Sexually Transmitted Infections: Trichomonas Vaginalis

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Chapter 57 Sexually Transmitted Infections: Trichomonas Vaginalis

INTRODUCTION

Description: Infection by the anaerobic flagellate protozoan, Trichomonas vaginalis is most often acquired by sexual contact with an infected person.
Prevalence: Roughly 3 million cases per year, 25% of “vaginal infections.”
Predominant Age: 15 to 50 (may occur at any age).
Genetics: No genetic pattern.

ETIOLOGY AND PATHOGENESIS

Causes: T. vaginalis, an anaerobic flagellate protozoan.
Risk Factors: Multiple sexual partners, vaginal pH that is less acidic. (Blood, semen, or bacterial pathogens increase the risk.) Of asymptomatic partners of women with Trichomonas infections, 30% to 80% have a positive culture. The incubation period for Trichomonas infections is thought to be between 4 and 28 days. Trichomonas has been reported (rarely) in virginal patients, supporting the possibility of nonsexual transmission.

CLINICAL CHARACTERISTICS

Signs and Symptoms

• Forty percent may be asymptomatic; a carrier state may exist for many years
• Vulvar itching or burning
• Copious discharge with a rancid odor (generally thin, runny, and yellow–green to gray in color, “frothy” in 25%)
• “Strawberry” punctation of the cervix and upper vagina (15%)
• Dysuria
• Dyspareunia
• Edema or erythema of the vulva

DIAGNOSTIC APPROACH

Differential Diagnosis

• Bacterial vaginitis
• Bacterial vaginosis
• Chlamydial cervicitis
• Gonococcal cervicitis

Associated Conditions: Other sexually transmitted infections (specifically, gonorrhea and chlamydial infection).

Workup and Evaluation

Laboratory: Culture or monoclonal antibody staining may be obtained but are seldom necessary. Evaluation for concomitant sexually transmitted infections should be strongly considered. Detection of Trichomonas by Pap test results in an error rate of 50%. (Alternative tests include OSOM Trichomonas Rapid Test [Genzyme Diagnostics, Cambridge, Massachusetts], an immunochromatographic capillary flow dipstick technology, and the Affirm VP III [Becton Dickinson, San Jose, California], a nucleic acid probe test that evaluates for T. vaginalis, Gardnerella vaginalis, and Candida albicans. These tests have a sensitivity of >83% and a specificity of >97%, although false-positive results are common when prevalence is low.)
Imaging: No imaging indicated.
Special Tests: Vaginal pH 6 to 6.5 or higher.
Diagnostic Procedures: Physical examination, microscopic examination of vaginal secretions in normal saline (sensitivity of only approximately 60% to 70%).

Pathologic Findings

T. vaginalis is a fusiform protozoan, slightly larger than a white blood cell, with three to five flagella extending from the narrow end that provide active movement.

MANAGEMENT AND THERAPY

Nonpharmacologic

General Measures: Perineal hygiene, education regarding sexually transmitted infections.
Specific Measures: Medical therapy, vaginal acidification.
Diet: No specific dietary changes indicated. Avoid alcohol during metronidazole or tinidazole treatment.
Activity: Sexual continence until partner(s) are examined and treated.
Patient Education: American College of Obstetricians and Gynecologists Patient Education Pamphlet AP009 (How to Prevent Sexually Transmitted Diseases), AP028 (Vaginitis: Causes and Treatments). Patients should be advised to have all sexual partners seen for diagnosis and treatment.

Drug(s) of Choice

Metronidazole 2 g PO as a single dose or metronidazole 250 mg twice a day for 7 days. For recurrences where reinfection is excluded, metronidazole 500 mg PO twice a day for 7 days or tinidazole 2 g PO single dose.
Contraindications: Metronidazole is relatively contraindicated in the first trimester of pregnancy (pregnancy category B). Multiple studies and meta-analyses have not demonstrated a consistent association between metronidazole and teratogenic or mutagenic effects. Tinidazole is pregnancy category C.
Precautions: Metronidazole or tinidazole may produce a disulfiram-like reaction resulting in nausea, vomiting, headaches or other symptoms if the patient ingests alcohol. Patients should not use these agents if they have taken disulfiram in the preceding 2 weeks. Metronidazole must be used with care or the dose should be reduced in patients with hepatic disease.
Interactions: Metronidazole may potentiate the effects of warfarin or coumarin and alcohol (as noted earlier).

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Alternative Drugs

Tinidazole 2 g PO in a single dose. Topical clotrimazole, povidone iodine (topical), hypertonic (20%) saline douches. (Metronidazole gel is considerably less efficacious for the treatment of trichomoniasis (<50%) than oral preparations of metronidazole and should not be used.)

FOLLOW-UP

Patient Monitoring: Follow-up serologic testing for syphilis and human immunodeficiency virus (HIV) infection as indicated.
Prevention/Avoidance: Sexual monogamy, condom use for intercourse.
Possible Complications: Cystitis, infections of the Skene’s or Bartholin’s glands, increased risk of pelvic inflammatory disease (PID), pelvic pain, infertility, and other sequelae of sexually transmitted infections.
Expected Outcome: Resistance to metronidazole is uncommon (<5% with low-dose therapy, high-level resistance is rare). Most treatment failures are actually caused by reinfection or failure to comply with treatment.

MISCELLANEOUS

Pregnancy Considerations: Vaginal infections are associated with an increased risk of premature rupture of membranes, preterm delivery, and low birthweight. Data do not suggest that metronidazole treatment results in a reduction in perinatal morbidity. Discontinue breastfeeding during metronidazole treatment and for 12 to 24 hours after the last dose. While using tinidazole, discontinue breastfeeding during treatment and for 3 days after the last dose.
ICD-9-CM Codes: 131.0, 131.01 (Vaginal).

REFERENCES

Level I

Lossick JG. Single-dose metronidazole treatment for vaginal trichomoniasis. Obstet Gynecol. 1980;56:508.

Tidwell BH, Lushbaugh WB, Laughlin MD, et al. A double-blind placebo-controlled trial of single-dose intravaginal versus single-dose oral metronidazole in the treatment of trichomonal vaginitis. J Infect Dis. 1994;170:242.

Level II

Burtin P, Taddio A, Ariburnu O, et al. Safety of metronidazole in pregnancy: a meta-analysis. Obstet Gynecol. 1995;172:525.

Caro-Paton T, Carvajal A, Martin de Diego I, et al. Is metronidazole teratogenic? A meta-analysis. Br J Clin Pharmacol. 1997;44:179.

Forna F, Gulmezoglu AM. Interventions for treating trichomoniasis in women. Cochrane Database Syst Rev. 2, 2003. CD000218

Klebanoff MA, Carey JC, Hauth JC, et alNational Institute of Child Health, Human Development Network of Maternal-Fetal Medicine Units. Failure of metronidazole to prevent preterm delivery among pregnant women with asymptomatic Trichomonas vaginalis infection. N Engl J Med. 2001;345:487.

Okun N, Gronau KA, Hannah ME. Antibiotics for bacterial vaginosis or Trichomonas vaginalis in pregnancy: a systematic review. Obstet Gynecol. 2005;105:857.

Piper JM, Mitchel EF, Ray WA. Prenatal use of metronidazole and birth defects: no association. Obstet Gynecol. 1993;82:348.

Wiese W, Patel SR, Patel SC, et al. A meta-analysis of the Papanicolaou smear and wet mount for the diagnosis of vaginal trichomoniasis. Am J Med. 2000;108:301.

Level III

American College of Obstetricians and Gynecologists. Sexually transmitted diseases in adolescents. ACOG Committee Opinion 301. Washington, DC: ACOG, 2004.

American College of Obstetricians and Gynecologists, Vaginitis. ACOG Practice Bulletin 72 2006 ACOG Washington, DC Anderson MR, Klink K, Cohrssen A. Evaluation of vaginal complaints. JAMA. 2004;291:1368.

Centers for Disease Control and Prevention. Sexually transmitted diseases treatment guidelines, 2006. MMWR. 2006;55:52.

Eckert LO. Clinical practice. Acute vulvovaginitis. N Engl J Med. 2006;355:1244.

Eckert LO, Lentz GM. Infections of the lower genital tract. In: Katz VL, Lentz GM, Lobo RA, Gershenson DM, editors. Comprehensive Gynecology. 5th ed. Philadelphia: Mosby/Elsevier; 2007:591.

Lossick JG. Sexually transmitted vaginitis. Urol Clin North Am. 1984;11:141.

McLellan R, Spence MR, Brockman M, et al. The clinical diagnosis of trichomoniasis. Obstet Gynecol. 1982;60:30.

Moldwin RM. Sexually transmitted protozoal infections. Trichomonas vaginalis, Entamoeba histolytica, and Giardia lamblia. Urol Clin North Am. 1992;19:93.

Sobel JD. Vaginitis. N Engl J Med. 1997;337:1896.

Thomason JL, Gelbart SM. Trichomonas vaginalis. Obstet Gynecol. 1989;74:536.

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