Trichomoniasis
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INTRODUCTION
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Background: Trichomoniasis is a sexually
transmitted protozoal infection caused by Trichomonas vaginalis.
Women may be an asymptomatic carrier or experience a range of symptoms up to a
mild fulminant inflammatory disease. Its widespread
prevalence in the US and international
populations creates an important public health concern.
Pathophysiology: T vaginalis inhabits the vaginal
and urethral tissues. In women, T vaginalis is
isolated from the vagina, cervix, urethra, bladder, and Bartholin
and Skene glands. In men, the organism is isolated
from the anterior urethra, external genitalia, prostate, epididymis,
and semen. Symptoms typically occur after an incubation period of 4?8 days. The protozoan pathogen causes direct damage to the
epithelium, leading to microulcerations.
Frequency:
- In the US: Trichomoniasis affects 2-3 million women annually. The organism
also is detected in 30-40% of men who are exposed. The prevalence of T vaginalis infection at clinics treating sexually
transmitted diseases (STDs) varies between 8-31%. In men, trichomoniasis may account for as much as 17% of nongonococcal, non-chlamydial
urethritis.
- Internationally:
Trichomoniasis affects approximately 180
million women worldwide. The frequency in Europe is similar to
the US. In Africa, the prevalence
may be much higher. Trichomoniasis was present
in 65% of pregnant women attending an antenatal clinic in South Africa.
Mortality/Morbidity:
- Pregnant women
infected with T vaginalis are 30% more
likely than uninfected women to deliver preterm or to have a low birth
weight infant. They are also 40% more likely to deliver a preterm, low birthweight infant.
- Complications in
men include prostatitis, epididymitis,
urethral stricture disease, and infertility.
- T vaginalis infection is highly associated with the
presence of other STDs, such as gonorrhea, chlamydia,
and HIV. Coexisting symptomatic trichomoniasis
in men with HIV have a 6-fold increase in concentration of HIV in their
semen. Theoretically, this confers an increased risk of transmission to
their sexual partners.
Sex:
- Symptomatic trichomoniasis more commonly occurs in women.
- Trichomoniasis infection in men is less clinically apparent.
10-50% of the infected men may be asymptomatic carriers.
Age:
- Trichomoniasis is a STD; therefore, it is encountered in sexually
active adolescents and adults.
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CLINICAL
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History:
- Symptoms range from none in asymptomatic carriers to a severe pelvic
inflammatory disease.
- Common symptoms are yellow vaginal discharge, abnormal vaginal odor,
dyspareunia, and vulvar
itching.
- Some may experience dysuria.
- Symptoms range from none in asymptomatic carriers to urethritis complicated by prostatitis.
- The usual incubation period for the development of symptomatic
disease is 10 days or less.
- Nongonococcal urethritis
is the most typical clinical syndrome in symptomatic men.
- Discharge is present in 33-50% of symptomatic men and varies from
purulent to mucoid in character.
- Most
symptomatic infections are intermittent and self-limiting.
Physical:
- Purulent or
homogenous vaginal discharge, and vulvar or
vaginal erythema are common.
- The finding of colpitis macularis, or strawberry cervix, describes a diffuse
or patchy macular erythematous lesion of the
cervix. This is a specific sign for trichomoniasis,
but visible only 1-2% of the time without the aid of colposcopy.
With colposcopy, colpitis
macularis is detected in up to 45% of the
cases.
- Lower abdominal tenderness may be present; however, this is
described in less than 10% of the patients. If this occurs, the
possibility of a coexisting salpingitis or an
intra-abdominal pathology is evident.
- Coexisting infections with Neisseria
gonorrhea, candidiasis, and bacterial vaginosis are common and may produce a mixed clinical
picture.
- The physical
examination is generally unremarkable unless the infection is
complicated. It may be associated with local inflammatory states,
including balanitis and balanoposthitis.
- Physical findings of epididymitis and prostatitis also may occur.
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DIFFERENTIALS
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Bacterial vaginosis
Atrophic vaginitis with secondary infection
Erosive lichen planus
Foreign body vaginosis
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WORKUP
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Lab Studies:
- Laboratory
studies aid in the demonstration of the T vaginalis
organism and to differentiate the infection from other causes of vaginitis.
- Bedside
laboratory studies
- The vaginal pH measured on Nitrazine paper
is elevated.
- Usually, the pH is above 5.0 and may be as high as 6.0.
- Bacterial vaginosis or atrophic vaginitis also may cause elevation in the vaginal pH.
- The potassium hydroxide amine test reveals a fishy odor from the
application of 10% potassium hydroxide to a vaginal swab sample, which
suggests trichomoniasis and bacterial vaginosis.
- Saline
microscopic examination
- Obtaining a vaginal swab sample for saline wet mount evaluation is
an easy, valuable, and economical tool for obtaining diagnosis.
- Trichomonads, which are ovoid-shaped
parasites, are slightly larger than polymorphonuclear
lymphocytes (PMNs) and may be identified by
their ameboid mobility. Trichomonads
cause an inflammatory reaction; therefore, a large number of PMNs usually are present and this number correlates
with the severity of the infection.
- A saline wet prep is positive for identifying trichomonads
in approximately 60% of the cases.
- Trichomonads may be viewed on pap smears, but they only have a
sensitivity of 60-70% when compared to the use of saline microscopy.
- False-positive results are common with this technique.
- Incubate the cultures anaerobically.
- Growth is detected within 48 hours and has a sensitivity of 95%.
- Culture is important in the diagnosis of men, because the wet prep
is often negative.
- Polymerase chain
reaction
- Polymerase chain reaction (PCR) methods report high sensitivity and
specificity (97% and 98%, respectively).
- The
availability of this test may be limited.
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TREATMENT
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Medical Care:
- Systemic
treatment is important to ensure a cure, since trichomoniasis
is an infection of multiple sites (eg, vaginal
epithelium, Skene glands, Bartholin
glands, urethra).
- Oral metronidazole is the treatment of choice and is shown
in multiple studies to be superior in efficacy when compared to intravaginal treatment. Treatment failures may require
a high-dose metronidazole regimen.
Diet:
- Instruct the
patient to avoid alcohol while taking metronidazole,
because it may cause a disulfiram-like reaction.
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MEDICATION
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The 5-nitroimidazole group of drugs are
antiprotozoal effective agents, which are used for
the treatment of trichomoniasis. The mechanism of
action is not well understood; however, it is known that anaerobic organisms
preferentially reduce the 5-nitro group and active metabolites likely interact
with anaerobic bacterial and protozoal DNA.
Drug Category: Antiprotozoal agents -- Therapy must be comprehensive
and should cover all likely pathogens in the context of this clinical setting.
Drug
Name
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Metronidazole (Flagyl) -- This medication is available PO, IV,
and as intravaginal suppository gel. Highly
effective in the treatment of many anaerobic bacterial and protozoal infections.
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Adult
Dose
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250 mg PO tid qwk or 2 g PO one
time dose
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Pediatric
Dose
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15 mg/kg/d divided
tid qwk
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Contraindications
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Documented
hypersensitivity to the 5-nitroimidazole class of medications
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Interactions
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Inhibits
metabolism of warfarin and potentiates
the anticoagulant effect; causes an intolerance to alcohol similar to disulfiram; abdominal cramps, nausea, vomiting,
headaches, and flushing when co-ingested with alcohol; cimetidine
prolongs the plasma clearance by inhibiting metabolic enzymes; conversely,
drugs that induce liver enzymes (eg, phenobarbital) may increase the elimination of metronidazole
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Pregnancy
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B - Usually safe
but benefits must outweigh the risks.
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Precautions
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Usually well
tolerated; commonly encountered side effects are nausea, vomiting, anorexia,
and a metallic taste in the mouth; most serious side effects involve the
nervous system and are manifested as convulsions and peripheral neuropathy,
which are rare unless large doses are given for a prolonged period of time;
drug is slowly impaired in patients with reduced hepatic function; reduce
dose in patients with reduced hepatic function to prevent toxic levels from
building in the plasma
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FOLLOW-UP
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Further Outpatient Care:
- Sexual partners
must be treated to prevent reinfection.
- Consider empiric
treatment of other STDs that frequently coexist with trichomoniasis.
- Advise the patient to avoid intercourse until therapy is
complete and the patient and partner are asymptomatic.
- Persistent
treatment failures may require metronidazole
susceptibility testing through the Center for Disease Control (CDC).
Deterrence/Prevention:
- Condoms and oral
contraceptives may protect against transmission of trichomoniasis.
Complications:
- Please see
Morbidity section
Patient Education:
- Educate the
patient about STDs, including HIV, and methods of prevention.
- Discuss the side
effects and interactions encountered with metronidazole.
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MISCELLANEOUS
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Medical/Legal Pitfalls:
- Failure to treat
during pregnancy may result in an adverse fetal outcome.
- Screen for STDs
in the pregnant patient and treat appropriately.
Special Concerns:
- The use of metronidazole in the first trimester of pregnancy is
traditionally avoided because of concern over possible teratogenic
risk. Several studies, including a large meta-analysis of pregnant women
exposed to metronidazole in the first trimester,
found no increased risk of birth defects. Consider this when weighing the
benefits and any possible risk in treating pregnant patients.
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BIBLIOGRAPHY
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- Burtin P, Taddio A, Ariburnu O: Safety of metronidazole
in pregnancy: a meta-analysis. ALYSIS 1995 Feb; 172(2 Pt 1): 525-9[Medline].
- Cates W Jr: Estimates of the incidence and prevalence of
sexually transmitted diseases in the United States. American
Social Health Association Panel. Sex Transm Dis 1999 Apr; 26(4 Suppl):
S2-7[Medline].
- Cotch MF, Pastorek JG 2nd, Nugent RP: Trichomonas vaginalis associated with low birth weight and preterm
delivery. The Vaginal Infections and Prematurity
Study Group [see comments]. Sex Transm Dis 1997 Jul; 24(6): 353-60[Medline].
- Haefner HK: Current evaluation and management of vulvovaginitis. Clin Obstet Gynecol 1999 Jun;
42(2): 184-95[Medline].
- Hammill HA: Trichomonas vaginalis. Obstet Gynecol Clin North Am 1989
Sep; 16(3): 531-40[Medline].
- Krieger JN: Trichomoniasis in men: old issues and new data. Sex Transm Dis 1995 Mar-Apr;
22(2): 83-96[Medline].
- Madico G, Quinn TC, Rompalo A:
Diagnosis of Trichomonas vaginalis
infection by PCR using vaginal swab samples. J Clin
Microbiol 1998 Nov; 36(11): 3205-10[Medline].
- Redondo-Lopez V,
Meriwether C, Schmitt C: Vulvovaginal candidiasis complicating recurrent bacterial vaginosis. Sex Transm Dis 1990 Jan-Mar; 17(1): 51-3[Medline].
- Saurina GR, McCormack WM: Trichomoniasis
in pregnancy [editorial; comment]. Sex Transm Dis 1997 Jul; 24(6): 361-2[Medline].
- Sobel JD: Vaginitis [see
comments]. N Engl J Med 1997 Dec
25; 337(26): 1896-903[Medline].
- Sobel JD: Vaginal infections in adult women. Med Clin North Am 1990 Nov; 74(6): 1573-602[Medline].
- Wolner-Hanssen P, Krieger JN, Stevens CE: Clinical manifestations
of vaginal trichomoniasis. JAMA 1989 Jan 27;
261(4): 571-6[Medline].
NOTE:
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Medicine is a
constantly changing science and not all therapies are clearly established.
New research changes drug and treatment therapies daily. The authors,
editors, and publisher of this journal have used their best efforts to
provide information that is up-to-date and accurate and is generally accepted
within medical standards at the time of publication. However, as medical
science is constantly changing and human error is always possible, the
authors, editors, and publisher or any other party involved with the
publication of this article do not warrant the information in this article is
accurate or complete, nor are they responsible for omissions or errors in the
article or for the results of using this information. The reader should
confirm the information in this article from other sources prior to use. In
particular, all drug doses, indications, and contraindications should be
confirmed in the package insert. FULL DISCLAIMER
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