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  More evidence that Zika virus causes birth defects

More evidence that Zika virus causes birth defects

Published : Jun 30, 2016, 6:47 am IST
Updated : Jun 30, 2016, 6:47 am IST

New research, published on Wednesday in he Lancet, further provides evidence that Zika virus infection in the first trimester of pregnancy can result in placental and foetal damage.

New research, published on Wednesday in he Lancet, further provides evidence that Zika virus infection in the first trimester of pregnancy can result in placental and foetal damage.

Experts said that the Zika virus was detected in the brain tissue of a deceased two-month-old baby in Brazil who was diagnosed with microcephaly, in the brain tissue of two newborns who died shortly after birth and in the placenta tissue of two foetuses that were spontaneously aborted.

They said further studies to understand the exact mechanism of transmission are needed.

Since the start of the Zika outbreak in Brazil in March 2015, there have been 7,343 cases reported cases of microcephaly, of which 1,271 have been confirmed. Fifty-seven of the microcephaly cases were fatal.

During their study, Dr Sherif R. Zaki from the Division of High Consequence Pathogens and Pathology (DHCPP), Centres for Disease Control and Prevention, Atlanta, USA, and colleagues, analysed tissues from three post-mortem cases and two placentas. All five mothers reported symptoms of Zika virus infection during the first trimester of pregnancy. In three cases (two newborns who died within hours of being born, and one who died at two months), microcephaly was detected during pregnancy or at birth. The two other cases were foetuses spontaneously aborted at 11 and 13 weeks gestation. In the three fatal cases, Zika antigens were detected in the neurons and glial cells.

Analysis of brain tissue showed damage and degeneration of cells, microcalcification (calcium deposits), and cell death. The authors say that the absence of a substantial inflammatory response in the brain and any specific structural effects appear to distinguish Zika virus infection from other infections, such as herpes, that are associated with microcephaly.

No evidence of Zika virus was detected outside the central nervous system in the heart, liver, spleen, kidney or cartilage. All three cases showed a range of birth defects, including craniofacial malformations and a range of brain abnormalities.

Zika virus antigens were also detected in the placental tissue of the two aborted cases. Tests on all five cases were negative for the presence of dengue virus antibodies and tested negative for other infections including rubella virus, Toxoplasma gondii, and herpes. Genetic analysis of the Zika virus samples showed the greatest match to strains isolated in Brazil during 2015.

The authors say that the mechanism by which Zika virus may cause abnormalities is not yet understood, but that it’s likely the result of the virus attacking the nervous system with subsequent damage to the brain and muscle impairment.

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