Zika viral genome detected in the amniotic fluid of two fetuses with microcephaly

1. In this case study, Zika virus genome was detected and sequenced in the amniotic fluid of two pregnant women whose fetuses were found to have microcephaly.

2. Though transplacental transmission is necessary for fetal infection, the relationship between fetal microcephaly and Zika virus infection remains unclear.

Evidence Rating Level: 4 (Poor)

Study Rundown: An ongoing epidemic of Zika virus and the suspected link between intrauterine infection and microcephaly has focused attention on establishing transplacental transmission of Zika virus, as it is necessary for fetal infection. This case study aimed to identify and sequence the Zika virus genome in the amniotic fluid of two pregnant women in Brazil whose fetuses were diagnosed with microcephaly. The women presented with clinical manifestations that may have been of Zika virus at 18 weeks’ and 10 weeks’ gestation. Fluid attained via transabdominal amniocentesis was analyzed for the presence of Zika virus genome. Zika virus genome was detected and sequenced in the amniotic fluid of both women. Sequencing supported the Brazilian Zika virus genome is not a recombinant strain with other mosquito-born viruses in the same family. These results suggest that the Zika virus can move across the placental barrier and is a potential infectious agent for human fetuses. This study is the first to isolate the entire Zika virus directly from the amniotic fluid of pregnant women, providing evidence for transplacental transmission. However, these results must be verified with stronger levels of evidence in order to guide best practice recommendations. In addition, this study does not establish Zika virus as the causal agent for microcephaly.

The study was funded by Consellho Nacional de Desenvolvimento e Pesquisa (CNPq), Fundacao de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ).

Click to read the study in The Lancet Infectious Diseases

Relevant Reading: Zika virus associated with microcephaly

In-Depth [case study]: This is a case study in which quantitative reverse transcription polymerase chain reactions (RT-qPCR) and viral metagenomics were used to detect and sequence the genome of Zika virus from amniotic fluid of two women with fetuses found to have microcephaly. Two women who had experienced clinical manifestations which could have been symptoms of Zika virus (rash, myalgia, fever) at 18 and 10 weeks gestation, respectively, were included in this case study.

At 28 weeks’, amniotic fluid obtained via transabdominal amniocentesis was obtained from the women and analyzed by RT-qPCR and viral metagenomic next generation sequencing. Recombination events were assessed and phylogenetic reconstruction was performed by comparing the genome sequence of Brazilian Zika virus with other endemic flaviviruses. Zika virus genome was detected in the amniotic fluid of both women. Tests for chikungunya virus, Toxoplasma gondii, dengue virus, rubella virus, cytomegalovirus, herpes simplex virus, HIV, Treponema pallidum, and parvovirus B19 were negative.

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