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West Nile and Powassan can spread from an infected pregnant mouse to her fetuses, causing brain damage and fetal death, according to a new study from Washington University School of Medicine in St. Louis. The findings suggest that Zika may not be unique in its ability to cause miscarriages and birth defects.
It is possible that viruses related to Zika, such as West Nile, pose the same risk to developing fetuses that Zika does. Researchers linked Zika infection in pregnant women with the risk of bearing babies born with microcephaly, or abnormally small heads.
Like Zika, both belong to the flavivirus family and target neural tissues. West Nile Virus (WNV) has the potential to cross the placenta and damage developing fetuses, according to new studies in mice. As part of the study and for comparison, Platt and Miner also wanted to study the effects of two mosquito-borne viruses only distantly related to Zika: chikungunya and Mayaro. Both are found in Brazil and can cause arthritis.
They injected female mice at day six of their pregnancies with one of the four viruses, then examined the placentas and fetuses a week later. All four viruses infected the placentas and fetuses, but levels of West Nile virus were 23- to 1,500-fold higher than those of the other three viruses in the placentas, and 3,000- to 16,000-fold higher in the heads of the fetal mice.
In addition, brain tissue from West Nile-infected fetuses showed severe damage under the microscope, while brain tissue from chikungunya-infected fetuses appeared healthy. They found that the three flaviviruses – Zika, West Nile and Powassan – multiplied in human placentas while chikungunya and Mayaro did not.
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