Chlamydia can make men infertile by damaging the quality of their sperm, new research has shown.

The sexually transmitted disease usually goes undetected in men and has long been known to threaten female fertility. But now, scientists from Spain and Mexico have now established that it presents similar infertility risks for men.

Men with chlamydia have three times the normal number of sperm with genetic damage that can impair their ability to father children, the study found.

Antibiotic treatment can reverse the effect, and preliminary results indicate that it may dramatically enhance pregnancy rates when couples are trying for a baby.

But the discovery suggests that the prevalence of the disease may be contributing to infertility across an entire generation of young adults.

In the study, a team led by José Luis Fernández, of the Juan Cana-lejo University Hospital in La Coruña, Mexico, examined sperm samples taken from 193 men seeking fertility treatment with their partners in Monterey, Mexico.

Of these, 143 were infected with both chlamydia and mycoplasma, another common sexually transmitted bacterium, while 50 were uninfected and served as healthy controls.

Fernández, who will present his findings Monday at the American Society for Reproductive Medicine conference in Washington, then examined the men’s sperm for a form of genetic damage called DNA fragmentation. This can cause sperm to die, as well as hindering their ability to fertilize eggs and embryonic development.

An average of 35 percent of the infected men’s sperm was damaged, a proportion 3.2 times higher than in the healthy controls.