Chlamydia makes men infertile

One of the most common sexually transmitted diseases may be damaging the fertility of British males.

Chlamydia which is known to affect women's fertility by scarring and causing blockages in the fallopian tubes, is now also thought to harm male fertility by causing genetic damage to sperm.

Cases of the sexually transmitted infection have risen in the UK since the mid-1990s and it now affects more than 100,000 people, the majority of whom are in the 18 to 25 age group.

Health Protection Agency figures published in July indicate a 4% rise in chlamydia between 2005 and 2006, from 109,418 cases to 113,585.

Chlamydia is an insidious disease because it often has no obvious symptoms and many of those who test positive are quite unaware they have the infection.

An international team from the U.S., Spain and Mexico analysed sperm from 143 infertile men who were found to have chlamydia and another more mild bacterial infection called mycoplasma.

When a close examination was done on the genetic material in their sperm cells it was revealed that the level of damage or DNA fragmentation in the infertile men's sperm was more than three times higher than in healthy men.

Further tests showed that infected men produced sperm with 80% more physical abnormalities and 10% less mobility.

The doctors then put 95 of the men and their partners on antibiotics for four months and a second genetic analysis at the end of the course of drugs revealed the DNA damage in the men's sperm had typically fallen by 35.7%.

During the course of the treatment 12.5% of the couples achieved a pregnancy, whereas after taking the drugs 85.7% reported a pregnancy.

The scientists suspect the improvement was the result of clearing up the infection in the men, as the damage it causes in women is often irreversible.

The research will be announced at a meeting of the American Society for Reproductive Medicine in Washington this week.