Pet cats that are allowed to go out of the house are likely to become infected with parasites or pathogens about three times more than those that are confined inside the house as reported in the Royal Society journal Biology Letters.

Cat owners should also take note that cats can transmit some of those diseases that they have to humans. Also, studies show that the father the cats are from the equator, the more likely they are to have bugs or viruses if they spend time outside of their owner's house.

"Each degree in absolute latitude increased infection likelihood by four percent," said lead author Kayleigh Chalkowski, a researcher at the School of Forestry and Wildlife Sciences at Auburn University in Alabama.

"You think of tropical regions as just having more wildlife, more parasites," she told AFP. "But it turned out that latitude had the opposite effect."

To settle the ongoing indoor versus outdoor question about pet cats once and for all, Chalkowski and his colleagues went through almost two dozen studies from the past years in which the prevalence of one or more disease was compared across exterior and interior environments.

The new study released looked at 19 different cat pathogens that are found in more than 12 countries including Canada, Spain, Switzerland, Australia, Germany, Brazil, Pakistan, the Netherlands and St. Kitts.

 "This is the first-time outdoor access as a risk factor for infection in cats has been quantified across a wide range of geographic locales and types of pathogens," Chalkowski said.

The effects were seen as consistent for almost all of the found diseases, including the single-cell parasite that causes toxoplasmosis and feline roundworm, both of which can affect and infect humans.

This study's result is held true regardless of how they were transferred to humans, whether from other cats, soil, or prey such as birds and mice.

 "Basically, no matter where you are in the world, keeping your cat indoors is a great way to keep them healthy from infectious diseases," Chalkowski said by way of summary of the study conducted.

This is especially good advice, she added, "considering that many of the pathogens cats carry can actually be spread to humans".

Other pet animals that can transmit diseases to their owners are dogs, known to spread rabies, and cattle, that is known to carry Cryptosporidium parvum which is a parasitic disease that can attack the intestinal tract.

Cats were first drawn to the human communities in search of rodents and they were then domesticated around 5,000 years ago. In ancient Egypt, they were linked to gods and they were also featured in numerous ancient hieroglyphics. There are around 90 million pet cats in the United States alone and there are around 500 million pet cats worldwide.