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Trichomonas vaginalis

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Title: Trichomonas vaginalis  
Author: World Heritage Encyclopedia
Language: English
Subject: Trichomoniasis, Sexually transmitted infection, Cervicitis, Vaginitis, Giardia lamblia
Collection: Eukaryotes with Sequenced Genomes, Metamonads, Parasites of Humans, Sexually Transmitted Diseases and Infections
Publisher: World Heritage Encyclopedia

Trichomonas vaginalis

Trichomonas vaginalis
T. vaginalis phase contrast microscopy
Scientific classification
Domain: Eukarya
Phylum: Metamonada
Class: Parabasalia
Order: Trichomonadida
Genus: Trichomonas
Species: T. vaginalis
Binomial name
Trichomonas vaginalis
(Donné 1836)
Trichomonas vaginalis

is an anaerobic, flagellated protozoan parasite and the causative agent of trichomoniasis. It is the most common pathogenic protozoan infection of humans in industrialized countries.[1] Infection rates between men and women are similar with women being symptomatic, while infections in men are usually asymptomatic. Transmission usually occurs via direct, skin-to-skin contact with an infected individual, most often through vaginal intercourse. The WHO has estimated that 160 million cases of infection are acquired annually worldwide.[2] The estimates for North America alone are between 5 and 8 million new infections each year, with an estimated rate of asymptomatic cases as high as 50%.[3] Usually treatment consists of metronidazole and tinidazole.[4]


  • Clinical 1
    • Mechanism of infection 1.1
    • Symptoms 1.2
    • Signs 1.3
    • Complications 1.4
    • Diagnosis 1.5
    • Treatment 1.6
  • Morphology 2
  • Protein function 3
  • Virulence factors 4
  • Genome sequencing and statistics 5
  • Increased susceptibility to HIV 6
  • Evolution 7
  • See also 8
  • Further Reading 9
  • References 10
  • External links 11


Mechanism of infection

Trichomonas vaginalis, a parasitic protozoan, is the etiologic agent of trichomoniasis, and is a sexually transmitted infection.[2][5] More than 160 million people worldwide are annually infected by this protozoan.[2]


Pap smear, showing infestation by Trichomonas vaginalis. Papanicolaou stain, 400x

, a sexually transmitted infection of the urogenital tract, is a common cause of vaginitis in women, while men with this infection can display symptoms of urethritis. 'Frothy', greenish vaginal discharge with a 'musty' malodorous smell is characteristic.[6]


Only 2% of women with the infection will have a "strawberry" cervix (colpitis macularis, an erythematous cervix with pinpoint areas of exudation) or vagina on examination.[7][8][9] This is due to capillary dilation as a result of the inflammatory response.


Some of the complications of T. vaginalis in women include: preterm delivery, low birth weight, and increased mortality as well as predisposing to HIV infection, AIDS, and cervical cancer.[10] T. vaginalis has also been reported in the urinary tract, fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Condoms are effective at reducing, but not wholly preventing, transmission.[11]

T. vaginalis infection in males has been found to cause asymptomatic urethritis and prostatitis.[12] It has been proposed that it may increase the risk of prostate cancer; however, evidence is insufficient to support this association as of 2014.[12]


Classically, with a cervical smear, infected women have a transparent "halo" around their superficial cell nucleus.[13] It is unreliably detected by studying a genital discharge or with a cervical smear because of their low sensitivity. T. vaginalis was traditionally diagnosed via a wet mount, in which "corkscrew" motility was observed. Currently, the most common method of diagnosis is via overnight culture,[14][15] with a sensitivity range of 75-95%.[16] Newer methods, such as rapid antigen testing and transcription-mediated amplification, have even greater sensitivity, but are not in widespread use.[16] The presence of T. vaginalis can also be diagnosed by PCR, using primers specific for GENBANK/L23861.[17]


Infection is treated and cured with metronidazole[18] or tinidazole. Metronidazole would normally be prescribed for a 7 day period and Tinidazole as a two day course, which appears to have a higher success rate than the single dose option. Medication should be prescribed to any sexual partner(s) as well because they may be asymptomatic carriers.[6][19]


Unlike other parasitic protozoa (axostyle projects opposite the four-flagella bundle. The axostyle may be used for attachment to surfaces and may also cause the tissue damage seen in trichomoniasis infections.[20]

While T. vaginalis does not have a cyst form, organisms can survive for up to 24 hours in urine, semen, or even water samples.

Protein function

T. vaginalis lacks mitochondria and therefore necessary enzymes and cytochromes to conduct hydrogenosome.[21]

Virulence factors

One of the hallmark features of Trichomonas vaginalis is the adherence factors that allow cervicovaginal epithelium colonization in women. The adherence that this organism illustrates is specific to vaginal epithelial cells (VECs) being pH, time and temperature dependent. A variety of virulence factors mediate this process some of which are the microtubules, microfilaments, adhesins (4), and cysteine proteinases. The adhesins are four trichomonad enzymes called AP65, AP51, AP33, and AP23 that mediate the interaction of the parasite to the receptor molecules on VECs.[22] Cysteine proteinases may be another virulence factor because not only do these 30 kDa proteins bind to host cell surfaces but also may degrade extracellular matrix proteins like hemoglobin, fibronectin or collagen IV.[23]

Genome sequencing and statistics

The T. vaginalis genome was found to be approximately 160 megabases in size[24] – ten times larger than predicted from earlier gel-based chromosome sizing [25] (The human genome is ~3.5 gigabases by comparison.[26]) As much as two-thirds of the T. vaginalis sequence consists of repetitive and transposable elements, reflecting a massive, evolutionarily recent expansion of the genome. The total number of predicted protein-coding genes is ~98,000, which includes ~38,000 'repeat' genes (virus-like, transposon-like, retrotransposon-like, and unclassified repeats, all with high copy number and low polymorphism). Approximately 26,000 of the protein-coding genes have been classed as 'evidence-supported' (similar either to known proteins, or to ESTs), while the remainder have no known function. These extraordinary genome statistics are likely to change downward as the genome sequence, currently very fragmented due to the difficulty of ordering repetitive DNA, is assembled into chromosomes, and as more transcription data (ESTs, microarrays) accumulate. But it appears that the gene number of the single-celled parasite T. vaginalis is, at minimum, on par with that of its host H. sapiens.

In late 2007 was launched as a free, public genomic data repository and retrieval service devoted to genome-scale trichomonad data. The site currently contains all of the T. vaginalis sequence project data, several EST libraries, and tools for data mining and display. TrichDB is part of the NIH/NIAID-funded EupathDB functional genomics database project.[27]

Increased susceptibility to HIV

The damage caused by Trichomonas vaginalis to the vaginal epithelium increases a woman's susceptibility to an HIV infection. In addition to inflammation, the parasite also causes lysis of epithelial cells and RBCs in the area leading to more inflammation and disruption of the protective barrier usually provided by the epithelium. Having Trichomonas vaginalis also may increase the chances of the infected woman transmitting HIV to her sexual partner(s).[28][29]


The biology of T. vaginalis has implications for understanding the origin of sexual reproduction in eukaryotes. T. vaginalis is not known to undergo Giardia lamblia (also called Giardia intestinalis), indicating that these meiotic genes were present in a common ancestor of T. vaginalis and G. intestinalis. Since these two species are descendants of lineages that are highly divergent among eukaryotes, Malik et al.[30] noted that these meiotic genes were likely present in a common ancestor of all eukaryotes.

See also

Further Reading

Hernández, Hilda M.; Marcet, Ricardo; Sarracent, Jorge (28 October 2014). "Biological roles of cysteine proteinases in the pathogenesis of Trichomonas vaginalis". Parasite 21 (54): 1-10. doi:10.1051/parasite/2014054. PMID 25348828. Retrieved 10 February 2015. [31]


  1. ^ Soper, D (2004). "Trichomoniasis: under control or undercontrolled?". American Journal of Obstetrics and Gynecology 190 (1): 281–90.  
  2. ^ a b c Harp, Djana F.; Chowdhury, Indrajit (2011). "Trichomoniasis: Evaluation to execution". European Journal of Obstetrics & Gynecology and Reproductive Biology 157 (1): 3–9.  
  3. ^ Hook, Edward W. (1999). "Trichomonas vaginalis—No Longer a Minor STD". Sexually Transmitted Diseases 26 (7): 388–9.  
  4. ^ W Evan Secor. "Trichomonas Vaginalis". MedScape. 
  5. ^ Johnston VJ, Mabey DC (February 2008). "Global epidemiology and control of Trichomonas vaginalis". Current Opinion in Infectious Diseases 21 (1): 56–64.  
  6. ^ a b Nanda, N; Michel, RG; Kurdgelashvili, G; Wendel, KA (2006). "Trichomoniasis and its treatment". Expert review of anti-infective therapy 4 (1): 125–35.  
  7. ^ Swygard H, Seña AC, Hobbs MM, Cohen MS (April 2004). "Trichomoniasis: clinical manifestations, diagnosis and management". Sex Transm Infect 80 (2): 91–5.  
  8. ^ Petrin D, Delgaty K, Bhatt R, Garber G (April 1998). "Trichomonas vaginalis"Clinical and microbiological aspects of . Clin. Microbiol. Rev. 11 (2): 300–17.  
  9. ^ Garber GE (January 2005). "Trichomonas vaginalis"The laboratory diagnosis of . Can J Infect Dis Med Microbiol 16 (1): 35–8.  
  10. ^ Schwebke, J. R.; Burgess, D. (2004). "Trichomoniasis". Clinical Microbiology Reviews 17 (4): 794–803, table of contents.  
  11. ^ "Trichomoniasis". CDC Fact Sheet. Centers for Disease Control and Prevention. 2007-12-17. Retrieved 2010-06-11. 
  12. ^ a b Caini, Saverio; Gandini, Sara; Dudas, Maria; Bremer, Viviane; Severi, Ettore; Gherasim, Alin (2014). "Sexually transmitted infections and prostate cancer risk: A systematic review and meta-analysis". Cancer Epidemiology 38 (4): 329–338.  
  13. ^ Avwioro O G. "Diagnosis of trichomoniasis in pap smears; How effective is it?". European Journal of Experimental Biology (Pelagia Research Library) 1 (1): 10–13. 
  14. ^ Ohlemeyer, C; Hornberger, L; Lynch, D; Swierkosz, E (March 1998). "Diagnosis of Trichomonas vaginalis in adolescent females: InPouch TV® culture versus wet-mount microscopy". Journal of Adolescent Health 22 (3): 205–8.  
  15. ^ Sood, Seema; Mohanty, Srujana; Kapil, Arti; Tolosa, Jorge; Mittal, Suneeta (2007). "Trichomonas vaginalis"InPouch TV culture for detection of (PDF). The Indian journal of medical research 125 (4): 567–71.  
  16. ^ a b Huppert, Jill S.; Mortensen, Joel E.; Reed, Jennifer L.; Kahn, Jessica A.; Rich, Kimberly D.; Miller, William C.; Hobbs, Marcia M. (2007). "Rapid Antigen Testing Compares Favorably with Transcription‐Mediated Amplification Assay for the Detection of Trichomonas vaginalis in Young Women". Clinical Infectious Diseases 45 (2): 194–8.  
  17. ^ Schirm, Jurjen; Bos, Petra A.J.; Roozeboom-Roelfsema, Irene K.; Luijt, Dirk S.; Möller, Lieke V. (2007). "Trichomonas vaginalis detection using real-time TaqMan PCR". Journal of Microbiological Methods 68 (2): 243–7.  
    repeated DNA target for PCR identification"Trichomonas vaginalis". GenBank Nucleotide Database. National Center for Biotechnology Information. L23861.1. 
    Kengne P, Veas F, Vidal N, Rey JL, Cuny G (September 1994). "Trichomonas vaginalis: repeated DNA target for highly sensitive and specific polymerase chain reaction diagnosis". Cell. Mol. Biol. (Noisy-le-grand) 40 (6): 819–31.  
  18. ^ "Metronidazole". HealthExpress. Retrieved 31 July 2013. 
  19. ^ Cudmore, S. L.; Delgaty, K. L.; Hayward-Mcclelland, S. F.; Petrin, D. P.; Garber, G. E. (2004). "Trichomonas vaginalis"Treatment of Infections Caused by Metronidazole-Resistant . Clinical Microbiology Reviews 17 (4): 783–93, table of contents.  
  20. ^ Ryan, Kenneth James; Ray, C. George; Sherris, John C., eds. (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill.  
  21. ^ Upcroft, P.; Upcroft, J. A. (2001). "Drug Targets and Mechanisms of Resistance in the Anaerobic Protozoa". Clinical Microbiology Reviews 14 (1): 150–64.  
  22. ^ Arroyo, R.; Engbring, J.; Alderete, J. F. (1992). "Molecular basis of host epithelial cell recognition by Trichomonas vaginalis". Molecular Microbiology 6 (7): 853–862.  
  23. ^ Mendoza-Lopez, M. R.; Becerril-Garcia, C.; Fattel-Facenda, L. V.; Avila-Gonzalez, L.; Ruiz-Tachiquin, M. E.; Ortega-Lopez, J.; Arroyo, R. (2000). Cytoadherence"Trichomonas vaginalis"CP30, a Cysteine Proteinase Involved in . Infection and Immunity 68 (9): 4907–12.  
  24. ^ Carlton, J. M.; Hirt, R. P.; Silva, J. C.; Delcher, A. L.; Schatz, M.; Zhao, Q.; Wortman, J. R.; Bidwell, S. L.; et al. (2007). "Trichomonas vaginalis"Draft Genome Sequence of the Sexually Transmitted Pathogen . Science 315 (5809): 207–12.  
  25. ^ Lehker, M. W.; Alderete, J. F. (1999). "Resolution of Six Chromosomes of Trichomonas vaginalis and Conservation of Size and Number among Isolates". The Journal of Parasitology 85 (5): 976–9.  
  26. ^ Zimmer, C. (2007). "EVOLUTION: Jurassic Genome". Science 315 (5817): 1358–9.  
  27. ^ Aurrecoechea, Cristina; Brestelli, John; Brunk, Brian P.; Carlton, Jane M.; Dommer, Jennifer; Fischer, Steve; Gajria, Bindu; Gao, Xin; et al. (2009). "Trichomonas vaginalis and Giardia lamblia"GiardiaDB and TrichDB: integrated genomic resources for the eukaryotic protist pathogens . Nucleic Acids Research 37 (Database issue): D526–30.  
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  29. ^ Mavedzenge, Sue Napierala; Van der Pol, Barbara; Cheng, Helen; Montgomery, Elizabeth T.; Blanchard, Kelly; de Bruyn, Guy; Ramjee, Gita; Van der Straten, Ariane (2010). "Epidemiological Synergy of Trichomonas vaginalis and HIV in Zimbabwean and South African Women". Sexually Transmitted Diseases 37 (7): 460–6.  
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  31. ^ Hernández, Hilda M.; Marcet, Ricardo; Sarracent, Jorge (28 October 2014). "Biological roles of cysteine proteinases in the pathogenesis of Trichomonas vaginalis" (PDF). Parasite 21 (54): 1-10.  

External links

  • TIGR's Trichomonas vaginalis genome sequencing project.
  • genome resourceTrichomonas vaginalisTrichDB: the
  • NIH site on trichomoniasis.
  • Taxonomy
  • STI: What's trichomonas a website for teenagers
  • eMedicine article on trichomoniasis.
  • Trichomonas vaginalis at the Encyclopedia of Life
  • Patient UK
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