They've already got a bad reputation for using flowerbeds as their toilet and sharpening their claws on the furniture - and now it looks like scientists have come up with another reason to put people off cats.
French scientists from the CNRS research institute in Montpelier have found that a parasite spread by cats could almost double their owner's chance of developing brain cancer.
The parasite, Toxoplasma gondii, is carried by about a third of the world's population. Often it causes no symptoms, but it can be fatal to unborn babies and can damage the nerve systems of people with weak immune systems. It has also been linked to personality changes in people and animals.
Toxoplasma gondii can only breed inside cats, which then pass their microscopic eggs in their faeces.
The new study shows a positive correlation between rates of infection by T. gondii and brain cancer incidence around the world.
Researchers collected global data on brain cancers in men and women and compared them to figures on T.gondii prevalence.
They found that cancer rates went up with greater exposure to the parasite.
Across the range of infection prevalence, from four per cent to 67 per cent of the population, T. gondii was associated with a 1.8 fold increase in the risk of brain cancer.
The scientists, led by Frederic Thomas, wrote in the Royal Society journal Biology Letters: "We feel our results are sufficiently strong to propose that T. gondii potentially increases the risk of brain cancer in humans."
Previous research had already linked the parasite to brain tumours in animals.
Chief causes of infection in humans are consuming undercooked meat, especially lamb, pork and venison, and ingesting water, soil or anything else contaminated by cat faeces.
The scientists added: "Clearly, further research is necessary to determine the proximate links between T. gondii and different types of brain tumours and to investigate a mechanism of action.
"Establishing a link between T. gondii and brain cancers could open the door to potential means to reduce cancer risk."
Source: Telegraph & AOL