Can your cat cause mental illness? Facts about the parasite toxoplasmosis

With cats both cute and grumpy ruling the Internet and with cat ownership at a solid 47 million American households, it's no wonder that a study suggesting cat ownership might contribute to mental illness catches our undivided attention.

But can your cat really make you crazy? Research has linked growing up with a cat in the household to mental illness, including schizophrenia, later in life. This isn't due to any cat voodoo, but instead by a parasite transmitted by cat excrement called Toxoplasma gondii (T. gondii). A study published in Acta Psychiatrica Scandinavica in April 2015 found that "T. gondii infection is associated with several psychiatric disorders and that in schizophrenia, reactivation of latent T.gondii infection may occur."

study published in the June 2015 issue of Schizophrenia Research "suggested that cat ownership in childhood is significantly more common in families in which the child later becomes seriously mentally ill. If true, an explanatory mechanism may be Toxoplasma gondii."

More recent research in the journal Psychological Medicine suggested that there was some debate on the earlier findings, and that people exposed to cats were at no increased risk of psychosis, according to a report by Scientific American. Still, there is enough evidence to suggest that people should be a bit concerned about cat feces leading to an increase in schizophrenia.

Only worry a little about the cat-crazy connection

The idea that your cat is a big risk factor for mental illness is a "major misconception,"Dr. E. Fuller Torrey, associate director of research at Stanley Medical Research Institute and the author of an article published in Schizonphrenia Research, explained to "It is a minor risk factor. For example, it increases chances of getting schizophrenia from 1:100 to 2-3:100."

Also keep in mind that you can't pick up T. gondii just by petting your cat. The most common way it transfers from cats to humans is via handling feces and then accidentally ingesting the parasite (for example, by touching your face before washing your hands).

Also, cat feces is not the only conduit for toxoplasmosis, according to the CDC.

Cat lovers can also get toxoplasmosis in the following ways:

  • Eating undercooked, contaminated meat (especially pork, lamb, and venison).
  • Accidental ingestion after handling uncooked, contaminated meat and not washing hands thoroughly (Toxoplasma cannot be absorbed through intact skin).
  • Eating food that was contaminated by knives, utensils, cutting boards or other foods that came in contact with raw, contaminated meat.
  • Drinking water contaminated with Toxoplasma gondii.
  • Mother-to-child (congenital) transmission.
  • Receiving an infected organ transplant or infected blood via transfusion (though this is rare).

Signs and symptoms of toxoplasmosis

A peculiar aspect of Toxoplasma gondii infection is that many people are not even aware they have it. Infants born to mothers who were newly infected with Toxoplasma gondii during or just before pregnancy and those with severely weakened immune systems, are the most likely to be infected.

The symptoms can be very mild, or more like a flu, with swollen lymph glands or muscle aches and pains that last for a month or more, according to the CDC. The public health organization notes that severe toxoplasmosis develops from an acute Toxoplasma gondii infection or a toxoplasmosis incident from earlier in life that reactivates. Those severe cases are much more common in people with weaked immune systems, though the associated eye damage can occur in people who have healthy immune systems.

The CDC describes the signs and symptoms of ocular toxoplasmosis:

  • Reduced vision
  • Blurred vision, pain (often with bright light)
  • Reddened eye and sometimes tearing

The CDC refers people to an ophthalmologist if they suspect ocular toxoplasmosis. The specialists may prescribe medicine to treat active disease, depending on the size and severity of the eye lesion.

The majority of infants infected with toxoplasmosis in utero have no symptoms at birth but may develop symptoms later in life, with a small percentage of infected newborns incurring serious eye or brain damage at birth.

How cat ladies (and men) can avoid toxoplasmosis

Credit: Contributed by

Credit: Contributed by

If you want to avoid the slight risk of mental illness due to toxoplasmosis, start by taking safety precautions with your own cat, Torrey told Cats generally get the parasite from infected rodents or birds they hunt outside, or by coming into contact with the feces of an infected cat. "Cats kept exclusively indoors are quite safe," Torrey said. "For outdoor cats pregnant women should not change the litter box and children's sandboxes should be covered at all times when not in use." He also recommended using gloves when gardening in soil since cats also use the bathroom in the garden.

The CDC also recommends these safe food handling tips to prevent both toxoplasmosis transmitted via cat feces and the incidents that occur through raw meat and contaminated water or produce:

•Freeze meat for several days at sub-zero temperatures before cooking to greatly reduce chance of infection.
•Peel or thoroughly wash fruits and vegetables before eating.
•Do not eat raw or undercooked oysters, mussels, or clams. They may be contaminated with Toxoplasma that has washed into sea water.
•Do not drink unpasteurized goat's milk.
•Wash cutting boards, dishes, counters, utensils and your hands with hot, soapy water after contact with raw meat, poultry, seafood or unwashed fruits or vegetables.
•Wear gloves when gardening and during any contact with soil or sand because it might be contaminated with cat feces that contain Toxoplasma. Wash hands with soap and warm water after gardening or contact with soil or sand.
•Teach children the importance of washing hands to prevent infection.

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