A cat-borne parasite that infects about 40 million people in the United States may cause adults to be more frail as they age, according to a new University of Colorado Boulder study.
The parasite is already associated with risk-taking behavior and mental illness, according to a release, and the CU Boulder study found it may also contribute to signs of frailty including exhaustion and loss of muscle mass.
The parasite, called Toxoplasma gondii, affects about 11% of people in the United States, or roughly 40 million people, according to the Centers for Disease Control and Prevention. Rates tend to be higher in older people, and in some countries, more than 60% of people have been infected, according to the CDC.
“We often think of T. gondii infection as relatively asymptomatic, but this study highlights that for some people it may have significant health consequences later on,” Christopher Lowry, CU Boulder professor in the Department of Integrative Physiology, said in a release.
For the study, the team examined the blood of 601 Spanish and Portuguese adults older than 65 and looked at frailty, including unintentional weight loss, tiredness and loss of cognition.
About 67% of study subjects showed markers in their blood of a latent infection, or an infection by the parasite that was inactive in their body and showed no symptoms.
The researchers did not, as they hypothesized, find an association between an infection to T. gondii and frailty, according to the study. However, they did find that those with a higher concentration of antibodies to the parasite were significantly more likely to be frail.
A higher concentration of antibodies could reflect a more virulent or widespread infection, multiple infections or recent reactivation of a latent infection, the release said.
Wild and domestic cats are considered the definitive host of the parasite, while warm-blooded animals like birds and rodents are secondary hosts. When cats eat infected animals, T. gondii takes up residence and multiplies in their intestines, shedding eggs in their feces.
People are typically infected through exposure to litter boxes, contaminated water, dirty vegetables or by eating undercooked pork, lamb or other meat that’s infested.
Most people never know they’ve been infected and only about 10% initially have brief flu-like symptoms. Most healthy people recover from it without treatment, according to the CDC.
However, mounting research suggests that the parasite tends to linger dormant for decades, located in cysts in muscle and brain tissue with some serious impacts, the release said.
People who have been infected tend to engage in risky behavior, with research showing they tend to be more impulsive, more entrepreneurial and more likely to get in a car crash, the release said. They also have higher rates of schizophrenia, certain mood disorders, cognitive problems and are more likely to attempt suicide, according to research by Lowry and Teodor Postolache, a professor at University of Maryland School of Medicine and senior author on the new study.
The new study does not prove that T. gondii causes frailty, but it does identify a compelling association for further study.
Their research suggests that infection with the parasite could exacerbate inflammation that already occurs with aging. Because dormant T. gondii tends to hide out in muscle tissue, Postolache suspects it could also play a role in accelerating age-related muscle wasting.
“This paper is important because it provides, for the first time, evidence of the existence of a link between frailty in older adults and intensity of the response to T. gondii infection,” co-author Blanca Laffon, a professor at the University of A Coruña in Spain, said in the release.
For those infected with the parasite, certain medications or immune compromising diseases like HIV or cancer can enable a dormant infection to reactivate with adverse effects. Even in people with healthy immune systems, Lowry said in the release, immune function can decline with age, potentially enabling T. gondii to activate.
The researchers said in the release they hope their study will inspire more research into the relationship between T. gondii and frailty, and ultimately lead to new ways of keeping the parasite from doing harm.
For now, they encourage people — especially pregnant, elderly and immune compromised people— to take steps to avoid infection.
Prevention strategies improve changing the litter box daily and washing hands afterward, avoiding undercooked meat and rinsing fruits and vegetables. Keep cats indoors and avoid stray cats. If pregnant or immunocompromised, avoid changing the litter box if possible. Infection can cause serious problems during pregnancy to a developing fetus.
For those who may be infected, a health care provider can order blood tests specific for the parasite to determine whether there’s an infection and determine how recent it is.
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