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Trichomoniasis: an overlooked sexual infection

Chris Faldon
MSc BSc(Hons) Nursing DipHV RGN
Public Health Infection Control Nurse
Borders Public Health Department

Former Vice-President
Society of Health Advisers in Sexually Transmitted Diseases

Trichomonas vaginalis (TV) is a parasitic organism - a flagellated protozoan. It is almost exclusively acquired through sexual contact, usually male to female (and vice versa). Female-to-female transmission has been reported, but male-to-male is very rare.(1)
Trichomoniasis is considered to account for half of all curable sexually transmitted infections (STIs) globally. An estimated 167 million cases occur each year. Between 1990 and 1999, trichomoniasis in men seen at genitourinary medicine (GUM) clinics in England, Wales and Northern Ireland doubled, but remained fairly static in women.(2) Table 1 looks at the different presentations of trichomoniasis depending on gender.


It would be a mistake to conclude that trichomoniasis  is a minor infection. It is an important pathogen that affects women during pregnancy. Evidence is gathering for an association with premature labour, low birthweight and prostatitis.(4) Also, although this has not yet been clearly established, it appears to play a significant part in HIV transmission.(5)

In women the organism is found in the vagina, urethra and paraurethral glands. A single high vaginal swab sent in charcoal-based transport medium is adequate to diagnose trichomoniasis.(6) In men infection is usually of the urethra, although trichomonads have been isolated from the subpreputial sac and lesions of the penis. In general, diagnosis is much more difficult for males - the best culture results are yielded by combining urethral swabs and urine sediment.
Microscopy has been the most practicable means of diagnosis for routine screening of T vaginalis. It is highly specific and easily performed, but it fails to detect 30-50% of TV infections. Culture is therefore regarded as the "gold standard". Newer polymerase chain-reaction (PCR) techniques have been shown to be very sensitive and hold great potential for self-swabbing.
Cervical cytology sometimes picks up the presence of trichomonads. However, the sensitivity is approximately 60-80%, and there is a false-positive rate of about 30%. It is recommended that in such cases the ­diagnosis is confirmed by direct observation of vaginal secretions and preferably by culture, if available. This may necessitate a referral to the GUM clinic.

Most strains of T vaginalis can be effectively treated with metronidazole and related drugs. It is estimated that there is a spontaneous cure rate in the order of 20-25%. Table 2 lists the recommended regimens for treatment.


Treatment failure can occur and it is worth excluding the following:

  • Poor compliance.
  • Reinfection due to untreated partner(s).

A repeat course of standard treatment is usually successful. Metronidazole treatment failure is not uncommon, but genuine anti­biotic resistance is likely to play only a small part in this.

Further management
Essential elements of care include:

  • Giving diagnosis and correct information about TV.
  • Giving correct treatment.
  • Offering testing for other STIs.
  • Giving advice regarding reinfection.
  • Discussing partner notification and management.
  • Providing sexual health education and backup ­literature.
  • Arranging follow-up at the end of treatment.
  • Encouraging referral to a GUM clinic.

Cases detected in the primary care setting can be simply treated with the appropriate antibiotic; however, further considerations need to be taken into account. TV is a particularly sensitive marker of high-risk sexual behaviour and, as such, concomitant infections are frequently observed. Ideally, anyone complaining of an altered discharge should be examined and tested appropriately. A referral to a GUM clinic should be considered even if at first mention the patient is against such a proposal. Attendance has doubled to GUM clinics over the past decade, which is an encouraging sign that the stigma attached to seeking out help is diminishing.(9)
The National Sexual Health and HIV Strategy invites primary care to play a greater role in sexual health.(10)  GPs and practice nurses require the clinical skills that will enable them to detect STIs.(11) Diagnostic confirmation and clear models for management and referral will be required to provide a more effective service. Optimal management depends on close links between primary care and genitourinary medicine.(12) In doing so, mutual understanding can be increased and issues surrounding referral and attendance clarified.
Where screening for STIs occurs, the essential elements of care mentioned earlier should be covered adequately. If positive results are infrequent there may be an insufficient knowledge base, lack of experience or discomfort in discussing intimate details with a patient. This is true particularly where partner notification and recent sexual history are concerned. The structures to deal with partners, past and present, do not exist in primary care. This is problematic, and it is crucial that primary care practitioners do not ignore this but instead seek out creative solutions. A striking difference in the number of diagnoses seen in GUM clinics between men and women is probably due to the largely asymptomatic presentation in males.(13) Proactive partner management is therefore essential for infection control. Current partners should be screened for the full range of STIs and treated for TV irrespective of the results of investigations. Key links should be established with health advisers based in GUM clinics. They have an established national network of contact tracing and can facilitate the attendance of partners.
Improved undergraduate, postgraduate and in-service training will undoubtedly help. Opportunities to participate in multidisciplinary sexual health educational initiatives should be fostered for professional development.

Trichomoniasis should never be classed as a minor STI. It is true that diagnosed cases can usually be swiftly eradicated. Its asymptomatic nature in men has led to the existence of a large pool of infection in the community. As such it poses a threat to sections of the sexually active population. This relates in part to the growing awareness of its part in obstetric complications and also its role in facilitating the transmission of other STIs, including HIV.
Any STI diagnosis commonly carries with it complex emotional and social issues. Adequate time, resources and skills are needed if patients are to receive optimal care. This can be better achieved when professionals involved in testing and treating such infections collaborate with one another. This can be at the level of service delivery as well as education.


  1. Clinical Effectiveness Group (Association for Genitourinary Medicine and the Medical Society for the Study of Venereal Diseases), Sherrard J. National guidelines on the management of Trichomonas vaginalis treatment. 2001. Available from URL:
  2. PHLS. Sexually transmitted ­infections quarterly report: bacterial vaginosis, candidiasis and Trichomonas vaginalis in the United Kingdom. CDR weekly 2002;12(22). Available from URL:
  3. Faldon CM. Sexual infections. In: Manual of health advising practice. London: Department of Health and SHASTD; 2003 (in press ­- look out for further details on the SHASTD website -
  4. Berghella V, Klebanoff M, McPherson C, et al. Sexual intercourse association with asymptomatic bacterial vaginosis and Trichomonas vaginalis treatment in relationship to preterm birth. Am J Obstet Gynecol 2002;187:1277-82.
  5. Schwebke JR. Update of ­trichomoniasis. Sex Transm Infect 2002;78(5):378-9.
  6. Newcastle GUM Clinic. Guidelines for common conditions and situations seen in general practice and genitourinary medicine. 2002. Available from URL:­documents/grand%20GP%20guide.doc
  7. Garrow SC, Smith DW, Harnett GB. The diagnosis of chlamydia, gonorrhoea, and trichomonas infections by self obtained low vaginal swabs, in remote northern Australian clinical practice. Sex Transm Infect 2002;78:278-81.
  8. Pattman RS. Recalcitrant vaginal trichomoniasis. Sex Transm Infect 1999;75:127-8.
  9. Foley E, Patel R, Green N, Rowen D. Access to genitourinary medicine clinics in the United Kingdom. Sex Transm Infect 2001;77:12-4.
  10. Department of Health. The national strategy for sexual health and HIV. London: Department of Health; 2001.
  11. Rogstad KE, Davies A, Krishna Murphy S. Management of Chlamydia trachomatis: combined community and hospital study. Sex Transm Infect 2000;76:493-4.
  12. Matthews P, Fletcher J. Sexually transmitted infections in primary care: a need for education. Br J Gen Pract 2001;51:52-6.
  13. PHLS Standard Operating Procedure. Investigation of genital tract and associated specimens. Available from URL:

Society of Health Advisers in Sexually Transmitted Diseases