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Suicide risk could be heightened by common cat and foodborne parasite

Kathleen Blanchard's picture
Parasite found in cat feces, meat and vegetables could raise suicide risk.

There’s no question that pet ownership is generally considered good for health and well-being, but a new study shows owning a cat, eating undercooked meat or not washing your vegetables thoroughly could put women at risk for a parasitic infection that is newly linked to increased risk of violent suicide attempts.

Toxoplasma gondii (T. gondii) infection associated with suicide attempts

In the new study, Denmark scientists found a direct association between infection with the toxoplasmosis – a parasite that could affect the brain – and suicide attempts later in life.

The parasite comes from cat feces, uncooked or undercooked meat, and can be transmitted by eating unwashed contaminated vegetables.

The study, published in the Archives of General Psychiatry, doesn’t prove the parasite leads to suicide attempts, but should at least serve as a warning to women who own cats that the link does exist.

Teodor T. Postolache, M.D, senior author and an associate professor of psychiatry and director of the Mood and Anxiety Program at the University of Maryland School of Medicine said in a press release, "We can't say with certainty that T. gondii caused the women to try to kill themselves, but we did find a predictive association between the infection and suicide attempts later in life that warrants additional studies. We plan to continue our research into this possible connection.”

The study authors say the parasite is common around the world and many people don’t even realize they’re infected because the parasite ‘hides’ in cysts inside the cells to escape attack from the immune system. The organism spreads to muscles and the brain of cats and other warm blooded animals. In people, toxoplasmosis might not cause symptoms, but is especially dangerous for pregnant women and anyone with compromised immune function.

Symptoms that are apparent include swollen lymph nodes and feeling like you have an extended case of the flu. Severe cases cause brain damage, which might explain the higher risk of suicide. Past studies have linked toxoplasmosis to schizophrenia and changes in behavior.

A blood test can help your doctor diagnosis whether you’ve been exposed to the disease. Treatment option are available, but should be discussed with your doctor. Prevention includes good hand and kitchen hygiene in addition to washing your fruits and vegetables and cooking your meat thoroughly. If you're pregnant, let someone else change the cat litter.

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Even in cats, toxoplasmosis is unlikely to cause problems. If your cat has symptoms of an illness that might be from the parasite, your veterinarian will perform testing. Treatment is with the antibiotic Clindamycin, according to Cornell University College of Veterinary Medicine.

According to the CDC, more than 60 million men women and children harbor the Toxoplasma parasite that can come from cleaning a cat litter box. The parasite thrives in cat’s intestines and when women handle cat feces, the organism could be transmitted hand to mouth. The same applies to eating vegetables or undercooked meat. The parasite can’t enter through skin that is intact, but a sore or cut on the hand or fingers could provide an entry point. Kitchen utensils can also be a source of infection.

Does toxoplasmosis really up suicide risk?

For the current study, researchers looked at 45,788 women in Denmark who gave birth between May 15, 1992 and January 15, 1995 whose babies were tested for the presence of T. gondii immunoglobulin G (IgG) antibodies. Since babies can’t produce antibodies until they’re 3-months old, a positive test mean their mothers’ had the infection.

The researchers then scanned medical records to find any association between suicide attempts with guns, sharp objects or jumping from high places among the women whose babies had the toxoplasmosis antibodies.

The results showed women were 1.5 times more likely to try to kill themselves if they had the parasitic infection, compared to women not infected. Higher antibody titer was linked to greater suicide risk; especially violent attempts. Previous history of mental illness did not alter the findings.

Postolache emphasizes that the study doesn’t prove Toxoplasma gondii and suicide are connected, but it does warrant further investigation. The researchers aren’t sure if the infection heightens the risk of suicide or if suicidal behaviors make people more vulnerable to the parasite.

"Is the suicide attempt a direct effect of the parasite on the function of the brain or an exaggerated immune response induced by the parasite affecting the brain? We do not know. In fact, we have not excluded reverse causality as there might be risk factors for suicidal behavior that also make people more susceptible to infection with T. gondii," Dr. Postolache says.

J. John Mann, M.D., of Columbia University, an international expert on suicide points out there is accumulating evidence that immune factors are associated with suicidal behavior. If future studies show toxoplasmosis does pose dangers to mental health and raises suicide risk in women (or men), new interventions can be developed for prevention. If you own a cat - and this author thinks you should consider pet ownership as a mean to better heath - just be aware that good hand washing technique is important after handling litter box contents. It's not just your cat litter box that can be a source of toxoplasmosis, which is also an important note.

Archives of General Psychiatry
"Toxoplasma gondii Infection and Self-directed Violence in Mothers"
Marianne G. Pedersen, MSc; Preben Bo Mortensen, DrMedSc; Bent Norgaard-Pedersen, DrMedSc; Teodor T. Postolache, MD
July, 2012