Increase in congenital syphilis cases and challenges in prevention in Japan, 2016–2017

Keywords: Asia, Japan, social determinants, surveillance, syphilis, women, partner testing, pregnancy, syphilis screening.

Concomitant with the rise in syphilis in Japan,^1,2 congenital syphilis (CS) notifications have increased, from four cases (0.4 case per 100 000 live births) in 2012 to 14 cases (1.4 case per 100 000 live births) in 2016.³ In response, we conducted a case series to identify key characteristics of CS patients and their mothers, along with challenges.³ Eligible subjects were CS patients who were notified through national surveillance from March 2016 to October 2017 and their mothers. Information was collected using a questionnaire and face-to-face interviews with the patients’ mothers and physicians (see³ for methods).

Of the 17 CS patients notified, 13 of their mothers consented to participate. Nine were symptomatic, with a wide clinical spectrum at diagnosis (Table 1). The four asymptomatic CS patients were tested because their mothers had syphilis but had no or insufficient treatment during pregnancy. Most CS patients were tested by fluorescent treponemal antibody absorption (FTA-ABS) immunoglobulin M (IgM) antibody assay (Table 1), and 11/13 were treated with intravenous benzylpenicillin injection.

Table 1.  Key sociodemographic and clinical characteristics of patients with CS and their mothers (n = 13)
RPR, rapid plasma reagin; PCR, polymerase chain reaction

Common characteristics among the mothers were young age, unmarried, having a lower educational attainment, having other sexually transmissible infections (STIs), a history of commercial sex work, and no or inadequate prenatal care visits (Table 1). Three mothers who did not make any prenatal care visits were diagnosed with syphilis by a screening test at delivery. Three other mothers made visits irregularly, which prevented timely diagnosis. More than half (7/13), however, were making regular prenatal care visits. Four of these seven mothers tested negative at their first trimester test and were diagnosed after their infants’ diagnosis of symptomatic CS; three experienced signs/symptoms of early syphilis (acute pharyngitis, severe itching and/or eczema) during pregnancy and consulted their respective physicians at the time but went undiagnosed. The other three were those with a past syphilis diagnosis; though two tested positive for syphilis during the first trimester, CS was not prevented due to misdiagnosis as inactive syphilis or discontinuation of medication because of hyperemesis. Another was also initially diagnosed as past infection, but retesting during the third trimester indicated current, active infection. Regarding testing of sexual partner(s), only three mothers’ partners were reportedly tested, with all three diagnosed with syphilis and two reportedly treated for syphilis.

In conclusion, while many mothers of CS patients had inadequate prenatal care visits as reported previously,^4–9 more than half of them had made routine visits, receiving a syphilis test at their first trimester. The four mothers who tested negative may have been infected during pregnancy; such events could have increased given the increased syphilis prevalence among heterosexuals.^1,10,11 Similar findings were recently reported from England and the US.^12,13 In addition, a mother was misdiagnosed with inactive syphilis; such ‘false negative’ diagnosis would also be expected to increase with higher syphilis prevalence (i.e. decrease in the negative predictive value of diagnosis).

During times of high syphilis prevalence, we emphasise the need for careful and sensitive diagnosis of syphilis in pregnant women. Clinicians should consider additional syphilis testing at the third trimester of pregnancy for high-risk women.^4,12,14 There is also a need to raise awareness for STI prevention among pregnant women, including partner testing. Inadequate communication regarding partner testing may have hindered timely diagnosis,^3,15 and healthcare providers could help facilitate communication. While challenges exist, our findings led to a multi-pronged response from the national and local governments, together with the medical sector – updating of the national clinical guidance for syphilis, additional reporting requirements for surveillance, and development of locally-appropriate educational pamphlets. It is our hope that these approaches will contribute to CS prevention, both for the ongoing outbreak and any future re-emergence of syphilis.

The authors declare that they have no conflicts of interest.

This study was supported by a grant from the Ministry of Health, Labour and Welfare of Japan (H27-Shinkou-Ippan-001).