A new strain of chlamydia that may make it easier to catch HIV is becoming “widespread” among gay and bisexual men, a sexual health charity has warned.

According to Terrence Higgins Trust (THT), lymphogranuloma venereum, or LVG, is a serious sexually transmitted infection that attacks the lymph nodes.

It first arrived in the UK in 2004 and has been spreading in gay and bisexual men. Last year, 193 men were diagnosed with the infection and, in the first six months of 2010, 190 men have been diagnosed, many of whom also have HIV.

Symptoms include constipation, bleeding and discharge from the rectum, painful inflammation and painful anal abscesses or ulcers. Left untreated, the infection can cause serious damage and in severe cases, can permanently damage the rectum and require surgery.

Having the infection makes it more likely men will catch diseases such as HIV, hepatitis C and syphilis.

THT say that in most cases, LGV was caught anally and activities such as unprotected anal sex, fisting or sharing sex toys can spread the disease. Men are encouraged not to share sex toys or put a fresh condom on them between each new partner.

The charity also advises men who believe they may have picked up the infection to visit a sexual clinic as GPs may misdiagnose the problem. If caught early, LGV can be cured within three weeks with antibiotic use.

Alan Wardle, head of health promotion at THT, said: “LGV is a newcomer to the gay scene, and a particularly nasty one. Not only are its symptoms pretty unpleasant, having LGV means it’s much easier to pick up or pass on other STIs, including HIV, Hep C, and syphilis.

“Early warning signs that you may have LGV include constipation, inflammation, pain or bleeding from the rectum. If you start showing these symptoms, the best thing to do is quickly get yourself to the nearest GUM clinic for a test. When going for a check-up, ask for your bum to be checked for chlamydia if the clinic doesn’t already do this. And don’t have any kind of sex until you’ve been checked and treated.”