Maternity Care Calendar and Guidelines: Screening for herpes simplex

Background

The 2 herpes simplex virus types; type 1 (HSV-1) and type 2 (HSV-2) share enough antigenic determinants that antibodies to one are capable of neutralizing the other.[1] Initial contact with HSV generally occurs in childhood, is often asymptomatic and usually involves HSV type 1.[1] HSV-1 is responsible for most herpes labialis, gingivostomatitis and keratoconjunctivitis. Approximately 90% of adults have antibody to HSV-1.[2] Although most genital infection is from HSV-2, either type can result in genital herpes infection. Approximately 30% of women in the US have antibodies to HSV-2.[1] The first population estimates of HSV-2 seroprevalence in Canada were determined through an anonymous unlinked seroprevalence study of stored sera of pregnant women in British Columbia in 1999. [3] The overall age-adjusted prevalence for HSV-2 was 17.3%, ranging from 7.1% in women 15-19 years to 28.1% in women age 40-44.

There are 3 stages of HSV clinical infection, determined by clinical presentation and serology:[1]

Primary genital HSV - no antibodies to HSV-1 or HSV-2 are present when patient is infected with HSV-1 or HSV-2. Nonprimary first-episode genital HSV -acquisition of genital HSV-1 or HSV-2 with preexisting antibodies to the other type. Recurrent genital herpes - reactivation of genital HSV when there are preexisting antibodies to the type involved.

In practice it can be difficult to differentiate between primary disease and a non-primary first episode without serologic testing.

HSV is transmitted through direct contact. One study showed that that annual rate of transmission of HSV between partners who were discordant for HSV infection was 31.9% for women with no antibodies to HSV-1 or HSV-2 and 9.1% for women with HSV-1 antibodies. [1] More than 50% of the cases of transmission were the result of asymptomatic shedding, making this virus particularly difficult to control and prevent.

Rates of vertical transmission at the time of delivery are 50% for primary HSV, 33% for non-primary first episode and 0-3% for recurrent HSV. [1] [2]Genital herpes that is acquired during pregnancy is not generally thought to be associated with an increase in neonatal illness or congenital HSV infection as long as HSV seroconversion has completed by the time of labour. [2, 4]There have been case reports of hematogenous spread of HSV to the fetus in early pregnancy resulting in fetal anomalies similar to the other TORCH infections.

Neonatal HSV, acquired in the birth canal can cause localized disease in the skin, eye or mouth (no associated mortality), CNS disease (15% mortality) or disseminated disease (57% mortality).[1]

Serologic Testing:
Traditional HSV antigen enzyme immunoassays (EIAs) do not distinguish between HSV-1 and HSV-2.[2] In recent years, type-specific serologic tests have become available. Assays such as the western blot are 98% sensitive and 100% specific for detecting HSV -2. [4] However, the western blot is not widely available.[2, 5, 6] Gull Laboratories in the US is marketing a HSV type-specific serology kit that is less expensive and labour intensive. [4]

A number of authors have proposed that HSV type-specific serologic testing should be carried out routinely in pregnancy.[7, 8] Women who were found to be HSV-2 seropositive could be counseled to recognize the symptoms of their reactivations and about the option of aciclovir (acyclovir) at term to decrease the risk of Caesarian section. Also, invasive procedures such as the use of fetal scalp clips, artificial rupture of membranes, forceps and vacuum extractors should be avoided if possible. [9]The partners of seronegative women, could also be tested and discordant couples could be counseled about the risk of neonatal HSV if herpes is acquired at term as well as how to decrease this risk (abstinence/condoms/suppression of the seropositive partner with acyclovir during the pregnancy). HSV negative women with HSV-1 seropositive partners should be counselled to avoid oral genital contact in the second half of pregnancy. [9] As one author advocating routine type-specific serology for all pregnant women explains, caesarian section of all women with recurrent genital herpes is not an efficient strategy for preventing neonatal HSV, because most symptomatic lesions are caused by recurrent HSV-2, while most neonatal herpes is caused by asymptomatic first episodes. [4, 9] Because of the relatively low risk of vertical transmission, he states that HSV-2 seropositive women with genital lesions in labour could be considered for vaginal delivery. Women with recurrent genital HSV-1, those who are seroconverting to HSV-1 or HSV-2 or those whose serostatus is unclear should undergo caesarian section. The Canadian STD Guidelines state that type-specific serology should be considered to identify when pregnant women with no history of herpes are at risk of primary herpes infection from a partner.[10]

However, others have argued against type-specific serologic screening, particularly in the UK where the prevalence is lower than the US.[6, 11-13] One British study found that the intervention would not be cost-effective, costing between £100, 000 to £4 million per case of severe neonatal herpes prevented. [11] An American cost-effectiveness analysis similarly found that it would cost hundred of thousands - 4 million dollars per case of neonatal HSV prevented.[14] Also, concerns have been raised about the potential emotional impact of the test results on couples and the lack of evidence demonstrating that counselling interventions are effective in preventing the spread of STDs.[14] One author points out that most neonatal HSV would not be prevented by screening.[14]

Most authors advocate questioning all pregnant women and their partners about a history of herpes. [5, 15-19]. Women whose partners have genital herpes should be counselled regarding how to avoid sexual transmission. Individuals with orolabial herpes should be counselled about avoid transmission through oral genital contact and avoiding transmission to the newborn through kissing.

• Fair evidence exists to exclude weekly screening for herpes simplex virus from the routine prenatal care of high risk women. [D, II-2]. (High risk is defined as women with positive test results, history of recurrent herpes simplex, active disease during current pregnancy, and those with sexual partners who have genital herpes simplex.)
• Poor evidence exists to include or exclude cesarean section for delivery of pregnant women with positive findings of herpes simplex virus at clinical examination [C, III]

• Routine screening for genital herpes infection in asymptomatic pregnant women by surveillance cultures or serology is not recommended (D Recommendation)
• Practitioners should consider asking all pregnant women whether they or their sexual partner(s) have had genital herpes
• They found insufficient evidence to recommend for or against routine counseling of all pregnant women who have no history of genital herpes, but whose partners do have a positive history to use condoms or abstain from intercourse during pregnancy (C Recommendation) Counseling can be recommended however, on other grounds including lack of risks and potential benefit from the intervention.

• All pregnant women should be asked about a history of genital herpes
• At the onset of labour, all women should be questioned about symptoms of herpes and examined for signs of infection
• Women without a history of genital HSV should be counseled to avoid intercourse in the third trimester with partners known or suspected of having genital HSV.
• Pregnant women without a history of orolabial herpes should be advised to avoid cunnilingus during the third trimester with partners known or suspected to have orolabial herpes.
• In the absence of lesions during the third trimester, routine serial cultures for HSV are not indicated for women with a history of recurrent HSV. Prophylactic Caesarian section is not indicated for women who do not have active genital lesions at the time of delivery

• They note that "some specialist believe that type-specific serologic tests are useful to identify pregnant women at risk for HSV infection and to guide counselling with regard to the risk of acquiring HSV during pregnancy." This may be especially important when the woman's sexual partner has HSV infection.

• "virologic monitoring is not recommended for pregnant women whose onset of disease antedated pregnancy or for those whose sexual partners have had herpetic lesions" and
• "there is no data to support the value of culturing asymptomatic patients with a history of recurrent disease"
• mothers, family members and hospital staff with active HSV lesion (oropharygeal, cutaneous) should be aware that postnatally acquired neonatal HSV can be devastating. Mothers with active HSV should handle their infants with caution and others should avoid direct contact.

• All women should be questioned about a history of genital HSV infection. "couples should be educated about the natural history of genital HSV infection and should be advised that, if either partner is infected, they should abstain from contact while lesions are present." They also recommend use of condoms for asymptomatic HSV infected individuals. Susceptible pregnant women should avoid sexual contact during the last 6-8 weeks of pregnancy if their partners have active genital HSV.
• Mothers with HSV should be instructed about how to avoid transmission of the virus to the infant. Measures such as meticulous hand washing, covering herpetic skin lesions and avoiding kissing when orolabial lesions are present should be reviewed. Women with active HSV can breastfeed as long as there are no vesicular lesions on the breast area.

• All pregnant women should be questioned during prenatal visits about any personal history of genital HSV infection or similar history in their sexual partner(s). Signs and symptoms of current genital HSV infection should be checked in all patients during the pregnancy.
• Weekly antepartum cultures are not recommended, even in women with a history of genital HSV infection

• "All women should be asked at their first antenatal visit if they or their male partner have ever had genital herpes. Female partners of men with genital herpes, who themselves give no history of genital herpes, should be advised about reducing their risk of acquiring infection." (by avoiding intercourse when their partner has an HSV recurrence) They note that the impact of this intervention is limited by the common occurrence of asymptomatic shedding. Condom use throughout pregnancy should be considered. (level IV evidence -expert opinion/committee report)
• "identifying women susceptible to acquiring genital herpes in pregnancy by means of type specific antibody testing has been evaluated in the UK in terms of costs and benefits and is not indicated except in the context of further research" The report acknowledges that history is not an accurate way of determining a woman risk of acquiring primary HSV, because of the prevalence of unrecognized infection. They felt that identifying serologically discordant couples and counseling about reducing the risk of HSV exposure (abstinence and/or condom use) would not likely be cost effective.

• All women should be asked at their first antenatal visit if they or their partners have ever had genital herpes
• Asymptomatic female partners of men with herpes should be advised not to have sex during recurrences. Condoms may be recommended.
• Pregnant women should be advised of the risk of acquiring HSV-1 as a result of orogenital contact
• Identifying susceptible women by means of type specific serology has not been shown to be cost-effective

• Ask about a history of herpes in women & partner (genital, orolabial)
• Women with no history of HSV should be counseled about avoiding exposure near term (if partner is HSV-positive: advise abstinence, condom use, and/or antiviral suppression of partner, avoidance of oral genital contact if partner has orolabial herpes)
• Women with recurrent HSV should be counselled about the option of acyclovir at term, the role of caesarian section and avoiding transmission to the infant postpartum.



• Type-specific HSV serology may be appropriate in some cases where available
• in plain font as most evidence for screening is grade C or expert opinion
• It would be located under "Clinical" suggested for preconception visit (or alternatively, early pregnancy)