Monkey Study Highlights Zika-Related Miscarriages

BETHESDA, Md. (CN) – Suggesting that human carriers of the Zika virus experience pregnancy loss more commonly than previously thought, researchers reported new findings Tuesday involving monkeys.

A crab-eating macaque and her juvenile at Djuanda Forest Park, West Java, Indonesia. (Image via Wikipedia)

Fifty Zika-infected macaques from six National Primate Research Centers across the United States were involved in the study, and researchers found that miscarriage or stillbirth occurred in 13 of them, about 26 percent.

All of the monkeys were infected with Zika in the laboratory, but those “infected early in pregnancy had significantly higher rates of fetal death than those infected after gestation day 55,” the National Institutes of Health said Tuesday in a press release.

Funding for the study, which appears in the journal Nature Medicine, came from its National Institute of Allergy and Infectious Diseases (NIAID) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), both divisions of the NIH.

Researchers say human data is on par with what they found in macaques: that women infected with Zika in their first trimester experience more severe fetal outcomes compared with those infected later in pregnancy.

This underscores the need for careful monitoring of fetal loss and stillbirth in Zika-affected human pregnancies.

Transmission electron microscope image of negative-stained, Fortaleza-strain Zika virus (red), isolated from a microcephaly case in Brazil. (Image via National Institute of Allergy and Infectious Diseases)

The Zika virus was first discovered in 1947, but the NIH notes that it was not until the Americas experienced a large Zika outbreak in 2015 that Zika-related birth defects were reported.

When an infected pregnant woman passes the Zika virus to her fetus, the child may suffer a range of birth defects collectively known as congenital Zika syndrome.

Adult humans infected with Zika meanwhile are commonly asymptomatic, but some will present with fever, rash, headache, joint pain, red eyes and muscle pain.

Treatments or vaccines for Zika virus remain in various stages of development. One such experimental vaccine being led by the NIAID is at Phase 2 of the trial stage.

The NIH press release also points to research recently published in the New England Journal of Medicine that shows “a 5.8 percent miscarriage rate and a 1.8 percent stillbirth rate in a cohort of pregnant women with symptomatic Zika virus infection in French Guiana, Guadalupe or Martinique.”

“Authors of the new nonhuman primate analysis note that the rates from the NEJM study could be an underestimate — the study included only symptomatic pregnant women, whereas many people with Zika infection are asymptomatic,” the press release continues.

While it can be transmitted sexually, the NIH notes that the most common method of Zika transmission among humans is the bite of an infected Aedes aegypti mosquito.

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