HMN 2025: How New online test detects toxoplasmosis without need for blood sample

An international research team has developed an easy online test capable of detecting toxoplasmosis infection without a blood sample, opening the door for a better understanding of how the common parasite affects human behavior.

Dr. Michele Garagnani from the University of Melbourne, Carlos Alós-Ferrer from Lancaster University and Anja Achtziger from Zeppelin University, developed the test, which assesses an individual’s reaction times to help determine whether they are infected with the protozoan parasite “Toxoplasma gondii,” which causes toxoplasmosis.

Until now, the only way of testing for infection was through a blood or saliva test.

“If you have an RhD negative blood type, an underlying toxoplasmosis infection will worsen your reaction times by less than a second and while this difference is barely noticeable, it is enough for us to assess whether you’re likely to be carrying the parasite,” Dr. Garagnani said.

Most commonly transmitted through cat feces or contaminated raw meat, the parasite affects around 30% of the global population.

Toxoplasmosis doesn’t pose an immediate risk for the average healthy person, and many may go through life without realizing they’re carrying it.

However, previous research suggests that for some people, toxoplasmosis infection can cause havoc with dopamine levels, reducing their self-control, making them more impulsive, impatient and more prone to risky decision-making.

“Toxoplasmosis affects our neurochemistry by influencing the regulation of neurotransmitters such as dopamine, serotonin, and adrenaline, which are also responsible for regulating behavior such as fear,” Dr. Garagnani said.

“When we estimate that toxoplasmosis affects 2.4 billion people worldwide, that’s a very large portion of the global economy who are having their decisions at least partially influenced by a parasite.”

To confirm the validity of the reaction test as a diagnostic tool, the research team conducted a head-to-head clinical trial comparing their proposed test against the conventional blood test.

Researchers measured the reaction times of 79 participants with an RhD-negative blood type and the results showed their new test had a 97% accuracy rate. The study is published in the journal Acta Psychologica.

“Our reaction test detected a toxoplasmosis infection in 11 out of the 12 participants who were identified as infected by the blood tests,” Dr. Garagnani said.

The research team then recruited an additional 1,010 individuals with an RhD-negative blood type and they too completed the online reaction times test.

Based on the results, the research team deemed 18% of the respondents to be infected with toxoplasmosis.

All the respondents were then asked a series of questions about their life including their employment status and yearly income.

“The survey findings revealed respondents who were deemed infected with toxoplasmosis were 10% more likely to be unemployed and earn less income on average than the respondents who were deemed to be non-infected,” Dr. Garagnani said.

“We also found that those who were deemed infected were more likely to smoke, drink alcohol and experience mental health problems such as anxiety, stress and depression compared to the non-infected participants.”

While this new online test doesn’t replace a medical diagnosis, it gives researchers an opportunity to properly measure the changes toxoplasmosis infection can have on the population.

“It isn’t practical or cost-effective to take enough blood samples to study behavioral effects of toxoplasmosis on a large scale,” Dr. Garagnani said.

“While there is no known treatment for toxoplasmosis, our new method is an opportunity for the world as a whole to understand how many of us are infected, how it affects our behavior, and what steps we can take to manage its impact.”