What Is Trich (Trichomoniasis)? Parasitic STI Guide
Trich ('trick') is trichomoniasis — infection by a flagellated parasite called Trichomonas vaginalis, the most common curable STI worldwide with ~2.6 million US infections. It causes frothy, foul-smelling discharge and itching when symptomatic (most cases stay quiet), spreads through genital contact, and cures completely with metronidazole — provided both partners treat simultaneously.
The organism behind 'trick'
Trichomonas vaginalis is a single-celled protozoan — a microscopic swimmer propelled by four front flagella and an undulating membrane. It infects only human urogenital tissue: squamous cells of the vagina, urethra and paraurethral glands. Outside the body it dies quickly (minutes to hours when damp), which confines its highway to direct genital contact.
Why the slang matters for searchers: people type "trick," "trich," and "trich" interchangeably — all pointing at the same parasite. The clinical name remains trichomoniasis; testing codes say T. vaginalis NAAT.
Scale check: the most common curable STI on Earth — more prevalent than chlamydia and gonorrhea combined in many populations, yet absent from most routine panels (panel gaps explained).
Recognizing trich (when it cooperates)
| Feature | Typical trich presentation |
|---|---|
| Discharge | Frothy, thin, yellow-green (women); men usually none |
| Odor | Strong fishy/musty smell (odor decoder) |
| Itching/irritation | Vulvar/vaginal burning; inner-thigh soreness possible |
| Urinary symptoms | Burning, frequency mimicking UTI |
| Exam finding | 'Strawberry cervix' — punctate red spots (provider-visible only) |
| Silence factor | ~70–85% show nothing at all |
Symptom onset runs 5–28 days post-exposure when symptoms bother appearing (timing chart).
The cure and the ping-pong problem
- Treatment: oral metronidazole — 500mg twice daily × 7 days preferred for women (higher cure rates), or 2g single dose (standard for men). Tinidazole works equivalently.
- Alcohol ban: none during treatment plus 3 days after — the reaction is severe nausea/vomiting.
- Simultaneous partner treatment: non-negotiable. Trich reinfection rates are the highest of any STI precisely because one partner treats while the other keeps carrying.
- Retest: 2 weeks to 3 months after treatment confirms cure and catches ping-pong early (testing windows).
Why bother with a 'mild' parasite: untreated trich roughly doubles HIV acquisition risk, associates with preterm birth, and fuels pelvic discomfort — cheap pills versus real consequences (drug guide).
Distinguishing it from lookalikes: BV comparison, classification deep-dive, yeast differences.
Frequently asked questions
Sources & further reading
- 📚 CDC — Trichomoniasis — www.cdc.gov/trichomoniasis/about
- 📚 CDC — Treatment guidelines — www.cdc.gov/std/treatment-guidelines/trichomoniasis.htm
- 📚 WHO — STI fact sheet — www.who.int/news-room/fact-sheets/detail/sexually-transmitted-infections-(stis)