| disease | Vaginal Trichomoniasis |
| alias | Trichomonal Vaginitis |
Trichomonal vaginitis is a common gynecological disease caused by Trichomonas vaginalis. The parasite can be directly transmitted to women through sexual intercourse, as the same type of trichomonad is often found in the urethral and prostatic secretions of the patient's husband. Trichomonads not only inhabit the vagina but can also reside in the lower urinary tract (urethra and paraurethral glands) and the cervical canal. Even carriers of trichomonads may not exhibit any clinical symptoms. Trichomonads in the vagina consume glycogen, altering the vaginal pH and disrupting its defense mechanisms, making secondary infections more likely. Therefore, such carriers often develop trichomonal vaginitis when the vaginal environment changes after menstruation (or during pregnancy, postpartum, or after late abortion), creating favorable conditions for trichomonad growth and reproduction. However, this is relatively rare. The reason may be that trichomonads rely on glycogen as their food source. Before puberty and after menopause, women have poor ovarian function and low estrogen levels, leading to a lack of glycogen in the vaginal mucosal epithelium. As a result, these conditions are less conducive to trichomonad growth and reproduction, making trichomonal vaginitis less common in these groups.
bubble_chart Epidemiology
Trichomonal vaginitis is widespread around the world. It is estimated that 3 million women are infected annually in the United States, and 180 million worldwide. Foreign data indicate that the rate of trichomoniasis infection is related to the frequency of sexual contact, with the infection rate among adult virgins being zero. In China during the 1950s, the infection rate among married women was about 20%, but it significantly declined by the 1970s. In recent years, due to the influence of the sexual liberation ideology in some foreign countries or regions, the incidence of vaginal trichomoniasis has risen again, with the sexually active age group being the most susceptible.
The source of the epidemic is trichomoniasis patients and carriers, primarily transmitted directly through sexual intercourse, but it can also spread indirectly through public baths, swimming pools, and seated toilets.The three types of Trichomonas are morphologically similar, with Trichomonas vaginalis being the largest. However, there are differences in size, growth capacity, virulence, and antigenic characteristics among strains. Trichomonas vaginalis only has a trophozoite stage and lacks a cystic stage. The trophozoite is pear-shaped or round, measuring 7-32 μm in length—approximately 2-3 times the size of a polymorphonuclear leukocyte—and is colorless, transparent, and refractive. At the anterior end, there are five basal body complexes arranged in a ring, from which four anterior flagella and one posterior flagellum emerge, along with an undulating membrane and a basal chromatic rod. The nucleus is located in the anterior third of the organism, appearing as an oval vesicular nucleus, with a parabasal body and parabasal fibers nearby. A single axostyle runs longitudinally through the organism and extends from the posterior end.
Transmission electron microscopy reveals that the organism is surrounded by a double-layered plasma membrane. In the anterior third, there is an oval nucleus with a double-layered nuclear membrane containing nuclear pores. Inside the nucleus, there are 6-10 chromatin particles of similar size and high electron density. Endoplasmic reticulum is visible around the nuclear membrane, and a Golgi complex is located dorsally between the nucleus and the parabasal fibers. The anterior basal body complex consists of three parts: the flagellar canal lumen, a "C"-shaped shield structure, and five basal bodies.
Trichomonas vaginalis is an anaerobic protozoan with strong adaptability to external environments. It can grow and reproduce at temperatures between 25-42°C and survive for up to 21 days at 3-5°C. Its viability is poorer in semi-dry conditions but can still persist for 6 hours. The optimal pH for growth and reproduction is 5.5-6.0, while pH >7.5 or pH <4.5時，生長受抑制。
Ultrastructural observations show that it lacks complete mitochondria, which significantly differs from other protozoa. It exhibits neither photophobia nor phototaxis and tends to move toward the cathode under electric current.
In human body fluids, its state varies: it can be observed reproducing in leucorrhea and semen but not in urine. The organism undergoes both anaerobic and aerobic metabolism, including glycolysis. Enzymes of the ACA cycle are largely present within the organism, and the cellular respiratory pigment system includes ATPase. It can utilize nutrients such as glycogen, glucose, fructose, various amino acids, and proteins. Adding glucose to the culture medium similarly promotes vigorous reproduction.
The pathogenicity of vaginal trichomonads varies depending on the strain, host physiological status, immune function, endocrine factors, and bacterial or fungal infections in the vagina, particularly when women experience physiological imbalances during pregnancy or in the genitourinary system, making them more prone to inflammation. A few days after infection, the vaginal mucosa exhibits congestion, edema, degeneration and shedding of epithelial cells, and an inflammatory leukocyte response. In healthy women, the vagina maintains a pH between 3.8 and 4.4 due to the action of lactobacilli, which inhibits the growth of other bacteria and is unfavorable for trichomonad growth, a phenomenon known as the self-cleaning effect of the vagina. However, trichomonads consume glycogen in the vaginal middle consumptive thirst, hindering the fermentation of lactobacilli and affecting lactic acid concentration, thereby shifting the vaginal pH to neutral or alkaline. The physiological cycle of the vagina after pregnancy and menstruation brings the pH closer to neutral, creating favorable conditions for trichomonad proliferation, leading to higher infection and recurrence rates.
bubble_chart Clinical Manifestations
The incubation period is typically 4-7 days. In women, infections often manifest as persistent vaginitis, with onset that can be either sudden or gradual. Trichomonal vaginitis primarily presents with increased vaginal discharge, which is frothy, foul-smelling, and yellow-green in color. Symptoms include dysuria and vulvar cutaneous pruritus. The acute phase may last from one week to several months, with fluctuations in severity, dyspareunia, and worsening symptoms post-menstruation. Subsequently, leukorrhea decreases, symptoms alleviate, and may even disappear entirely, but the patient becomes a carrier. At the time of initial diagnosis, 50% of female patients are asymptomatic. If Trichomonas vaginalis infects the urethra or bladder, it can lead to trichomonal urethritis or cystitis. Trichomonas vaginalis can also engulf sperm, leading to infertility. Some reports suggest that Trichomonas vaginalis may cause cellular developmental abnormalities and nuclear anomalies, thereby significantly increasing the incidence of cancer compared to women without trichomoniasis. Examinations may reveal findings ranging from grade I congestion in the vaginal fornix and cervix to extensive erosions, petechiae, perianal erosions, a granular and friable appearance, and hyperemic endometrium (strawberry cervix).
bubble_chart Auxiliary Examination
1. Hanging Drop Method:
The hanging drop method is the simplest way to examine vaginal trichomonads, with a positive rate of 80–90%. The specimen is smeared on a slide, a drop of saline is added, and then covered with a coverslip. Examination under 100–200x magnification reveals the flagellar undulating membrane movement of the protozoa. Adding 5% neutral red to the saline does not kill the trichomonads or stain them, but the surrounding area turns pink, making the white protozoa easier to identify. Alternatively, a drop of 1600x acridine orange solution can be added to a fresh specimen and observed under a fluorescence microscope, where the organisms exhibit a pale yellow-green fluorescence, which is particularly striking. The direct microscopy method has a very high detection rate.
2. Smear Staining Method:
The secretion is smeared on a slide and allowed to air-dry before staining with various dyes, such as Gram stain, Wright stain, Giemsa stain, PAS stain, or Leishman stain. This method not only reveals the shape and contents of the trichomonads but also allows observation of other microorganisms present in the vagina. Acridine orange staining with fluorescence microscopy can also be used.
3. Culture Method:
Vaginal or urethral secretions are added to a culture medium and incubated at 37°C for 48 hours, with subcultures performed every 72 hours. A drop of the mixed culture is smeared on a slide, stained, and examined under a microscope.
4. Immunological Methods:
These methods detect specific antigens of vaginal trichomonads. Commonly used immunological techniques include fluorescent antibody testing, ELISA, and latex agglutination, which have higher positive rates than smear methods. However, immunological methods are generally not used in clinical practice.
1. Trichomoniasis of the vagina: ① Increased vaginal discharge with a foamy appearance; ② The cervix and vaginal walls show a characteristic strawberry-like appearance. Trichomonad test is positive.
2. Male trichomonal non-gonococcal urethritis: ① Grade I redness and swelling of the urethral orifice, with a small amount of mucous, purulent, or bloody discharge; ② May be accompanied by cystitis or pyelonephritis; ③ Trichomonad test is positive.
bubble_chart Treatment Measures
1. Topical Medication
To enhance vaginal defense, after washing the vagina with a soap-soaked cotton ball, rinse with 0.5% lactic acid, nitric acid, or a 1:5000 potassium permanganate solution. For bacterial infections, use a 1:2000 benzalkonium chloride solution for rinsing. Choose one of the following options: - Devegan tablets: Insert one tablet daily into the vaginal fornix for 10 days as one course. - Carbarsone tablets: Insert 0.2-0.4g into the posterior vaginal fornix daily for 7-10 days as one course. - Trichomycin: Insert 100,000 units into the vagina daily for 10 days as one course. - Azalomycin: Insert one tablet into the vagina daily for 7-10 days as one course. Before topical medication, rinse the vagina with 0.5% vinegar solution to improve efficacy.
2. Chinese Medicinals Treatment
Focus on clearing heat, drying dampness, and killing parasites. Commonly used herbs include: - Sophora 30g, - Phellodendron Bark 15g, - Poria 30g, - Densefruit Pittany Root-bark 30g. Decoct with water and use to wash the vulva and rinse the vagina. Then insert a suppository made of Cnidium Fruit and Sophora (9g each) into the vagina daily for 10 days as one course.
3. Systemic Treatment
Oral metronidazole (Flagyl): - 500mg twice daily for 7 days, or - A single 2.0g dose. Concurrent treatment of sexual partners is crucial. Single-dose therapy may also be chosen. Metronidazole is highly effective, but highly resistant strains of vaginal trichomonads have been isolated from treatment-resistant cases. Due to its disulfiram-like effect, alcohol must be avoided during treatment and for 24 hours after completion. As metronidazole is carcinogenic in rodents and mutagenic in bacteria, it should not be used during the first trimester of pregnancy. After the third month of pregnancy, a single 2.0g oral dose may be administered.
Treatment Notes: After a negative trichomonad test, recheck after menstruation and continue treatment for two additional courses post-menstruation to consolidate results. Three consecutive months of negative tests confirm cure. Emphasize that both the patient and their partner must take medication to ensure complete cure and prevent recurrence.
Strengthen health education, conduct general surveys and treatment, eliminate sources of pestilence, enforce strict management systems, prohibit patients from entering swimming pools, improve public health facilities, and ensure medical units implement disinfection and isolation to prevent cross-infection. For persistent recurrent cases, it is advisable to examine the male partner's urine or prostatic fluid for trichomonads to facilitate simultaneous treatment and control recurrence.
1. Candidal vaginitis: vulvovaginal cutaneous pruritus, cheesy or beancurd-like leucorrhea, white pseudomembrane in the vagina. Fungal test positive.
2. Bacterial vaginosis: ① Non-purulent grayish-white sticky vaginal discharge; ② Vaginal discharge has a fishy odor, amine test positive; ③ Elevated pH value of vaginal discharge, 5.0-5.5; ④ Presence of clue cells in the discharge.
