Monday, May 22, 2017

Zika virus, placental entry, and feijoada

In Uganda in 1947, Zika virus was first isolated. Zika occurs in many far-flung parts of the world. Just a few years ago, Zika arrived in Brazil (, and it was soon realized that Zika was associated with and likely causing microcephaly and other fetal malformations. (,

Why did it take until Zika arrived in Brazil for the Zika-microcephaly connection to become apparent?

Zika has now come to the USA, with 40,000 confirmed cases in Puerto Rico, yet Puerto Rico has seen only a small number of microcephaly cases. ( This mirrors the experience of Central American countries, where Zika has spread but microcephaly cases have not dramatically jumped in parallel the way they did in Brazil. This has led to conspiracy theories about pesticides and water in Brazil. (, I propose a simpler, much less controversial explanation:
  • Brazilians eat something regularly that helps Zika virus reach developing fetuses, something otherwise innocuous. 
And that something appears to be water-soluble chondroitin sulfate from cartilage contained in their national dish, feijoada. Feijoada is a black bean stew made with various cuts of meat, most notably pig ears, feet, and snouts (, and the feijoada is typically simmered for hours, an excellent way to extract substances from those meat pieces. Because pig ears are mostly cartilage, they are a very good source of chondroitin sulfate, a supplement made from animal cartilage and used by many for osteoarthritis. (,,

Just under two months ago, researchers identified chondroitin sulfate as a molecule to which Zika binds tightly and which "may be the Zika virus' ticket into the placenta." (, If this finding is correct, then eating extra chondroitin sulfate while pregnant and at risk of Zika virus disease is a terrible idea, for orally-administered chondroitin sulfate is absorbed and increases the amount of chondroitin sulfate in blood plasma. (

I emailed the two corresponding authors of the Zika-chondroitin sulfate April research findings to bring the possible feijoada connection to their attention. I hope my email doesn't end up in their "spam" folders. Maybe the connection I draw here is too simple and has already been dismissed as irrelevant, but it seems like a possibility that should be looked into. In the meantime, if you know a pregnant woman who travels or resides in areas where Zika virus is known to be, you might want to consider warning her to avoid food and drink made with significant amounts of animal cartilage.

* Fun note for my readers: Almost three years ago, I learned of the existence of feijoada because our family studied Brazil for two weeks, and I learned how to cook it. Who knew it might end up relevant to Zika-caused fetal damage?

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