Zika and Male Fertility

Men thought they had dodged a bullet when the Centers for Disease Control and Prevention first announced that the Zika virus was making its way to North America. After all, the dread disease only seemed to affect women and newborn babies.

Now, however, all bets are off.

Studies and reports indicating that the Zika virus can do grave damage to the testes of male mice are now being published. One such study, from a team at Yale and the Howard Hughes Medical Institute, found that Zika attacked specialized cells that produce testosterone and support sperm production in mice. Three weeks after infection, the mouse testes were much smaller than those of uninfected mice and contained far less testosterone, and the virus continued to replicate in testicular cells even after it was cleared from the blood.

“No one has really correlated this to infertility in men,” said Kelle Moley, MD, co-director of the Institute of Clinical and Translational Sciences at Washington University in St. Louis, “but infertility is not something that comes to the forefront when you have a cold. No one is going to get a semen analysis on someone who has a fever and a rash and chills. We may not know if people are infertile because of Zika for 20 or 30 years.”

Researchers from the CDC are now working closely with a fertility clinic in Puerto Rico that was hard-hit by Zika. They are trying to determine if men infected by the virus have lower sperm counts or sperm that doesn't work as well in the weeks and months after infection.

Tyler Sharp, PhD, chief epidemiologist at the CDC’s Dengue Branch in San Juan, Puerto Rico, says that so far, he has not heard any case reports from Brazil or other countries with widespread Zika outbreaks of reproductive effects or shrinkage of the testes in men. He is hopeful that what is reported to be happening in mice is not happening in men. Scientists usually use mice to study a disease because they see an effect in humans and use the mice to take a closer look at an animal model. This is the opposite of what the CDC is trying to do.

Moley's team discovered that the virus attacks cells that are responsible for building a barrier between sperm and blood. This divide is crucial because it hides the sperm from attack by the body’s own immune system. When the wall is breached, the immune system kicks in, and by about three weeks after infection very little of the internal architecture of the testes is left.

Sources:  Centers for Disease Control and Prevention