Chapter 25. Sexually Transmitted Diseases in Women Who Have Sex with Women

• • Transmission of common sexually transmitted diseases (STDs), including trichomoniasis and human papillomavirus (HPV), has been reported in women who have sex with women (WSW).
• • Transmission likely is mediated through exchange of infected cervicovaginal secretions or direct contact.
• • Most WSW, including self-defined lesbians, have had sex with men.
• • Barriers to care exist for many WSW, including lack of provider education about relevant issues.
• • Papanicolaou (Pap) smear screening should be performed in WSW according to routine national guidelines.

Relatively few data are available to inform estimates of the risk of female-to-female sexual transmission of STDs. The available data come primarily from four sources.

First, review of records from clinics that provide STD services (STD clinics) has provided estimates of some outcomes, including diagnosis of STD syndromes, laboratory results, and risk reporters. Such studies have the advantages of capturing a reproducible population of women who can be characterized relative to heterosexual women attending the same venue and of relying on clinician-based or laboratory-defined reports of outcomes, but are limited primarily by the relatively small number of WSW who attend these clinics.

Second, several studies have recruited women who either self-identify as lesbian or who report recent same-sex behavior, regardless of stated identity. Although this type of study may capture a more representative sample of WSW and frequently includes laboratory diagnosis of STDs, the sample of women included is likely biased due to self-selection for enrollment.

Third, although population-based surveys attempt to enroll a more representative sample of women, including WSW, because these surveys are generally expensive and complex to undertake, most do not include laboratory-confirmed assessment of STDs but rely on self-reported STD history.

Finally, case reports of STD transmission between women provide the only documented evidence available for some STDs. Despite their obvious limitations, these reports are valuable in that they can demonstrate the potential for STD transmission between women and, as such, help to emphasize the need for more robust, population-based data to inform WSW patients and their providers about the true risks associated with same-sex behavior between women.

Numerous studies have demonstrated that important barriers to health care exist for WSW. These barriers include, but are not limited to, lack of patient educational materials aimed at their specific risks and circumstances, lack of knowledge among providers, low socioeconomic status, absence of spousal benefits, and impact of negative experiences within the health care system. Among the latter are included outright instances of homophobia and general invisibility. For example, many office registration materials still list options for marital status as “single” or “married”—terms that do not apply to WSW who may be in domestic partnerships, particularly those that are not recognized by regulatory authorities. Even providers who are comfortable assessing STD-related risks may not be knowledgeable about the sexual practices engaged in by many WSW, or about the limited disease-specific information in the literature. For these reasons, education of providers in this area is paramount.

Because recent national surveys indicate that same-sex behavior among women is relatively common, providers should familiarize themselves with information about this patient population, and be aware of referral options for more detailed information. Available information on transmission of specific STDs in WSW is discussed later, under Laboratory Studies.

Risk Assessment

Risk assessment in WSW should begin the way all STD-related risk assessment begins in every patient: with a thorough sexual history. Most importantly, providers should not make assumptions about sexual practices based on the patient’s self-reported identity—in this case, specifically, as a lesbian. Assuming that a self-identified lesbian has not previously been or is not currently sexually active with men is usually incorrect. In one study, 74% of self-identified lesbians had male partners in the past, and of self-identified bisexual women, 98% had prior or current male partners. Among lesbians recruited for studies in Seattle, 80–86% reported prior sex with men, 23–28% had had sex with a man in the last year, and the median number of male and female lifetime partners was the same. In a sample of women evaluated at a London STD clinic, 69% of those identifying as lesbian had prior male partners, and at another London clinic specializing in the sexual health of lesbians, 91% had prior male partners. Heterosexual intercourse transmits the full range of STDs, some of which (notably, chronic viral infections, including HPV, genital herpes, hepatitis B virus, and HIV) may remain undetected for years.

Important components of the sexual history include number of recent (prior 2 months and 1 year) and lifetime sexual partners, both male and female. Other key components should include types of sexual practices that could pose a risk of transmission of STDs. Some sexual practices—including oral-genital sex; vaginal or anal sex using hands, fingers, or penetrative sex toys; and oral-anal sex—are practiced commonly between female sex partners. Practices involving digital-vaginal or digital-anal contact, particularly with shared penetrative sex toys, present a plausible means for transmission of infected cervicovaginal secretions.

In several studies, women who report sex with both men and women report more sex partners over their lifetimes than women who have sex exclusively with either men or women. One population-based survey in low-income neighborhoods found that women who had sex with men only reported a mean of 16 lifetime partners, whereas women reporting sex with men and women reported a mean of 307 lifetime partners. Similarly, among patients attending an STD clinic in Seattle, women with only female partners in the previous 2 months reported 3.4 partners in the past year; women with only male partners, 5.3 partners in the past year; and women with male and female partners, 16.5 partners in the past year. Women who report sex with both men and women are likely to be at higher risk for STDs than women who report sex with women or men only.

WSW may have male partners who are at higher risk for HIV and STDs than the partners of women who have sex with men only. In one study of patients at an STD clinic, 10% of women who had sex with only women in the previous 2 months had a prior male partner who was gay or bisexual, compared with 6% of women reporting sex with men only. Of women reporting sex with both men and women in the prior 2 months, 29% had a prior gay or bisexual male partner. Women who reported sex with both men and women in the previous 2 months were also more likely than women who had sex with only men or only women to have had more than four male sexual partners in a year, more likely to exchange sex for money or drugs, and more likely to have used intravenous drugs. In summary, lesbian and bisexual women may have past or current sex partners at high risk for HIV and other STDs.

Risk Reduction Counseling

No studies have directly addressed the acceptability or efficacy of STD risk reduction interventions among WSW. However, measures that reduce the potential for transmission of cervicovaginal secretions are likely to be effective in reducing STD transmission.

For women who practice digital-vaginal or digital-anal sex (hands or fingers in partner’s vagina or anus), the risk is probably low unless secretions are actually transferred on the hands from the infected partner to the other. Interrupting this progression by avoiding the behavior or by using and removing gloves after contact is likely effective.

For minimizing transfer of infected secretions associated with insertive sex toys, several approaches are likely effective. These include minimizing sharing of unclean sex toys (either not sharing toys at all or cleaning them between use by one partner and the other), use of condoms on sex toys, and avoiding use of sex toys anally and vaginally in succession.

With regard to oral sex and STDs, WSW may be at increased risk of genital herpes infection with herpes simplex virus type 1 (HSV-1) due to a relatively higher frequency of orogenital sex. Serologic screening for HSV-1 is not useful to screen for potential infectiousness, because most adults are infected with HSV-1 orally, and serology does not distinguish between oral and genital infection. However, women should be counseled to avoid performing oral sex when lesions consistent with an oral herpes outbreak (eg, a cold sore, recurrent ulcer, or vesicle) are evident or if a recognizable prodrome (eg, ear pain or local lymphadenopathy) is underway.

Other important components of complete risk reduction counseling for all patients include a discussion of sex partner selection, sexual network assessment, and the patient’s ability to negotiate safer sex practices. More detailed information can be found in Chapter 27.

Laboratory Studies

Screening of Asymptomatic Patients

Laboratory evaluation for STDs in WSW should closely mirror that for heterosexual women. With regard to STD screening of asymptomatic women without clinical findings, WSW should be screened for Chlamydia trachomatis as recommended by current screening guidelines (annually up to age 25 years or older, depending on risk). Although no data are available to estimate the risk of chlamydia transmission between women, chlamydial infection and pelvic inflammatory disease have been reported by WSW surveyed; further, WSW may engage in sexual networks that involve men, as previously noted, and may not be aware of their female partners’ exposure to men. No cases of gonorrhea transmission between women have been documented; given the relatively low prevalence of this STD in many clinical settings, routine screening for gonorrhea in asymptomatic WSW without relevant clinical symptoms is not indicated.

Other STDs in WSW deserve comment, but should not be sought in asymptomatic women who report no contact with a male or female partner with an STD. Each should be considered in the relevant clinical setting (eg, complaint of abnormal vaginal discharge or of genital ulcers).

Patients with Abnormal Vaginal Discharge

Bacterial Vaginosis

Bacterial vaginosis is highly prevalent among WSW and has been the most common diagnosis in WSW evaluated at STD clinics (frequently, it is more common in WSW than in heterosexual women at those clinics). Risks for bacterial vaginosis among WSW include a higher number of lifetime female sex partners, having a female sex partner with bacterial vaginosis, use of a shared vaginally inserted sex toy, and receptive oral-anal sex. The exact cause of bacterial vaginosis is unknown, but these data suggest that some factor that promotes or causes this enigmatic condition may be transmissible between women during sex. Whether female partners of women diagnosed with bacterial vaginosis should be routinely tested and treated is not known. One reasonable approach is to test a woman’s partner for bacterial vaginosis if she is symptomatic, or if the infection in the index case is recurrent, because treatment of the partner might theoretically effect a higher cure rate in the index case. However, the latter approach has not been studied.

Trichomoniasis

Other etiologies of abnormal vaginal discharge include infection with Trichomonas vaginalis, which has been self-reported in surveys by women with no history of prior sex with men and has also been reported as metronidazole-resistant trichomoniasis in both members of a monogamous lesbian couple. These data, along with the plausibility of transmitting vaginal fluid through the sexual practices of WSW, strongly support the conclusion that this infection can be transmitted in this manner.

Patients with Genital Lesions or Ulcers

Human Papillomavirus Infection

HPV, a group of viruses that causes anogenital warts and cervical cancer, may be transmissible between women by skin-to-skin contact, digital-genital contact, and use of shared sex toys. Women who report never having sexual contact with men have been found to have vulvar warts, cervical neoplasia associated with HPV, and high-risk (associated with oncogenic risk) HPV DNA by genetic testing (polymerase chain reaction). In one study, HPV DNA was detected by genetic probe in 19% of women who had no prior sexual contact with men, and 14% had cervical dysplasia. Anogenital warts and abnormal Pap smears were also self-reported by women with no prior sexual contact with men.

Importantly, the finding that HPV is present in women whose sexual contact with men is either remote or nonexistent has important implications regarding Pap screening for these women. Such women may consider themselves at low risk for cervical cancer, and their health care providers may assume the same. Thus, routine screening for cervical dysplasia may be neglected in these women. WSW should receive Pap screening for cervical dysplasia according to the same guidelines as other sexually active women.

HIV Infection

Case reports of sexual HIV transmission between women have been published, with a recent report substantiated by a finding of identical genotype of the HIV isolates from both women and a plausible clinical history. Oral-genital contact, mucosa-to-mucosa genital contact, sharing of blood or menstrual fluid, and contact with genital herpes lesions could facilitate transmission. Because the Centers for Disease Control and Prevention now recommends universal HIV screening in all primary care settings, WSW should be tested for HIV at least once, and retested depending on sexual risk behavior. Decisions to rescreen for HIV should be based on risk factors such as unprotected sex with men, particularly gay or bisexual men, number of recent female sex partners, and intravenous drug use.

Genital Herpes Infection

Genital herpes, usually caused by herpes simplex virus type 2 (HSV-2) but occasionally by HSV-1, can be transmitted by contact of mucous membrane to mucous membrane or vulnerable skin. Therefore, transmission between women is theoretically possible. Genital herpes has been reported in women who had no prior sexual contact with men. In a study of nearly 400 WSW in Seattle in 1998–2001, 2.6% of women who reported no male partners had antibodies to HSV-2. Likelihood of having HSV-2 antibodies increased with increasing lifetime number of male sex partners. The authors concluded that HSV-2 can be transmitted between women, although less efficiently than between men and women. Thus, routine screening for HSV-2 infection using type-specific serology is not recommended for WSW unless individual risk assessment indicates it should be performed (eg, history of unexplained genital lesions; recent multiple sex partners, especially men). In the Seattle study, the likelihood of WSW having antibodies to HSV-1, which typically causes oral herpes, increased with increasing number of lifetime female partners, suggesting a role for orogenital sex in facilitating transmission in this population. However, serologic screening is not indicated for this virus, because infection is widely prevalent, the test does not distinguish between oral and genital infection, and HSV-1 genital infection is associated with fewer recurrences and less subclinical shedding.

Syphilis

Although Treponema pallidum, the causative agent of syphilis, is relatively uncommon compared with the viral STDs discussed in the preceding paragraphs, sexual transmission between female partners has recently been reported. Because some WSW who choose to have sex with men may be more likely to choose bisexual men for partners, health care providers should bear in mind that recently the incidences of early syphilis and of fluoroquinolone-resistant Neisseria gonorrhoeae have markedly increased among men who have sex with men. Providers should thus screen and treat WSW appropriately based on STD risk assessment.

Available data strongly suggest that HPV, and probably other STDs (especially herpes simplex virus), are sexually transmitted between women. Thus, recommendations for Pap smear screening among lesbians should not differ from those for heterosexual women. Bacterial vaginosis may eventually be defined as an STD that is transmissible between women, but the exact etiology of the condition remains unknown. The recent increases in STDs among men who have sex with men but who do not identify as gay also emphasize that simply asking female patients their self-defined sexual orientation is not adequate. Assessment of specific sexual risk behaviors, and of previous sexual history, can provide a more complete tool for guiding the patient evaluation and counseling the patient about how to maintain sexual health.

• • The finding that HPV is present in women whose sexual contact with men is either remote or nonexistent has important implications regarding Pap screening for WSW. WSW should receive Pap screening for cervical dysplasia according to the same guidelines as other sexually active women.