Common Cat Borne Parasite Found To Alter, Amplify Brain Disorders
How your cat is “driving” you crazy.
I have always warned people around me. Cats are going to be the end of us. Yeah, don’t listen but they are coming for us all. Now there’s new evidence pointing to the same.
Toxoplasma Gondii is a parasite that causes toxoplasmosis—the reason pregnant women are told to avoid cats’ litter boxes. T. gondii is also a major threat to people with weakened immunity. Healthy children and adults, however, usually experience nothing worse than brief flu-like symptoms before quickly fighting off the protozoan, which thereafter lies dormant inside brain cells—or at least that’s the standard medical wisdom.
Now, a new discovery by 32 scientists at 16 institutions, throws light on how we have severely underestimated the situation. The researchers analyzed genetic, transcriptomic, and proteomic data from infected individuals, and from studies in cell cultures, to link T. gondii infection with a number of brain disorders, including epilepsy, Alzheimer’s and Parkinson’s diseases, and even some cancers.
“This study is a paradigm shifter,” stated co-author Dennis Steindler, Ph.D., director of the Neuroscience and Aging Lab at the Jean Mayer USDA Human Nutrition Research Center on Aging
at Tufts University. “We now have to insert infectious disease into the equation of neurodegenerative diseases, epilepsy, and neural cancers. At the same time, we have to translate aspects of this study into preventive treatments that include everything from drugs to diet to lifestyle, in order to delay disease onset and progression.”“We wanted to understand how this parasite, which lives in the brain, might contribute to and shed light on pathogenesis of brain diseases,” said Rima McLeod, M.D., professor of ophthalmology & visual science and pediatrics and medical director of the Toxoplasmosis Center at the University of Chicago. “We suspect it involves multiple factors. At the core is alignment of characteristics of the parasite itself, the genes it expresses in the infected brain, susceptibility genes that could limit the host’s ability to prevent infection, and genes that control susceptibility to other diseases present in the human host. Other factors may include pregnancy, stress, additional infections, and a deficient microbiome. We hypothesized that when there is confluence of these factors, disease may occur.”
The team focussed on the human “infectome” plausible links between the parasites’ secreted proteins, expressed human microRNAs, the neural chemistry of the human host, and the multiple pathways that are perturbed by host-parasite interactions.
Using the data collected from the National Collaborative Chicago-base congenital Toxoplasmosis Study, which has diagnosed, treated and followed 246 congenitally infected people and their families since 1981, they performed a “comprehensive system analysis”, looking at a range of parasite-generated biomarkers and assessing their probable impact. They looked at the effect of infections of primary neural stem cells from the human brain in tissue culture, focussing on gene expression and proteins perturbed. Later, using “reconstruction and deconvolution” approach, were able to identify pathways associated with neurodegenerative diseases, brain disorders as well as some cancers.
Some estimates reckon that half the world’s population will be infected with T Gondii eventually, so more research into the parasite’s side effects is certainly welcome. A severely infected cat can excrete as many as 500 million parasite-carrying oocysts, and just one of those is infectious – even if it’s been left in soil or water for a year.
Therefore, this study doesn’t mean that, if you’re infected with T. gondii, that you’re at risk of contracting these diseases, or that an infection will exacerbate a pre-existing neurological condition. Because the parasite is altering genetic, proteomic and other brain factors, everyone is going to react differently. More work needs to be done to suss this out, and determine who is and who isn’t at risk.
“Our results provide insights into mechanisms whereby this parasite could cause these associated diseases under some circumstances,” the authors wrote. “This work provides a systems roadmap to design medicines and vaccines to repair and prevent neuropathologic effects of T. gondii infection of the human brain. Furthermore, our original template provides a novel method to integrate multiple levels of intrinsic and extrinsic factors highlighting a way to unravel complexity in brain parasitism, toxoplasmosis specifically, and other complex diseases.”
