Allowing domestic cats to roam outside the house can result in parasitic infection which can harm not only the cat but also its owners, according to a study.

The research analyzed more than 20 scientific studies and cats from over a dozen countries including Australia, Brazil, Canada, Germany, Pakistan, Spain, Switzerland, Netherlands, and St. Kitts. It looked at 19 different cat pathogens including those relevant to human, domestic animal, and wildlife health, such as Toxoplasma gondii and Toxocara cati.

Don't Let The Cats Out

A new meta-analysis from the School of Forestry and Wildlife Sciences at Auburn University in Alabama suggests that outdoor cats are nearly three times more likely to become infected with pathogens than their indoor counterparts. Many of the pathogens that cats carry can be transmitted to humans.

Surprisingly, the study also indicates that cats in countries farther away from the equator are more likely to be afflicted by a bug or virus if they are set free outside. Wildlife in higher altitudes also showed higher infection rate from bacteria, increasing the risks for cats in those countries.

The study yielded consistent results for almost all of the diseases, including feline roundworm, and the single-cell parasite, both of which can affect humans. The pathogens were also transmitted in various ways, from the soil, other cats, or prey such as mice and birds.

"Basically, no matter where you are in the world, keeping your cat indoors is a great way to keep them healthy from infectious diseases," Kayleigh Chalkowski, lead author of the study, told AFP.

Transmission From Animals To Humans

There is an estimate of 80 to 90 million pet cats in the United States, and 500 million worldwide.

Other domesticated animals are known to transmit disease to their owners or caretakers. Dogs can spread rabies, and cattles can pass on Cryptosporidium parvum, a parasitic disease that attacks the intestinal tract. The parasite Toxoplasma gondii has been linked to depression, seizures, and schizophrenia in humans.

To mitigate parasitic infection, the study suggests that cat owners monitor how far their cat wanders from home, and limit the number of other animals the cat may come into contact with.

Likewise, the researchers advise that kittens that have weaker immune systems than grown cats should be kept indoors.

The study is published in the journal Biology Letters.