“This study in a nonhuman primate provides an important contribution to our understanding of the course of Zika virus infection in primates,” Amelia Pinto of Saint Louis University, Missouri, who was not involved in the work, said in a statement sent to reporters. However, “this study is ongoing, so from the results reported in this paper we cannot yet say that macaques are going to be a good model for understanding the links between Zika infection during pregnancy and the increased risk for microcephaly,” Pinto added.
In previous, unpublished work, O’Connor and colleagues infected two pregnant macaques with Zika during the animals’ third trimesters, sacrificed the fetuses at full term, and performed necropsies on them. The team did not observe evidence of microcephaly in the baby monkeys, but is still analyzing the aborted animals’ tissues. For the present study, the researchers infected pregnant monkeys during their first trimesters of pregnancy, as well as non-pregnant rhesus macaques (three males and three females).
With monkeys, “you can do experiments much more comprehensively than only with imaging in humans,” O’Connor said yesterday (June 27) during a press briefing.
The team detected the virus in the animals’ blood, urine, and saliva for up to 17 days post-injection. The virus was also found, for less than a week, in cerebrospinal fluid and vaginal fluid, the researchers wrote. None of the infected monkeys showed symptoms of Zika infection.
It’s unclear why the pregnant monkeys remained infected for longer than the non-pregnant ones. “Our leading hypothesis is it indicates the fetus is infected and is shedding virus back into mother’s bloodstream,” O’Connor told reporters during the briefing.