Trichomoniasis is a sexually transmitted infection caused by a tiny germ called trichomonas vaginalis. It can lead to pain and discharge from the vagina or penis, but it often does not cause any symptoms. This means you can pass it on without knowing you have it.
What is trichomoniasis?
Trichomonas vaginalis is a protozoan, which is a tiny germ, similar to bacteria. It can infect your genital area. That is, the vagina and urethra in women, and the urethra and sometimes the prostate gland in men. This infection is passed on to other people by having sex (intercourse). This infection does not usually go further into your body and so does not tend to be as serious as some other sexually transmitted infections (STIs). It can also be completely cured, unlike some other STIs.
As with most STIs, it is most common in younger people under the age of 25. In England, there are ten times as many cases of trichomoniasis in black ethnic minority populations as there are in the general population. Other than in this group of the population, trichomoniasis is uncommon in the UK. (In England in 2016 for example, there were 7,075 new diagnoses of trichomoniasis, compared to 202,546 of chlamydia, 36,244 for gonorrhoea and 31,860 for genital herpes.)
What are the symptoms of trichomoniasis?
- A vaginal discharge is common. This is typically greeny-yellow and may be 'frothy'. The discharge usually has an unpleasant or fishy smell.
- Your vagina and vulva may be itchy and uncomfortable. The irritation may extend into your groin. Sex may be painful.
- You may have pain in the lower part of your tummy (abdomen).
- It may be sore when you pass urine.
- No symptoms occur in some women. However, you can still pass on the infection even if you have no symptoms.
- Discharge from the penis is common.
- It may be sore when you pass urine.
- You may pass urine frequently (due to irritation inside the penis).
- No symptoms occur in most infected men. However, you can still pass on the infection even if you have no symptoms.
How does trichomoniasis occur?
Trichomoniasis is usually passed on by having sex (intercourse) with an infected person. As no symptoms may occur in both men and women who are infected, you can pass on the infection without realising it.
Trichomoniasis is the most common non-viral sexually transmitted infection in the world. It is less common in the UK. However, it is thought that many cases are still not recognised and are not diagnosed. It can be cured with antibiotic treatment.
What are the possible complications with trichomoniasis?
- Pregnancy. If you have untreated trichomoniasis during pregnancy, you have an increased risk of having an early labour and a baby with a low birth weight. You are also more at risk of sepsis after your baby is born.
- In women it may go on to cause pelvic inflammatory disease, and you are more likely to develop another infection called bacterial vaginosis.
- In men, trichomoniasis can, rarely, cause an unpleasant infection of the prostate gland (called prostatitis).
- HIV. If you have untreated trichomoniasis, you have an increased risk of developing HIV infection if you have sex (intercourse) with someone who is infected with HIV.
- Infertility. In both men and women, trichomoniasis can result in reduced fertility.
How is trichomoniasis diagnosed?
You can be tested for trichomoniasis at your GP or by visiting a genitourinary medicine (GUM) clinic. It is important to obtain the correct diagnosis, as the same symptoms can be caused by a number of different infections:
- A sample (swab) of the discharge from your vagina or penis is sent to the laboratory to be tested. This may be taken by a healthcare professional, or they may show you how to take one yourself.
- Trichomoniasis is sometimes seen by chance when a smear test is done in women.
- A sample of urine from men may also show the infection.
What is the treatment for trichomoniasis?
An antibiotic medicine called metronidazole is the common treatment. You and your partner should be given treatment at the same time and you should avoid having sex (intercourse) for at least one week after receiving your treatment.
Tinidazole is an alternative antibiotic medicine that is sometimes used.
Does my sexual partner need treating?
Yes. Even if they do not have symptoms. You and your partner should be treated at the same time. Anybody you have had sex with in the four weeks before your symptoms started should be treated.
Some other points about trichomoniasis
- After you are treated, you may get the infection back if your sexual partner was not treated, or if you have sex with a new partner who has this infection.
- Other STIs are more common in people with trichomoniasis. You (and your partner) may be advised to be tested for other infections.
Further reading and references
Management of trichomonas vaginalis; British Asociation of Sexual Health and HIV (Feb 2014)
Sexually Transmitted Infections in Primary Care; Royal College of General Practitioners and British Association for Sexual Health and HIV (Apr 2013)
Trichomoniasis; NICE CKS, October 2018 (UK access only)
Poole DN, McClelland RS; Global epidemiology of Trichomonas vaginalis. Sex Transm Infect. 2013 Sep89(6):418-22. doi: 10.1136/sextrans-2013-051075. Epub 2013 Jun 6.
Menezes CB, Frasson AP, Tasca T; Trichomoniasis - are we giving the deserved attention to the most common non-viral sexually transmitted disease worldwide? Microb Cell. 2016 Jun 273(9):404-419. doi: 10.15698/mic2016.09.526.
Sexually transmitted infections (STIs): surveillance, data, screening and management; Public Health England, 2016
Gulmezoglu AM, Azhar M; Interventions for trichomoniasis in pregnancy. Cochrane Database Syst Rev. 2011 May 11(5):CD000220. doi: 10.1002/14651858.CD000220.pub2.
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