Common parasite on cats may contribute to frailty in older people

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A new study, published in the Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, reveals a potential connection between the common cat-borne parasite Toxoplasma gondii (T. gondii) and frailty in older adults.

This international research, involving scientists from the University of Colorado Boulder and elsewhere, sheds light on the possible health consequences of T. gondii infection, which was previously considered relatively asymptomatic in humans.

Approximately 11% to 15% of people in the U.S. have been infected with T. gondii, with higher rates in older individuals.

The study focused on 601 Spanish and Portuguese adults over the age of 65, examining their blood samples and assessing markers of frailty, including unintentional weight loss, fatigue, cognitive decline, and other signs of declining health.

Of the participants, 67% were found to be “seropositive,” indicating that they had markers in their blood suggestive of a latent T. gondii infection.

While the study did not establish a direct link between T. gondii infection and frailty, it did reveal that among those infected, individuals with higher “serointensity” (higher concentrations of antibodies to the parasite) were more likely to be frail.

Higher serointensity may indicate a more severe or widespread infection, multiple infections, or recent reactivation of a latent infection.

The research highlights that T. gondii infection may have significant health consequences, particularly in older adults, challenging the assumption of its asymptomatic nature.

The findings suggest that latent T. gondii infections could exacerbate inflammation associated with aging, contributing to a condition known as “inflammaging.”

The study does not confirm a causal relationship between T. gondii and frailty but emphasizes the need for further research in this area.

The authors also suggest that T. gondii may play a role in age-related muscle wasting (sarcopenia), as the parasite tends to hide in muscle tissue.


This study provides valuable insights into the potential impact of T. gondii infection on the health of older adults, particularly in relation to frailty and inflammation.

While further research is needed to establish a causal link, the findings underscore the importance of understanding the complex interactions between microorganisms and the human immune system.

The study also highlights the importance of preventive measures to avoid T. gondii infection, especially for pregnant women, elderly individuals, and those with compromised immune systems.

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The research findings can be found in the Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences.

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