New research shows that fluffy, cuddly kittens may be infecting millions of Americans with a nasty parasite scientists are starting to link to mental illness.
The parasite, Toxoplasma gondii (T. gondii), is the most common parasite in developed nations. Carried by cats, the parasite can infect any warm-blooded animals, with the Centers for Disease Control and Prevention estimating more than 60 million people in the U.S. alone may be infected.
While most people would never show any symptoms of having it, those with weaker immune systems have long been known to get an illness called toxoplasmosis, which can result in fetal development disorders, miscarriages, blindness, flu-like illness, and in extreme cases death.
While it has also been somewhat associated with mental disorders, namely schizophrenia and bipolar disorder, two more studies have explored the relationship much deeper than before.
The most recent study, conducted by researchers at Johns Hopkins University School of Medicine and published in Schizophrenia Research, compared two previous studies linking childhood cat ownership and schizophrenia later in life, with an unpublished 1982 survey on mental health.
The results indicated that cat exposure in childhood could be a risk factor for mental disorders later in life.
"Cat ownership in childhood has now been reported in three studies to be significantly more common in families in which the child is later diagnosed with schizophrenia or another serious mental illness," the authors said in a media release.
A second recent study conducted at the Academic Medical Centre in Amsterdam analyzed the findings of 50 studies to examine if T. gondii infection is associated with mental disorders.
The analysis showed those infected with T. gondii were almost twice as likely to develop schizophrenia than those who were not. They also linked infection with addiction and obsessive-compulsive disorder.
"In schizophrenia, the evidence of an association with T. gondii is overwhelming," the authors said in a news release. "These findings may give further clues about how T. gondii infection can possibly [alter] the risk of specific psychiatric disorders."
According to The Humane Society there are 75 to 80 million house cats and another 30 to 40 million stray cats the United States. Outdoor cats are more likely to carry the disease.
"Children can be protected by keeping their cat exclusively indoors and always covering the sandbox when not in use," the CDC recommends. The agency also suggests changing the cat's litter box daily, as T. gondii only becomes infectious 1 to 5 days after it is shed in feces.
Health officials also recommend that pregnant women avoid cleaning litter boxes due to being more susceptible to the disease.