We usually hear about the Zika virus in connection with women, pregnancy, and birth defects, but researchers have found that the virus may also interfere with male fertility.
In a study recently published in Nature, male laboratory mice had diminished levels of sex hormones, and shrunken testicles three weeks after being infected with Zika.
“While our study was in mice - and with the caveat that we don’t yet know whether Zika has the same effect in men - it does suggest that men might face low testosterone levels and low sperm counts after Zika infection, affecting their fertility,” said study co-author Michael Diamond, M.D., Ph.D.
A week after the mice were injected with Zika, the virus had migrated to their testes, triggering microscopic markers of inflammation. During the second week the internal testes structure collapsed, and many cells died, leaving the testicles appreciably reduced. Twenty-one days into the study, with the internal structures decimated, the rodent’s testicles were down to one-tenth their normal size.
As the mice testes sustained increasing damage, testosterone levels and sperm counts dropped drastically. After six weeks of infection, the motile sperm count had declined tenfold. The scientists don’t know whether the testicle damage is irreversible, but it seems likely since the internal scaffolding is destroyed.
“This is the only virus I know of that causes such severe symptoms of infertility,” says Diamond’s colleague Kelle Moley, M.D. “There are very few microbes that can cross the barrier that separates the testes from the bloodstream to infect the testes directly.”
Although it’s likely male human fertility will also be diminished by Zika infections, the researchers don’t know whether human testes will noticeably shrink in size, as with the mice. “People often don’t find out that they’re infertile until they try to have children, and that could be years or decades after infection,” notes Moley.
“I think it is more likely doctors will start seeing men with symptoms of low testosterone, and they will work backward to make the connection to Zika.”
Source: Science Daily