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When a cat eats an infected rodent, the parasite ends up in the cat’s poop, and humans can become infected if they accidentally ingest cat feces, though the infection typically only causes problems for those with suppressed immune systems and pregnant women (a small percentage of fetuses suffer birth defects due to maternal infection).
The only way to get the parasite is to consume toxoplasma gondii eggs, so you would have to ingest cat poop to get it from your cat, which is why most people become infected after eating undercooked meat or unwashed garden produce rather getting the infection from their pets.
How risky is toxoplasmosis to the fetus?
Women who are exposed to the parasite more than six months before becoming pregnant are unlikely to transmit the infection to their babies, and the majority of infected women fall into this category. Globally, up to 60% of all people carry the parasite, but their immune systems typically keep it under control so it doesn’t create any symptoms.
When infected during her first trimester, a mother has a 10%-15% chance of passing the parasite on to her child, and even if she does, problems are rare. However, there is some risk, so pregnant women should have someone else clean the litter box or clean it thoroughly a couple of times per day using gloves (the eggs take 1-5 days to mature and become infectious, according to the CDC).
How do humans get toxoplasmosis?
Although people tend to associate the Toxoplasma gondii parasite with cats, there are actually lots of other ways to get it. Common ways to become infected include:
- Eating undercooked meat that is infected with the parasite or touching your mouth during or after preparing meat if you haven’t washed your hands thoroughly.
- Eating other food that has been contaminated by utensils, cutting boards, or kitchen surfaces that have been in contact with raw contaminated meat.
- Drinking water contaminated with the parasite.
- Drinking contaminated raw goat’s milk.
- Eating unwashed contaminated garden produce.
- Ingesting cat feces by changing the litter box, not washing your hands afterwards, and putting your hand in your mouth, or touching unwashed surfaces where cats have pooped and then putting your hand in your mouth.
- Touching dogs, because they like to eat and roll in cat feces, so they may spread the infection to their owners when owners touch them and then touch their own mouths. Dogs may also become infected and excrete the parasitic eggs in their feces, and humans can become infected while handling dog feces that have been sitting around for a day or more or touching surfaces contaminated with dog poop and then touching their mouths.
Note: The parasite cannot be absorbed through the skin. You have to consume it orally. That’s why preparing and eating meat is a far more common cause of infection than changing the cat’s litter box.
Can toxoplasmosis change personality?
Some research suggests that the Toxoplasma gondii parasite may increase testosterone levels and could have slight personality effects on people. Men infected with toxoplasma gondii are more likely to be rule breakers, and to be more suspicious, jealous, expedient, vigilant, and dogmatic, and infected women tend to be more conscientious, warmhearted, persistent, moralistic, and outgoing. Infected people are also slightly more likely to be involved in traffic accidents. However, it is unknown whether the parasite causes personality and behaviour changes or those with certain characteristics are more likely to become infected. In other words, rebellious, high-testosterone men and warmhearted, friendly women may be more likely to eat undercooked meat and drive carelessly, leading to increased risk of both toxoplasmosis infection and car accidents. So, the parasite may cause minor personality changes, or certain types of people may be more likely to get infected, in which case, the parasite doesn’t affect human behaviour at all.
Disclaimer: This article is provided for informational purposes only, and is not intended as a substitute for medical advice. Medical concerns should be referred to a qualified doctor.
References
- Chaudhry, S. A., Gad, N., & Koren, G. (2014). Toxoplasmosis and pregnancy. Canadian Family Physician, 60(4), 334-336.
- Cunha, JP. DO, FACOEP, & Conrad Stoppler, M., MD (Editor)(2015). Toxoplasmosis (Toxo). Medicine.net.
- Dubey, J. P., MVSc, PhD. (2016). Overview of Toxoplasmosis. Merck Veterinary Manual.
- Flegr, J. (2007). Effects of Toxoplasma on human behavior. Schizophrenia Bulletin, 33(3), 757-760.
- Jenum, P. A., Stray-Pedersen, B., Melby, K. K., Kapperud, G., Whitelaw, A., Eskild, A., & Eng, J. (1998). Incidence of Toxoplasma gondii infection in 35,940 pregnant women in Norway and pregnancy outcome for infected women. Journal of Clinical Microbiology, 36(10), 2900-2906.
- Lopes, A. P., Granada, S., Oliveira, A. C., Brancal, H., Dubey, J. P., Cardoso, L., & Vilhena, H. (2014). Toxoplasmosis in dogs: first report of Toxoplasma gondii infection in any animal species in Angola. Pathogens and Global Health, 108(7), 344-346.