Seniors Calling. Zika Virus and the Aging Brain

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As the state of Florida, and other favourite wintering grounds in the United States of America continue to battle the Zika Virus, there are some things that Canadian Snowbirds may want to consider. And it is all about the brain.

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A recent medical study has found that Zika infection may affect adult brain cells, suggesting that the risk may not be limited to pregnant women. Mounting evidence suggests that Zika (ZIKV) infection in pregnant women can cause brain and congenital abnormalities in developing fetuses, including microcephaly, as well as spontaneous abortions.

However, new research in mice from scientists at The Rockefeller University and La Jolla Institute for Allergy and Immunology suggests that certain adult brain cells may be vulnerable to infection as well. Among these are populations of cells that serve to replace lost or damaged neurons throughout adulthood, and are also thought to be critical to learning and memory.

The research was published August 18,2016, in Cell Stem Cell.

“This is the first study looking at the effect of Zika infection on the adult brain,” says Joseph Gleeson, adjunct professor at Rockefeller, head of the Laboratory of Pediatric Brain Disease, and Howard Hughes Medical Institute investigator. “Based on our findings, getting infected with Zika as an adult may not be as innocuous as people think.”

Although more research is needed to determine if this damage has long-term biological implications or the potential to affect behavior, the findings suggest the possibility that the Zika virus, which has become widespread in Central and South America over the past eight months, may be more harmful than previously believed. The new findings were published in Cell Stem Cell on August 18.

 Zika Virus risk by State: The states at greatest risk are those along the Gulf Coast - Texas, Louisiana, Mississippi, Alabama and Florida (dark red). Meanwhile other Southern states, where mosquitoes are typically a problem could also see cases. But, with travelers returning from affected regions it is impossible to declare any state safe from the virus. (CDC)
Zika Virus risk by State: The states at greatest risk are those along the Gulf Coast – Texas, Louisiana, Mississippi, Alabama and Florida (dark red). Meanwhile other Southern states, where mosquitoes are typically a problem could also see cases. But, with travelers returning from affected regions it is impossible to declare any state safe from the virus. (CDC)

“Zika can clearly enter the brain of adults and can wreak havoc,” says Sujan Shresta, a professor at the La Jolla Institute of Allergy and Immunology. “But it’s a complex disease—it’s catastrophic for early brain development, yet the majority of adults who are infected with Zika rarely show detectable symptoms. Its effect on the adult brain may be more subtle, and now we know what to look for.”

ZikamosquitoEarly in gestation, before our brains have developed into a complex organ with specialized zones, they are comprised entirely of neural progenitor cells. With the capability to replenish the brain’s neurons throughout its lifetime, these are the stem cells of the brain. In healthy individuals, neural progenitor cells eventually become fully formed neurons, and it is thought that at some point along this progression they become resistant to Zika, explaining why adults appear less susceptible to the disease.

But current evidence suggests that Zika targets neural progenitor cells, leading to loss of these cells and to reduced brain volume. This closely mirrors what is seen in microcephaly, a developmental condition linked to Zika infection in developing fetuses that results in a smaller-than-normal head and a wide variety of developmental disabilities.

The mature brain retains niches of these neural progenitor cells that appear to be especially impacted by Zika. These niches—in mice they exist primarily in two regions, the subventricular zone of the anterior forebrain and the subgranular zone of the hippocampus—are vital for learning and memory.

The researchers found that infection correlated with evidence of cell death and reduced generation of new neurons in these regions. Integration of new neurons into learning and memory circuits is crucial for neuroplasticity, which allows the brain to change over time. Deficits in this process are associated with cognitive decline and neuropathological conditions, such as depression and Alzheimer’s disease.

The study suggests that some people, such as those with weakened immune systems, may be vulnerable to the virus in a way that has not yet been recognized.

“The virus seems to be traveling quite a bit as people move around the world,” says Gleeson. “Given this study, I think the public health enterprise should consider monitoring for Zika infections in all groups, not just pregnant women.”

Zika virus was first described in 1947 in Uganda, but has since spread to other parts of the world, with outbreaks occurring in the Western Hemisphere for the first time in 2014.

The entire study can be found here: (http://www.cell.com)

On The Zika Virus front, The Government of Canada, states, ‘As of August 25, 2016,  232 travel-related cases, 2 sexually transmitted cases and 3 reports of maternal-to-fetal transmission have been detected in Canada. There’s ongoing low risk to Canadians travelling to countries with mosquito-borne Zika virus infection.’ (http://www.healthycanadians.gc.ca)

According to the Centers For Disease Control and Prevention,   the Zika virus is mostly spread by a bite from an infected mosquito (of the Aedes species). These mosquitos are daytime biters, however they can still bite at night. You can also get Zika through sexual intercourse. www.cdc.gov/zika/)

Currently, there is no vaccine or medication for Zika.