Researchers found Zika virus sequences in placenta and cord blood in newborns, supporting prior evidence of vertical transmission of Zika virus during pregnancy, according to data published in JAMA Neurology. However, the investigators did not observe changes in umbilical and cerebral blood flow.
Previous studies have reported an increase of microcephaly cases in fetuses whose mothers were infected with Zika virus. Amilcar Tanuri, MD, PhD, from the Federal University of Rio de Janeiro, and colleagues sought to examine the prenatal evolution and perinatal outcomes in 11 neonates with neurologic damage associated with Zika virus infection.
The researchers observed the infants from gestation to 6 months in Paraiba, Brazil. Seven infants were female, and the median maternal age at delivery was 25 years. Ten of the 11 women included in the study presented with symptoms of Zika during the first half of pregnancy, but all 11 women had Zika infection confirmed in several tissues by serology or polymerase chain reaction.
The investigators used intrauterine ultrasonography and magnetic resonance imaging to confirm brain damage, and they performed histopathologic analysis on placenta and brain tissue in infants who died. They also investigated the Zika virus genome in several tissues and performed genome sequencing for phylogenetic analysis.
The perinatal mortality rate was 27.3%. The median cephalic perimeter at birth was 31 cm, which was lower than the limit to consider a microcephaly case. The researchers observed neurologic impairments in all patients, including microcephaly, a reduction in cerebral volume, ventriculomegaly, cerebellar hypoplasia, lissencephaly with hydrocephalus, and fetal akinesia deformation sequence.
The Zika virus genome was identified in both maternal and neonatal tissues, including amniotic fluid, cord blood, placenta, and brain tissue. In addition, phylogenetic analyses revealed an intrahost variation between Zika virus sequences of some postmortem tissues.
The researchers concluded that amniotic fluid may be valuable for prenatal diagnosis of Zika virus. They did not note changes in umbilical and cerebral blood flow, and they also note that microcephaly could be a consequence of several brain injuries.
“Based on confirmed [Zika virus] ZIKV-associated cases of microcephaly reported by the Brazilian Ministry of Health, the northeastern region of Brazil has a 10 times larger incidence of confirmed cases compared with the rest of Brazil as well other Latin American countries where ZIKV circulates,” the study authors noted. “This fact suggests that there must be some additional unknown factor to enhance ZIKV fetal infection in this region. Coinfections as well as environmental factors should be explored to clear this unexpected finding.”
- Suely de Oliveira Melo A, Aguiar RS, Amorim MMR, et al. Congenital Zika virus infection: Beyond neonatal microcephaly. JAMA Neurol. 2016; doi: 10.1001/jamaneurol.2016.3720.