Trichomoniasis

Pathophysiology:

T vaginalis principally infects the squamous epithelium of the genital tract. Incubation time is generally between 4 and 28 days. Infection may persist for long periods in females, but generally persists less than 10 days in males. Anecdotal evidence suggests that asymptomatic infection may persist for months or even years in women.

In females, vaginitis is the most common manifestation of infection. Other complications include infection of the adnexa, endometrium, and Skene and Bartholin glands. Males are usually asymptomatic. When symptoms are present, they usually manifest as urethritis. Up to 11% of nongonococcal urethritis cases are caused by T vaginalis. Other complications include infection of the prostate, foreskin, glans, and epididymis.

Infection with T vaginalis is a marker of high-risk sexual behavior. Co-infection with other STDs is common. In one study of adolescents who had a diagnosis of at least one STD, there was almost a 9-fold increase in the likelihood of T vaginalis infection in the ensuing 3 months.

Infection produces immunity that at best is only partially protective. Evidence of lymphocyte priming is shown by the presence of antigen-specific peripheral blood mononuclear cells. An antibody response locally and in serum has also been detected. Despite the interaction that the human immune system has with T vaginalis, little evidence exists that it prevents infection. One study showed no association between trichomoniasis and the use of protease inhibitors or immune status in women with HIV. Another study showed that HIV seropositivity does not alter the rate of infection.


Vertical transmission of T vaginalis during birth is possible and may persist up to 1 year. From 2 to 17% of female offspring of infected women acquire infection.


Nitroimidazoles are a class of drugs used to fight a variety of parasitic and anaerobic bacterial infections. The drug is taken up by target organisms and reduced to its active form. The reduced drug then disrupts the helical structure of the DNA within these microbes preventing nucleic acid synthesis and eventually leading to cell death.


Metronidazole (Flagyl) -- Active against various anaerobic bacteria and protozoa; mode of action not well understood; appears to be absorbed into cells; intermediate-metabolized compounds formed bind DNA and inhibit protein synthesis, causing cell death.
Metronidazole is treatment of choice.
Single-dose therapy with 2 g PO is as effective as prolonged therapy with 500 mg bid for 7 d.
Single-dose therapy increases compliance.
Metronidazole gel is effective in less than half the cases of trichomoniasis.
Now reports of resistance to metronidazole approaching 5-10% exist.
If treatment with either single-dose or multi-dose therapy fails, patient should be treated with 500 mg PO bid for 7 d. If this fails, patient should take 2 g PO qd for 3-5 d

Category: Gynecology Notes