See what the cat has trailed in: parasites

Pets can contract pests of insects and ticks, prey, earth or other animals and can transmit them to humans, domestic animals or wildlife. Dogs can cause rabies in humans, and cows can cause in them a parasite called Cryptosporidium, responsible for diarrhea. But dogs often do not go out with their owners on a leash, and cows usually can not snuggle into our sofas.

Cats lead different lives. They can go hunting alone and come back for a nap on their knees or the bed of their person. And the diseases that cats can spread can be quite virulent, from fever caused by the claws of the cat to the parasite called toxoplasma gondii, the litter parasite that doctors tell pregnant women and immunocompromised people to avoid. Cats can also transmit feline immunodeficiency virus, which makes them more vulnerable to parasites, and pass it on to other cats, even cougars.

For Ms. Chalkowski, the inner / outer dichotomy of cat life has provided an opportunity to better understand how exposure to the environment can put them at risk.

She and her team compared data from 21 studies – in countries ranging from the United States, Europe, and Australia to Pakistan, Chile, and Brazil – documenting parasitic infections in pet cats living strictly inside or outside, excluding wildcats. They were also interested in particular pests, such as those mentioned above, that could spread to other animals.

"During many different studies, with so many different parasites, in as many different countries: No matter where you keep your cat indoors, it reduces the risk of parasitic infection," said Ms. Chalkowski .

And the risk of picking up parasites has increased at the highest geographical latitudes. This was surprising because, in general, there are fewer parasites in the northern regions, particularly in the Netherlands, Germany and Great Britain. The researchers do not know why this could happen, even though it is also known that rats, common prey of felines, also carry more diseases in northern latitudes.

Some see depriving a cat of its prey by keeping it cruel inside. But others say to put them outside for doing what they want is cruel: outdoor cats are frequently run over by cars. Some are eaten by predators. And, as predators themselves, cats can kill birds or other species that nature's defenders want to protect.