Human Immunodeficiency Virus (HIV)

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T. vaginalis as Risk Factor for HIV Transmission Among Both Sexes

The association of sexually transmitted diseases (STDs) and human immunodeficiency virus type 1 (HIV-1) transmission has received much attention over the past 10 years. STDs are a potential cofactor for the transmission of HIV-1 by increasing the susceptibility of the uninfected partner as well as the infectivity of an infected individual.

Trichomoniasis Association with Increased HIV Shedding in Females

Metronidazole Treatment Effect on Vaginal
HIV-1 RNA in Women with T. vaginalis3

Bar graph showing the effect of metronidazole treatment on HIV-1 RNA vaginal concentrations in women infected with Trichomonas vaginalis. Concentrations of HIV RNA per swab before and after treatment were 4,677 and 1,122, respectively.

Several studies have shown that T. vaginalis infection is associated with increased risk of HIV infectivity and transmission. T. vaginalis may amplify HIV-1 transmission by increasing both susceptibility in an HIV-1 negative person and the infectiousness in an HIV-1 positive patient.1

Coinfection of T. vaginalis and HIV may increase HIV vaginal shedding, and treatment of trichomoniasis may reduce vaginal shedding. In a 1993 case control study of 431 initially HIV-negative women, after a 2 year prospective follow up, infection with trichomoniasis was independently associated with HIV seroconversion.2

A 2001 study reported that treatment of trichomoniasis with a 10-day course of metronidazole resulted in a 4.2-fold reduction in mean HIV-1 virus in vaginal secretions.3

Association with HIV Concentrations in Semen of Men

The association of trichomoniasis with HIV amplification is seen among men as well. A 1999 study determined the prevalence of Trichomonas in Malawian men with and without urethritis and examined the effect of Trichomonas infection on excretion of HIV in semen. This study also determined the overall prevalence of HIV in this population (51%). Trichomonas was detected in 38 of 293 men (13%) and it was the second most common pathogen in men with symptomatic urethritis. The prevalence of trichomoniasis among symptomatic men was 15.7%, and among asymptomatic men it was 8.7%. HIV seropositive men with symptomatic urethritis and Trichomonas had a six-fold higher concentration of HIV RNA in semen than HIV-positive men with urethritis in the absence of trichomoniasis.4

HIV RNA Concentrations in Semen of
Men with Symptomatic Urethritis4

Bar graph comparing the concentrations of HIV RNA found in the semen of men who have trichomononiasis and men who do not. In T. vaginalis positive men, the concentration of HIV RNA was 3.45 times 10 to the 5th copies per milliliter. In T. vaginalis negative men, the concentration was 5 times 10 to the 3rd copies per milliliter.

A 2003 study of Malawian men looked at the impact of treatment with 2g metronidazole or placebo in addition to standard urethritis treatment (gentamicin and doxycycline), on the effects of T. vaginalis treatment, signs and symptoms of urethritis and on concentrations of HIV in semen among dually infected men. Among the subset of HIV-infected men with trichomoniasis treated with metronidazole, post-treatment, the seminal plasma HIV RNA concentration was lower than in a group of HIV-positive controls.5

  1. Sorvillo F, Smith L, Kerndt P, Ash L. Trichomonas vaginalis, HIV, and African-Americans. Emerg Infect Dis. 2001 Nov-Dec;7(6):927-32.
  2. Laga M, Manoka A, Kivuvu M, Malele B, Tuliza M, Nzila N, Goeman J, Behets F, Batter V, Alary M. Non-ulcerative sexually transmitted diseases as risk factors for HIV-1 transmission in women: results from a cohort study. AIDS. 1993 Jan;7(1):95-102.
  3. Wang CC, McClelland RS, Reilly M, Overbaugh J, Emery SR, Mandaliya K, Chohan B, Ndinya-Achola J, Bwayo J, Kreiss JK. The effect of treatment of vaginal infections on shedding of human immunodeficiency virus type 1. J Infect Dis. 2001 Apr 1;183(7):1017-22. Epub 2001 Feb 28.
  4. Hobbs MM, Kazembe P, Reed AW, Miller WC, Nkata E, Zimba D, Daly CC, Chakraborty H, Cohen MS, Hoffman I. Trichomonas vaginalis as a cause of urethritis in Malawian men. Sex Transm Dis. 1999 Aug;26(7):381-7.
  5. Price MA, Zimba D, Hoffman IF, Kaydos-Daniels SC, Miller WC, Martinson F, Chilongozi D, Kip E, Msowoya E, Hobbs MM, Kazembe PN, Cohen MS. Addition of treatment for trichomoniasis to syndromic management of urethritis in Malawi: a randomized clinical trial. Sex Transm Dis. 2003 Jun;30(6):516-22.