Sexually Transmitted Infections

Formerly called venereal diseases (after Venus, the god of love), sexually transmitted infections (STIs) infect more than 1 million people every day, with approximately 500 million individuals infected at any given time with the four main curable STIs (chlamydia, gonorrhoea, syphilis and trichomoniasis)[2]. While not every exposure will lead to infection, and many can be cured (blood-borne viral infections can often only be suppressed), sexually-transmitted infections produce massive physical, social, mental, psychological and spiritual disabilities which in severe instances may lead to a loss of livelihood and death.

Estimated numbers of new cases of chlamydia, gonorrhoea, syphilis and trichomoniasis in 2008[2].

 STIs rank among the top five disease categories for which adults seek health care, despite the continuing efforts of advocacy, education, counseling, and interventions to assist vulnerable populations (adolescents, sex workers, the poor and uneducated, homosexual males, prison inmates, mobile populations and intravenous drug users)[2]. Challenging factors include the natural human state of sexual promiscuity, limited resources, stigmatisation (treatment not sought out of embarrassment/fear), poor quality of services and poor notification strategies (informing potentially-infected sexual partners) in these vulnerable populations[2].

In addition to reducing unintended pregnancies, some contraceptive devices (usually barrier methods such as condoms) may protect against certain infectious diseases which are commonly spread through sexual forms of contact. Pathogens (disease-causing organisms) must either enter and colonise the soft, ‘wet’, ‘fleshy’ tissues of the internal mucosal membranes (all non-skin coverings, such as around the eyes, nasal passage, mouth, throat, penis, vagina and anus) or penetrate the tough layers of the skin (such as in cuts, tears, burns and needle injection/injury) to reach the underlying tissue[1]. Those particularly at risk following sexual contact include those already infected with another STI (particularly HIV or gonorrhoea), those with ineffective immune systems (genetic disorders, cancer, chronic infection or stress), the malnutritioned (poor nourishment), the very young (immature immune system) and the elderly (disintegrating immune system)[1].

 As many STIs do not produce obvious symptoms in many people, they may still cause tissue damage and may be passed unknowingly on to future sexual partners or to unborn foetuses; regular STI screening is advisable, particularly following risky behaviour and/or the development of symptoms. During treatment of any STI, sexual activity should be avoided until the completion of the full course of treatment, and any sexual partners should also undergo treatment to prevent recurrence or spread of infection.

Two of the most common STIs are introduced below; bacterial STIs can additionally be found here and viral STIs here.

Trichmoniasis

Trichomonas vaginalis. Source:
http://www.phsource.us/PH/HELM/PH_Images_Parasites/Trichomonas%20vaginalis2.jpg

Trichomonas vaginalis is a protozoan parasite (see image on right)which produces the world’s most common STI, Trichomoniasis (≈200 million people are infected worldwide with ≈300 million new cases each year)[2]. This inhabits the male and female reproductive systems, producing irritation of the vagina (females only, of course) and urethra. In females this produces a profuse, foamy, creamy-yellow, fishy-smelling discharge which may cause irritation of the vulva (makes walking and sitting difficult) or a burning pain during urination and sex[1,2,3,4]. While symptoms are rare (fewer than 20% experience symptoms), it is extremely infectious, with a 100% transmission rate from male to female during sexual intercourse[2,3]. Infection during pregnancy may promote premature delivery, which is associated with a range of effects to the child[1,2].

Infection almost always occurs during sexual activity, as it can only survive outside the host for a few hours. Nevertheless, towels, washcloths and underwear should not be shared as these can carry infectious (viable) protozoans[4]. Risk factors for exposure include poverty, poor education and ethnicity (minority groups have higher rates due to limited healthcare access) douching and concurrent chlamydial/gonorrhoeal infection (as it reduces protective microflora from the vagina), sexual promiscuity (80% infection in prostitutes), marijuana use, having sexual partners more than five years older and age (markedly higher in those 16-35 years of age probably due to limited education and sexual promiscuity)[3,4]. Detection involves taking a sample of the vaginal discharge, or of a swab from the tip of the penis or within the vagina (testing for Trichomonas is not typically done, so one may need to mention it to their GP if suspicious)[4]. Treatment uses the antibiotic Metronidazole, which is taken with food (and during the course of treatment both sexual activity and alcohol must be avoided, as alcohol interferes with the activity of Metronidazole)[1,4].

Thrush

Candidiasis (thrush) is an extremely common fungal infection caused by (mostly) Candida albicans. Producing painful irritation of the genitalia (usually the vulva and vagina in females), it may also infect the mouth, throat (see image below) and anus[1,5]. Other symptoms include a white and cheesy discharge with a thick yeasty smell, burning pain during urination and sexual activity, and itchy, swollen and red genitals[1,5].

Oropharyngeal candidiasis. Source:
http://hardinmd.lib.uiowa.edu/pictures22/cdc/6053_067_lores.jpg

Risk factors include pregnancy, the use of contraceptive pills or certain steroids, the use of certain antibiotics or vaginal soaps (kills normal, 'good' bacteria, thereby allowing Candida to grow), wearing tight and synthetic underwear (produces a moist enivronment), poorly controlled diabetes (readily-available glucose encourages fungal growth), and having a suppressed immune system (chemotherapy, chronic stress or AIDS)[5].
 

Detection requires a simple examination of the genitals and a swab of the affected area, where the fungus is cultured and analysed[5]. Treatment uses topical Azole creams (available from the local pharmacy) to the affected area, and sex should be avoided during treatment[1,5]. Some resistant strains may require a longer course of more potent antifungals. Interestingly, while natural yoghurt may soothe the area, it will not cure thrush (and may actually encourage growth)[5].

References

1. Willey JM, Sherwood LM, Woolverton CJ. Prescott's Microbiology. 8th ed. Singapore: McGraw-Hill; 2011.
2. World Health Organisation. Global incidence and prevalence of selected curable sexually transmitted infections – 2008 Geneva: World Health Organization, Department of Reproductive Health and Research; 2012. Available from: http://www.who.int/reproductivehealth/publications/rtis/stisestimates/en/index.html [Accessed 30 Mar 2014].
3. Krashin JW, Koumans EH, Bradshaw-Sydnor AC, Braxton JR, Evan Secor W, Sawyer MK, et. al. Trichomonas vaginalis prevalence, incidence, risk factors and antibiotic-resistance in an adolescent population. Sex Transm Dis. 2010 Jul;37(7):440-4.
4. Department of Health (WA). Trichomoniasis Fact Sheet [Internet]. Perth, WA (Australia): Department of Health (WA); 2012 [cited 2014 Mar 25]. Available from: http://www.public.health.wa.gov.au/2/418/2/trichomoniasis_fact_sheet.pm.
5. Department of Health (WA). Thursh Fact Sheet [Internet]. Perth, WA (Australia): Department of Health (WA); 2008 [cited 2014 Mar 25]. Available from: http://www.public.health.wa.gov.au/2/417/2/thrush_fact_sheet.pm.