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How a parasite encourages us to love cats

How a parasite encourages us to love cats

Posted by Armarkat on 5th Jan 2024

You may have heard rumors about cats’ ability to “mind control” other creatures into adoring them. But how does that happen and why are we so susceptible to their influence? The answer may be a parasite called Toxoplasma gondii.

A largely harmless pathogen for most animals and humans, Toxoplasma gondii is most known for its ability to make felines’ prey less apprehensive around them. This cat-favoring trait increases a cat’s chances of catching its quarry.

According to the Guardian, “Rodents infected with the parasite Toxoplasma gondii, which reproduces in the gut of cats, lose their fear of cats. Even after an infection is cleared, their brain has been permanently rewired, which obviously doesn’t bode well for that particular rat or mouse.” The parasite accomplishes this change in outlook while increasing the output of dopamine, a neurotransmitter known for boosting positive emotions.

Many kinds of felines can spread Toxoplasma gondii, including but not limited to ocelots, bobcats, and Bengal tigers. Interestingly, domestic cats are the feline that most commonly contains the parasite, according to research in the Journal of Medical Microbiology.

Animals often become infected by Toxoplasma gondii after close contact with infected rodents or from eating cat feces. However, the spread of the parasite to humans usually takes place without any direct involvement from mice or cats. According to the Guardian, human infection is more “likely to have come from raw and undercooked meat and unwashed vegetables than from cats.”

Additionally, research reveals that a remarkable portion of the human population has been infected by Toxoplasma gondii. Findings published in the Journal of Medical Microbiology reported that “Approximately half a billion humans” have Toxoplasma gondii. The Centers of Disease Control and Prevention (CDC) estimates that as many as 40 million infected humans are living in the United States.

Some countries have compiled statistics on how common Toxoplasma gondii infections are projected to be in their human populations. Data from the Companion Animal Parasite Council estimates that Toxoplasma gondii is present in 11% of US residents aged between 6 and forty-nine. Comparatively, the parasite exists in roughly 20% of the human population in Brazil as well as 40% of the residents in Turkey. These statistics happen to correlate with data from A-Z Animals showing that as of 2017, the United States had the most cats of any country in the world and Brazil had the world’s third-largest cat population.

Turkey has a far smaller human population than either the US or Brazil, but that does not mean that cats have less influence there. According to The Travel, Turkey’s largest city Istanbul is “a haven for cat lovers,” as it is home to over 100,000 community cats, which are well cared for. Some Istanbul residents believe that there may be as many as one million cats in their city.

We’ve described the ‘charming’ effects Toxoplasma gondii has on those infected with it, but there are cautions to consider with this pathogen. According to the CDC, “Most people who become infected with Toxoplasma gondii are not aware of it because they have no symptoms at all.” However, ‘most’ certainly does not mean ‘everyone.’ Studies published in the Journal of Medical Microbiology state that those at risk of symptoms from a Toxoplasma gondii infection are children whose mothers acquired Toxoplasma gondii during pregnancy, as well as individuals who have immune system complications.

The CDC describes symptoms of those who are adversely affected by Toxoplasma gondii: “Some people who have toxoplasmosis may feel as if they have the “flu” with swollen lymph glands or muscle aches and pains that may last for a month or more. Severe toxoplasmosis, causing damage to the brain, eyes, or other organs, can develop from an acute Toxoplasma infection.” If you are pregnant or have a weakened immune system and suspect you have been infected with Toxoplasma gondii, see your doctor immediately to get tested. Fortunately, Toxoplasma gondii-positive patients can receive medication to eradicate the parasite and the symptoms. The CDC advises that pregnant women and individuals with conditions affecting their immune systems can keep their cats, but they should not adopt another cat while in that state. For both categories, the CDC also cautions that they have someone else change their cat’s litter box and that they ought to keep their cats indoors only.

It’s possible that all cat lovers have a parasite that increases or even causes their fascination with cats, but that doesn’t stop us from happily spoiling our feline pets! No matter the cause of our obsession with cats, we love them the same as always.

Quote to remember: “My house would be cleaner without my cat but my heart would be sad and empty!” - Martha Curtis


A-Z Animals, “Discover the Top 6 Countries With the Most Pet Cats”

Centers for Disease Control and Prevention (CDC), “Toxoplasmosis: General FAQs”

Companion Animal Parasite Council (CAPC), “Toxoplasma gondii”

National Library of Medicine, Medical Microbiology. 4th edition., Chapter 84, “Toxoplasma Gondii”

The Guardian, “Whisker fatigue and mind control: 19 amazing facts every cat-lover needs to know”

The Travel, “The City That Loves Cats: Why Is Istanbul A Feline Paradise?”