Zika causes testicles to shrink & infertility in mice, alarming sign for humans – study

© Paulo Whitaker
The mosquito-transmitted Zika virus that is responsible for some irreversible birth defects in babies could also be harmful to male fertility, a new study suggests. Infected mice had shrunken testicles and lower levels of testosterone.

The virus hits male mice’s reproductive system hard, said a study published Monday in Nature magazine.

The lab tests run on mice infected with Zika have shown low sperm counts and testicles reduced 90 percent by weight.

That’s not yet a reason for men to panic, but already a matter for concern and further studies.

“I think this is an important finding [in mice], but this has to be tested in humans… This virus is from a class of viruses that causes cell death in a lot of cells, so it’s not hard to extrapolate that if you had a lot of virus in a tissue for a long period of time, then cells would die. That said, we absolutely don’t know what the extent of this will be in humans… The only way to find out is to track men longitudinally,” Dr Michael Diamond, of the University of Washington, said in an interview with The Scientist.

“Don’t jump to the conclusion right off that this is definitely what is happening to the human,” Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, told AP. But the mouse finding is a “red flag you need to pursue.”

The rodents taking part in the tests were able to impregnate females at one-fourth the normal rate and the litter was less than half the normal number.

The mice’s reduced testicles didn’t heal even six weeks after the virus was gone from their systems. Some researchers believe the damage could be irreversible.

This is the first time that scientists have pointed to serious Zika dangers for men, as the disease has been mostly associated with the dangers for pregnant women, namely their babies potentially born with microcephaly. In rare cases Zika can also trigger Guillain-Barre syndrome followed by paralysis and leading to death.