avoid reaching that point.

The prevention plan will depend a lot on the type of life of the family. A family with more than one animal at home, dog, cats, will not be the same. If the family is fond of Mt. If the animals live with small children, the elderly or people with immunity problems.

Based on these variables, veterinarians will carry out a personalized preventive plan for each family that will include internal and/or external deworming.

As an alternative to routine internal deworming, we can carry out serial stool tests to detect the presence of eggs. Although we must know that if the number of eggs is below the detection range by the analysis, the result may be negative, but there is infection. It is what we call a false negative . The result is negative, although the cat is really infected, and as we have seen, there are some zoonotic parasites that can affect people, especially children, the elderly and immunocompromised.

It is for this reason that the prevention of parasites must be proposed by the veterinarian, personalized for each cat and each family, and reviewed at least once a year, since conditions may vary.


Gruffydd-Jones, et al (2013). Giardiasis in cats: ABCD guidelines on prevention and management. Journal of Feline Medicine and Surgery, 15(7), 650-652.
Vogt, A. H., et al (2010). AAFP-AAHA: feline life stage guidelines.
Miró, G.,et al (2020). Survey of Spanish pet owners about endoparasite infection risk and deworming frequencies. Parasites & Vectors, 13(1), 1-10.

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