Dangerous toxoplasmosis often causes long-term consequences in the brain

Toxoplasmosis affects memory in old age
Infection with Toxoplasma gondii can be dangerous especially for pregnant women. This could affect the health of newborns. But the dangerous pathogen apparently has a much longer-term impact. According to researchers, infection can also affect memory in old age.

Every second German carries pathogens in the body
More recently, US scientists have reported that some owners of cats have an increased likelihood of aggression and irascibility. For those who had been infected by Toxoplasma gondii. Every second German is the carrier of this pathogen. The world's single-celled organisms cause one of the most common infectious diseases, toxoplasmosis.

Toxoplasmosis can apparently affect working memory in old age. The pathogen, which is transmitted to humans through, among other things, cats, has so far been linked above all to dangers for pregnant women. (Image: M.Dörr & M.Frommherz / fotolia.com)

Especially dangerous for pregnant women and newborns
This disease is mainly associated with health risks for people with weakened immune systems and during pregnancy. If an expectant mother becomes infected, it can lead to permanent malformations and injuries in the child. Unfortunately, toxoplasmosis in neonates often remains undetected, experts from the Robert Koch Institute (RKI) reported in the journal "Scientific Reports". This can have a negative impact much later.

Impairment of working memory in old age
Studies at the Leibniz Institute for Work Research at the TU Dortmund University (IfADo) have now shown that an infection can also affect the working memory in old age. As the college reported in a recent report, the parasite Toxoplasma gondii propagates only in the gut of cats. About the cat feces, the robust parasite eggs find their way into foreign organisms, such as mice or birds.

Accordingly, humans often become infected by contaminated water, vegetables, or uncooked meat from infected livestock. Although the infection remains unnoticed in most cases, the gastric acid-resistant pathogens can cross the blood-brain barrier and live in nerve cells for life.

Deteriorated quality of life
The scientists at the IfADo have now for the first time investigated whether this affects cognitive abilities. In a double-blind study with seniors, they were able to show that a latent infection can worsen memory performance and subjective quality of life. They tested two groups of people over the age of 65, one half was latently infected with toxoplasmosis, the other was not. In the journal "Biological Psychology" they reported on their results.

Lower performance of working memory
All subjects had to answer questions about life situation and quality of life. This was followed by various PC tests on attention, memory, ability to concentrate and speed of information processing.

Participants should, inter alia, press a key in a fast succession of individual letters whenever the penultimate letter matches that currently shown. In this way, letters must be stored in short-term memory and continually compared to the new characters.

It was found that working memory performance was 35 percent lower in the toxoplasmosis-positive subjects than in the non-infected. In addition, the affected persons value their physical, mental and social quality of life significantly worse. The found deficits in the memory performance were objectified with EEG-based examinations.

Connection of toxoplasmosis and dementia
"The difference in working memory performance between infected and non-infected roughly equals the difference between healthy young adults and seniors," said IfADo study author Dr. Patrick Gajewski.

According to the experts, a toxoplasmosis infection-related imbalance in dopamine and norepinephrine neurotransmission is attributed to the effects. Therefore, in subsequent studies, a link between toxoplasmosis and dementia should be investigated, since in both cases memory function is the first to be affected. "The high prevalence of toxoplasmosis infection and a growing number of elderly people illustrates the socio-economic significance of the findings," said Gajewski. (Ad)