Levels of evidence (I-IV) and grades of recommendation (A-C) are defined at the end of the "Major Recommendations" field.
Diagnosis
Laboratory Investigations
Females
- Direct observation by wet mount or acridine orange staining is approximately 70% sensitive compared to culture in females, but will only detect about 30% cases in males. Microscopy for Trichomonas vaginalis should be performed as soon as possible after the sample is taken as motility diminishes with time.
- Culture techniques are still regarded as the most sensitive and specific; they provide the "gold standard" against which other methods are judged. (III, B). Culture media vary in efficiency but Diamond's TYM medium (or modified version) is amongst the best.
- Polymerase chain reaction (PCR) based diagnostic tests have recently been developed and sensitivities and specificities approaching 100% have been reported. No PCR assay for T. vaginalis is currently on the market in the United Kingdom (UK). (III, B)
- Trichomonads are sometimes reported on cervical cytology; however a meta-analysis has shown that while it has good specificity the weighted mean sensitivity was only 58%. In such cases it is prudent to confirm the diagnosis, preferably by culture of vaginal secretions. (Ia, A).
Sites Sampled
Females (III, B)
- Swab taken from the posterior fornix at the time of speculum examination.
- Self-administered vaginal swabs have been used in many recent studies, and are likely to give equivalent results.
Males (III, B)
- Urethral culture or culture of first-void urine will diagnose 60-80% cases; sampling both sites simultaneously will significantly increase the diagnostic rate.
Management
General Advice
Sexual partner(s) should be treated simultaneously. Patients should be advised to avoid sexual intercourse (including oral sex) until they and their partner(s) have completed treatment and follow-up.
Patients should be given a detailed explanation of their condition with particular emphasis on the long-term implications for the health of themselves and their partner(s). This should be reinforced by giving them clear and accurate written information.
Further Investigations
Screening for coexistent sexually transmitted infections (STIs) should be undertaken in both men and women.
Treatment
The frequency of infection of the urethra and paraurethral glands in females dictates that systemic chemotherapy be given to effect a permanent cure. Most strains of T. vaginalis are highly susceptible to metronidazole and related drugs (approximately 95% cure rate). There is a spontaneous cure rate in the order of 20-25%.
Recommended Regimes (IIb)
- Metronidazole 2 g orally in a single dose
or
- Metronidazole 400-500 mg twice daily for 5-7 days
The single dose has the advantage of improved compliance and being cheaper; however, there is some evidence to suggest that the failure rate is higher, especially if partners are not treated concurrently.
Alternative Regimens
Tinidazole 2 g orally in a single dose
Tinidazole has similar activity to metronidazole but is more expensive.
Caution
Patients should be advised not to take alcohol for the duration of treatment and for at least 48 hours afterwards because of the possibility of a disulfiram-like (Antabuse® effect) reaction.
Allergy
There is no effective alternative to 5-nitroimidazole compounds. In cases of true allergy, desensitization to metronidazole has been described and could be considered.
Pregnancy and Breast Feeding
Meta-analyses have concluded that there is no evidence of teratogenicity from the use of metronidazole in women during the first trimester of pregnancy (Ia). The British National Formulary advises against high dose regimens in pregnancy.
Metronidazole enters breast milk and may affect its taste. The manufacturers recommend avoiding high doses if breastfeeding.
Treatment Failure (IV or anecdotal)
- Check compliance and exclude vomiting of metronidazole
- Check possibility of re-infection
- Check partner(s) has been treated
- Patients who fail to respond to first course of treatment often respond to a repeat course of standard treatment.
If this fails and above excluded, the treatment of patients with metronidazole-refractory vaginal trichomoniasis constitutes a major therapeutic challenge, and treatment options are extremely limited. Sensitivity testing is currently unavailable.
- It has been suggested that some organisms present in the vagina may interact to reduce the effectiveness of nitroimidazole and that use of a broad spectrum antibiotic such as with erythromycin or amoxycillin before re-treating with metronidazole will improve the chances of cure.
- Higher doses of metronidazole
- Metronidazole 400 mg three times daily with metronidazole 1 g per rectum daily for 7 days or longer (some clinicians have added zinc sulphate 1% vaginal douches or vaginal washes with 3% acetic acid to the regimen)
- Metronidazole 2 g daily for 3 days to 5 days
- High dose intravenous metronidazole
- High doses of oral tinidazole e.g. 2 g twice daily for 2 weeks, with or without intravaginal tinidazole
There are anecdotal reports of treatment success with the following regimens, most of which are not readily available in the UK. It should be noted that most of these are based on success in one or two patients, each of whom had previously received a wide variety of treatments. The definition of cure was variable and microbiological follow up was not available in all cases. Additionally for each case report of cure with specific treatment, there are reports of failure with the same agents. (IV or anecdotal).
- 6% Nonoxynol–9 pessaries nightly for 2 weeks and then once weekly for up to 7 months
- Acetarsol pessaries 2 x 250 mg nightly for 2 weeks
- Paromomycin sulphate 250 mg pessaries once or twice daily for 2 weeks
Management of Sexual Partners
- Current partners should be screened for the full range of sexually transmitted infections and treated for T. vaginalis irrespective of the results of investigations (Ib, A).
- In a male contact of T. vaginalis, found to have non-gonococcal urethritis (NGU) on screening, it is reasonable to treat initially for T. vaginalis and repeat the urethral smear before treating additionally for NGU (III).
T. vaginalis in Children
Trichomonas may be acquired perinatally and occurs in about 5% of babies born to infected mothers. Infection in prepubescent girls is unusual. Infection beyond the first year of life should suggest sexual contact (although other modes of transmission are also postulated) and the child should be appropriately evaluated.
Follow up
Tests of cure are only recommended if the patient remains symptomatic following treatment, or if symptoms recur (IV, C).
Definitions:
Levels of Evidence
Ia: Evidence obtained from meta-analysis of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well designed controlled study without randomization
IIb: Evidence obtained from at least one other type of well designed quasi-experimental study
III: Evidence obtained from well designed non-experimental descriptive studies such as comparative studies, correlation studies, and case control studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
Grading of Recommendations
A (Evidence Levels Ia, Ib)
- Requires at least one randomised controlled trial as part of the body of literature of overall good quality and consistency addressing the specific recommendation.
B (Evidence Levels IIa, IIb, III)
- Requires availability of well conducted clinical studies but no randomised clinical trials on the topic of recommendation.
C (Evidence Level IV)
- Requires evidence from expert committee reports or opinions and/or clinical experience of respected authorities.
- Indicates absence of directly applicable studies of good quality.
