Zika infection after birth causes brain damage in monkeys

Complications from the Zika virus in babies born to women who were infected during pregnancy are well known. Now researchers working with monkeys say infections after birth could also result in brain abnormalities. 

When the World Health Organization (WHO) declared Zika a global health emergency in 2016, much of the concern centred on how the virus can result in severe birth defects — such as underdeveloped brains — when pregnant women were infected. The virus spreads mainly by mosquitoes but can also be sexually transmitted.

In Wednesday’s issue of the journal Science Translational Medicine, Dr. Ann Chahroudi of Emory University in Atlanta and her team say they found brain abnormalities during the first year of life in rhesus macaques that were infected with Zika after birth.

Dr. Angela Rocha shows brain scans of a baby born with microcephaly at the Oswaldo Cruz Hospital in Recife, Brazil, in 2016. New findings from monkeys suggest health authorities should closely monitor Zika infections in children and infants, and follow such cases over longer periods of time. (Felipe Dana/Associated Press)

“The neurological, behavioral and emotional differences remained months after the virus cleared from the blood of the infants,” Chahroudi, a pediatric infectious disease physician, said in a release.

“This is why our team now recommends more than just routine monitoring for pediatric patients known to be infected with Zika.”

To learn more, researchers infected six infant macaques with Zika five weeks after birth.  

After infection, the virus invaded the peripheral and central nervous systems, leading to abnormalities such as inflammation, an increase in astrocytes — a certain kind of star-shaped brain cell — and destruction of nearby neurons, as well as other damage.

The scientists also took MRI brain scans of the monkeys at three and six months of age to look for changes in anatomy and function in infected animals compared with two healthy, control animals.  

The scans pointed to changes in the brain’s limbic system, which is involved in regulating emotion.

The scans also helped to confirm which brain regions areas are damaged by the virus or are harmed indirectly by inflammation, the study’s authors said.

Infected monkeys also acted differently in behavioural stress tests compared with healthy monkeys, such as making abnormal calls when faced with a mild threat from a human intruder.  

The data suggest Zika infection after birth may disrupt how areas of the brain mature, which results in poor emotional processing, they said.

Only a small number of monkeys were used in the study and results of animal studies often don’t apply to humans. The U.S. National Institutes of Health recently funded a study of Guatemalan children infected with Zika after birth, the researchers said, which could shed more light for clinicians.

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