A recent study involving 601 senior citizens has uncovered a possible connection between higher antibody levels against Toxoplasma gondii, a parasite commonly associated with cats, and signs of frailty.
Symptoms of frailty can include fatigue, decreased muscle mass, and other indicators of health decline.
Toxoplasma gondii has previously been linked to various behaviors, such as risk-taking and certain mental health issues.
Research Overview
This research, led by a collaboration between teams from the University of Colorado Boulder, the University of Maryland School of Medicine, and the University of A Coruña in Spain, adds to the expanding evidence that this single-celled parasite may have significant implications for human health.
Christopher Lowry, a professor from CU Boulder’s Department of Integrative Physiology and one of the study’s co-authors, remarked that while T. gondii infections are often thought to be mild, there is growing concern they may pose serious health risks for some individuals as they age.
In the United States, it’s estimated that 11% to 15% of people have encountered T. gondii at some point in their lives, with even higher rates among older adults.
In certain countries, these infection rates can exceed 65%.
Once infected, people may harbor the parasite unknowingly, sometimes for their entire lives.
Link Between Antibodies and Frailty
The research team evaluated blood samples from 601 adults aged over 65 in Spain and Portugal, examining key frailty indicators like cognitive decline, fatigue, and unintentional weight loss.
Their analysis revealed that about 67% of participants tested positive for a latent T. gondii infection.
Interestingly, while they didn’t find a direct link between active infections and frailty, they saw that individuals with higher levels of antibodies tended to exhibit more pronounced frailty symptoms.
The authors of the study suggested that increased serointensity could signify a more severe infection, multiple infections, or a reactivation of a dormant infection that had intensified.
Implications and Future Research
Blanca Laffon, another co-author and professor at the University of A Coruña, highlighted the significance of this research.
It marks the first time a connection between immune response to T. gondii and frailty in older adults has been established.
T. gondii primarily lives and multiplies in the intestines of domestic and wild cats, with birds and rodents as secondary hosts.
Infected felines shed eggs into their feces, which can contaminate the environment and lead to human infection through contact with contaminated soil or the consumption of undercooked meat.
Remarkably, most infected individuals are unaware of their status, as only around 10% experience mild flu-like symptoms during the initial infection period.
The parasite can remain dormant for extended periods, forming cysts in muscles and brain tissues, particularly in areas linked to emotional processing, like the amygdala.
Research has suggested that T. gondii can alter host behavior in unique ways.
For instance, rodents infected with the parasite may lose their fear of cats, which assists felines in hunting.
Similarly, some infected chimpanzees have shown an unusual attraction to the scent of leopards, their natural predators.
In humans, the effects of T. gondii may be associated with increased tendencies toward impulsive behavior and higher rates of schizophrenia and mood disorders.
These connections have been explored in prior research conducted by Lowry and Dr. Teodor Postolache, a senior author of the current study.
While the authors did not establish a direct cause-and-effect relationship, they noted a significant correlation deserving of further investigation.
Their findings also revealed that frail individuals who had high levels of T. gondii antibodies showed elevated inflammatory markers.
This suggests that the infection could exacerbate age-related inflammation, often referred to as “inflammaging.”
Given that T. gondii can reside in muscle tissue, Postolache speculates that it might play a role in sarcopenia, the muscle mass loss associated with aging.
Lowry’s research explores how microorganisms influence immune responses and how this interaction affects mental health.
He pointed out that while many microbes co-evolved with humans and may have beneficial effects—described in the Old Friends hypothesis—some can pose risks under certain circumstances.
For T. gondii, situations like certain medications or conditions that weaken the immune system, such as HIV or cancer, can trigger dormant infections to reactivate, leading to negative health outcomes.
Lowry cautioned that even in individuals with robust immune systems, the aging process can lead to a decline in immune function, potentially allowing latent infections to awaken.
The researchers are hopeful that their findings will inspire more extensive studies into the relationship between T. gondii and frailty, possibly paving the way for strategies to mitigate the parasite’s harmful effects.
They also recommend that individuals at higher risk, particularly pregnant women and those with compromised immune systems, take precautions to prevent infection.
Source: ScienceDaily