The Zika virus ‘could SHRINK a man’s balls, lower his testosterone levels and leave him infertile’
The mosquito-borne virus has already been shown to cause severe birth defects and neurological problems
THE Zika virus could shrink a man's testicles, lower his testosterone levels and leave him infertile, experts warned today.
Though the new findings are in mice, scientists say the discovery could have worrying consequences for men infected by the mosquito-borne virus.
To date, much of the research around Zika has focused on how it affects pregnant women and causes severe birth defects in unborn babies.
Studies have also shown it increases the risk of developing Guillain-Barré syndrome, which can leave a person temporarily paralysed.
But now, there are fears a man's fertility could be affected - after a US study found the virus targets the male reproductive system.
Three weeks after male mice were infected with Zika, their testicles had shrunk, levels of their sex hormones had dropped and their fertility was reduced.
As a result, these mice were less likely to impregnate female mice.
Professor Michael Diamond, co-senior author of the study, from Washington University School of Medicine, said: "We undertook this study to understand the consequences of Zika virus infection in males.
"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."
Some clinical reports of pain in the lower pelvis of Zika patients, and blood in their sperm would be consistent with a similar effect happening in humans
Dr Derek Gatherer, Lancaster University
The virus persists in men's semen for months, studies have already revealed.
The US Centers for Disease Control and Prevention recommend that men who have travelled to a Zika-endemic region use condoms for six months, regardless of whether they have had symptoms of Zika infection.
It is not known, however, what impact this lingering virus can have on men's reproductive systems.
To explore the issue, researchers injected male mice with the virus.
After one week they noted it had already reached the testicles, which showed signs of inflammation.
Two weeks into the experiment, the team found the testicles were significantly smaller, their internal structure was collapsing, and many cells were dead or dying.
After three weeks, the mice's testicles had shrunk to one-tenth their normal size, and the internal structure was completely destroyed.
Related Stories
The mice were monitored for six weeks - during which time their testicles did not heal, even though the virus had cleared from their bloodstream.
Prof Diamond said the damage done is likely to be permanent.
"We don't know for certain if the damage is irreversible, but I expect so, because the cells that hold the internal structure in place have been infected and destroyed."
As the testicles are responsible for producing sperm and testosterone, the scientists noted the mice's sperm counts plummeted.
At the six-week mark, the number of motile sperm had fallen tenfold, and testosterone levels were similarly low.
Co-author Dr Kelle Moley said: "This is the only virus I know of that causes such severe symptoms of infertility.
"There are very few microbes that can cross the barrier that separates the testes from the bloodstream to infect the testes directly."
Dr Derek Gatherer, from Lancaster University, who did not take part in the study, said while it's known the virus finds its way into the reproductive organs, and is sexually transmitted, this is the first evidence "this passage through the reproductive tract may actually be damaging".
Our study... does suggest that men might face low testosterone levels and low sperm counts after Zika infection, affecting their fertility
Professor Michael Diamond, Washington University School of Medicine
He said: "Some clinical reports of pain in the lower pelvis of Zika patients, and blood in their sperm would be consistent with a similar effect happening in humans."
While there have been no reports linking infertility in men to Zika infection, Dr Moley said it can be a difficult symptoms to identify in surveys.
"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.
"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."
Men with low testosterone, detected via blood test, are at risk of a low sex drive, erectile dysfunction, fatigue and loss of body hair and muscle.
Prof Diamond said human studies are now needed to ascertain the impact of infection in men.
The study is published in the journal Nature.
