Studies Prove That This Parasite Can Affect Human Social Behaviour

The single-celled parasite Toxoplasma gondii can infect our pet cats and is easily transmitted to us. Why should we care? Jaroslav Flegr of Prague’s Charles University (seen the the clip below) has linked toxoplasma infections in humans with increased traffic accident rates and personalit y changes. 

That raises a lot of questions, so help, we compiled answers from the British Columbia Centre for Disease Control, Manitoba Public Health and the United States Centers for Disease Control and Prevention.


Manitoba Public Health says: "Most people who are infected do not show any symptoms. Those who do get sick with a mild form of the illness will usually have flu-like symptoms including fever, sore throat, sore muscles, tiredness and swollen lymph nodes. In some cases, the infection can also cause vision problems. Immunocompromised people, such as those living with AIDS or cancer, or transplant patients receiving immunosuppressive drugs, and pregnant women are more at risk of serious illness."


US Centres for Disease Control and Protection says: "If you suspect that you may have toxoplasmosis, talk to your health care provider. Your provider may order one or more varieties of blood tests specific for toxoplasmosis. The results from the different tests can help your provider determine if you have a Toxoplasma gondii infection and whether it is a recent (acute) infection."


BC Centre for Disease Control says: "All animals and birds can be infected with the toxoplasmosis parasite. The parasite enters the muscles of a bird or animal when it eats raw meat or drinks the milk of another animal that is infected. Cats can also spread the parasite in their feces. Humans can become infected with toxoplasmosis when changing a cat litter box or working in an area contaminated with cat feces. 

Common ways for people to become infected with toxoplasmosis include:  eating raw or undercooked meats, drinking unpasteurized milk, cleaning cat litter boxes, working in gardens or playing in sandboxes that contain cat feces.

Less common ways for people to become infected with toxoplasma include: drinking water contaminated with toxoplasma,  although extremely rare, by receiving an infected organ transplant or blood transfusion."


The US Centres for Disease Control says: "Most healthy people recover from toxoplasmosis without treatment. Persons who are ill can be treated with a combination of drugs such as pyrimethamine and sulfadiazine, plus folinic acid."


Manitoba Public Health says: "Toxoplasmosis is easily prevented by practicing good hand hygiene, following good food safety practices and by wearing gloves when working in the garden or cleaning cat litter pans. Pregnant women should avoid cleaning cat litter pans."

The following list is from the BC Centre for Disease Control: 

  • order or cook your meat well done
  • do not eat raw or undercooked meat
  • wash your hands, utensils, and cutting boards after handling raw meat to prevent contamination of other foods
  • do not drink unpasteurized milk from any animal
  • be careful not to accidentally swallow dust when cleaning the cat litter box; clean the litter box daily so that the parasite does not have a chance to become infectious
  • avoid cleaning cat litter boxes if you are pregnant or trying to become pregnant
  • wear gloves when cleaning the cat litter box, then wash your hands
  • place a secure lid on your sandbox to prevent cats from using it as a litter box
  • wear gloves when gardening, then wash your hands
  • persons who are pregnant or have a weak immune system due to AIDS, cancer or following organ transplants and who are concerned about the quality of the water in their community should consult with their doctor about whether they should be treating their drinking water or using bottled water

BC Centre for Disease Control says: "A growing fetus can become infected with the toxoplasmosis parasite. This can happen if the mother is infected with the parasite while pregnant or slightly before she becomes pregnant. Infection in the unborn child early in pregnancy can result in miscarriage, poor growth, early delivery or stillbirth. If a child is born with toxoplasmosis, he/she can experience eye problems, hydrocephalus (water on the brain), convulsions or mental disabilities.

Treatment of an infected pregnant woman may prevent or lessen the disease in her unborn child. Treatment of an infected infant will also lessen the severity of the disease as the child grows."


The BC Centre for Disease Control says: "Just like other family members, your pet cat can pass the disease on to you. Most cats which are infected do not appear sick. The cat's feces contain the parasite for only two weeks after the cat is infected. However, the feces themselves may remain infectious for well over a year.

Cats which have been raised indoors, have never caught and eaten mice or birds, and who have never been fed raw meat are not likely to be infected. A stray or unfamiliar cat which appears sick should not be handled but should be reported to the SPCA or the pound."


The US Centers for Disease Control and Prevention says: "Yes, you may keep your cat if you are a person at risk for severe infection (e.g., you have a weakened immune system or are pregnant); however, there are several safety precautions to avoid being exposed to Toxoplasma gondii ."

  • Ensure the cat litter box is changed daily. The Toxoplasma parasite does not become infectious until 1 to 5 days after it is shed in a cat's feces.
  • If you are pregnant or immunocompromised:
  • Avoid changing cat litter if possible. If no one else can perform the task, wear disposable gloves and wash your hands with soap and warm water afterwards.
  • Keep cats indoors.
  • Do not adopt or handle stray cats, especially kittens. Do not get a new cat while you are pregnant.
  • Feed cats only canned or dried commercial food or well-cooked table food, not raw or undercooked meats.
  • Keep your outdoor sandboxes covered.
  • Your veterinarian can answer any other questions you may have regarding your cat and risk for toxoplasmosis.

Scientist Kevin Lafferty:

"I was intrigued by studies coming out that showed that people that were infected with toxoplasma had different personalities than people that were not infected. And men and women varied in their responses, but one of the consistent differences was that infected people tend to be more neurotic on average than uninfected people.

Neuroticism is associated with certain cultural dimensions. A good example is risk aversion. More neurotic populations tend to be more risk-averse, and they establish political and social structures that are more authoritarian, for instance.

Another example is gender differentiation. So in more neurotic cultures, there are stronger gender roles. Men do certain things, women do certain things. In less neurotic cultures, men and women do similar things.

The aspects of changes in personality, in culture, those are pretty subtle things. As an individual infected, it’s not something that you would be concerned about."


Manitoba Public Health
US Centers for Disease Control and Prevention
BC Centre for Disease Control
Can the common brain parasite, Toxoplasma gondii, influence human culture?
Toxoplasmosis snapshots: Global status of Toxoplasma gondii seroprevalence and implications for pregnancy and congenital toxoplasmosis

Available on CBC Gem

Invasion of the Brain Snatchers

Nature of Things