On February 1, 2016, the World Health Organization declared the Zika virus to be a global health emergency. Spread by the bite of an infected mosquito, the Zika virus has moved rapidly across the Western hemisphere and is linked to potential birth defects.

A team of researchers at the University of Wisconsin-Madison, along with collaborators at Duke University and the University of California, Davis, is working to understand the threat Zika could cause to human pregnancies. Through their work with rhesus monkeys at the Wisconsin National Primate Research Center (WiNPRC), the researchers can uniquely understand the virus’ short and long-term effects.

“There are so many things about Zika infection we can’t study as well in pregnant humans – or fast enough to make a difference for a lot of people who may be infected,” says Dr. Dawn Dudley, a UW-Madison pathology research scientist. “The precise pathway that the virus takes from mom’s bloodstream to the fetal bloodstream, across that interface, cannot be studied except in an animal model.”

The research team, led by primate center scientist Dr. David O’Connor, monitored four pregnant rhesus macaque monkeys that were exposed to the Zika virus. Through regular assessment of maternal infection and fetal development, the researchers found evidence that the virus was passed efficiently to each fetus.

The infection spread inflammatory damage through the tissues that supported the fetus and its developing nervous system, suggesting that the virus poses a larger threat to human fetuses than originally theorized. In fact, three of the fetuses had small heads (although not quite small enough to diagnose microcephaly) and unusual inflammation of the eyes. However, the medical study did not find abnormal brain development.

These sobering results suggest that, as they grow, human babies who were exposed to the virus may develop more Zika-related disease pathology. Research teams are currently working to understand how Zika interacts with other infections, how the effects of early pregnancy infection differ from later infection, and whether antiviral therapies could manage the effects of congenital Zika syndrome.

Reviewed August 2019

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Photo credit: Wisconsin National Primate Research Center