Syphilis is a serious bacterial infection that can cause significant complications if undiagnosed and untreated.1 Syphilis is usually sexually transmitted but can also be transmitted to the foetus or neonate if a pregnant woman is infected, resulting in serious perinatal morbidity and mortality.2 Syphilis was once a common disease in the US and Europe in the 19th century when 8% to 14% of the population had serological evidence of having been infected. The widespread availability of penicillin after the Second World War led to a dramatic reduction in incidence.3 In New Zealand, the numbers of cases of syphilis were low for the latter part of the 20th century. A national rate was put at 3.0 cases per 100,000 in 1977 and no change in incidence was reported from sexual health clinics between 1986 and 1993.4 However, the total number of syphilis cases diagnosed annually in New Zealand is not known, as until recently the acquired immune deficiency syndrome (AIDS) was the only notifiable sexually transmitted condition. The recent passing of the Health Protection Amendment Bill means that some sexually transmitted infections (STIs) such as syphilis will become notifiable.
STI surveillance data is provided voluntarily to the Institute of Environmental Science and Research Limited (ESR) by sexual health clinics (SHCs), family planning clinics (FPCs) and laboratories.5 Between 2000 to 2005, numbers notified annually to ESR varied but were low and remained below 50, ranging from 13 in 2000 to 47 cases in 2005. After 2005, numbers increased but fluctuated with a peak of 144 cases notified nationally in 2009.
Since 2013, ESR has been collecting enhanced sentinel site surveillance data on cases of infectious syphilis diagnosed in SHCs following a multi-centre pilot study that received ethics approval. Enhanced surveillance requires additional information on each case such as sexual behaviour and co-infections with other STIs including HIV.
In 2013, 81 cases of infectious syphilis were reported to ESR from SHCs in New Zealand. The highest number of cases was in Auckland (41) followed by Canterbury (18 cases).6 The majority of cases in 2013 were diagnosed in gay and bisexual men (GBM). The numbers of reported cases continued to increase in 2014 with 141 cases notified to ESR; 85 of these were in Auckland.7 In 2015, an increase in cases of infectious syphilis treated by the Auckland Regional Sexual Health Service (ARSHS) was noted. The aim of this audit is to briefly report on the large increase in syphilis cases to draw attention to this alarming trend and to add some regional context to the annual ESR STI surveillance report.
The ARSHS sends a monthly report to the Institute of Environmental Science and Research Ltd (ESR) of numbers of sexually transmitted infection diagnoses including infectious syphilis. In addition, ESR requires an enhanced surveillance form to be completed for each case of infectious syphilis that is notified. The clinician managing the case is responsible for completing the form which includes demographic, behavioural, laboratory and clinical information specific to that case. The data on the surveillance form is anonymised but contains unique identifying codes in order to prevent duplication of data. ESR collates all the enhanced syphilis surveillance data from around the country for the annual STI surveillance report, which is usually published in the second half of each year.
Diagnosis of syphilis
Syphilis is due to infection with the spirochaete Treponema pallidum, which cannot be grown on conventional bacterial culture media. Therefore it is usually diagnosed serologically. If syphilis serology is requested the laboratory performs a screening treponemal EIA assay and if this is reactive, further supplementary testing is done in the form of a treponema pallidum particle agglutination assay (TPPA) and a rapid plasma reagin test (RPR, which is a non-specific serological test). Supplementary testing is important for confirmation and for staging purposes; however, distinction between infectious, non-infectious or treated syphilis also requires a full history and clinical assessment to properly interpret significance of results. The natural course of untreated disseminated syphilis is to resolve spontaneously and the person becomes non-infectious to sexual contacts after one to two years.5
ARSHS has maintained an excel database of all infectious syphilis cases diagnosed each year since 2013. The syphilis database is kept up to date by conducting a regular search of the ARSHS electronic patient management system (HCC) for new diagnoses of syphilis. The patient records for each case are then checked to ensure that the clinical history, assessment and laboratory results are consistent with the ESR case definitions for infectious syphilis7 and any incorrectly classified cases are re-coded as non-infectious, and ESR is notified so that they can amend their records. Additional data was added to the database for each case for the purposes of this study, including sexual behaviour, presenting symptoms, rapid plasma reagin (RPR) titre, source of referral, HIV serostatus and other STI diagnoses. Demographic, clinical and behavioural variables of those cases fitting the definition of infectious syphilis were then summarised.
ESR case definitions
There are four different categories of infectious syphilis that can be reported to ESR: primary, secondary, early latent and unknown duration. Confirmed cases must either have reactive serological tests for syphilis or have Treponema pallidum organisms detected from clinical lesions, as serology may sometimes be negative in cases of early syphilis. Cases are categorised according to presence or absence of symptoms into primary or secondary syphilis (symptomatic); or early latent syphilis or syphilis of unknown duration (asymptomatic). Primary and secondary syphilis cases must have presented with compatible clinical symptoms and signs such as genital ulceration or rash confirmed by examination. To be classified as early latent, cases must have had no clinical symptoms or signs of syphilis plus one of the following: a clear history of primary or secondary syphilis symptoms within the previous two years, a history of sexual contact with a confirmed case of infectious syphilis within the previous two years, a documented four-fold or greater rise in RPR titre (if history of previous treated syphilis) or documented seroconversion to reactive treponemal serology within the previous two years. Some cases are difficult to classify as there may be incomplete clinical information or previous syphilis serology, however, it is known there is a clear relationship between RPR titre, infectiousness and duration of infection.8 To be classified as infectious of unknown duration, the case must have had no clinical signs or symptoms of syphilis, no previously documented reactive treponemal serology and a rapid plasma reagin (RPR) titre greater than 1:16.
The study was approved by the Northern A health and disability ethics committee: reference number 16/NTA/26.
There were a total of 152 cases of infectious syphilis managed at ARSHS in 2015, which was a 78% increase from the previous year (84 cases). Three of these cases were re-infected within the same year, so there were 149 affected individuals. The crude incidence rate for cases of syphilis managed by ARSHS was 9.5 cases per 100,000 for the year 2015, based on Statistics New Zealand’s Auckland region population estimate of 1,570,000 (June 2015). Figure 1 shows the dramatic increase in quarterly numbers of cases diagnosed at ARSHS from 2013 to 2015. Seventy-one cases (47%) presented in the last quarter of 2015 alone.
Figure 1: Auckland quarterly syphilis diagnoses 2013–2015.
GBM = gay and bisexual men; HS=heterosexual.
The summary of data is presented in Table 1—note that the denominator changes depending on whether it is referring to demographics (149) or clinical characteristics of each case (152). As in previous years, the majority of cases were male (92%) and most of these were GBM. Seventeen men (11%) disclosed both male and female sexual contacts. Although the number of heterosexuals (HS) diagnosed in 2015 was small (35), numbers had almost quadrupled from the nine cases diagnosed at ARSHS in 2014 (data not shown).
Table 1: Summary of 2015 data.
HIV serostatus (GBM)
Chlamydia and gonorrhoea
Sixty percent of cases were diagnosed in people of European ethnicity. Most people presented to the service without a referral (53%), 30% were referred by their general practitioner (GP) and 1% were referred by the Infectious Diseases service. The majority of cases presented with symptoms (61%) of primary or secondary syphilis. Of the primary syphilis cases; 36 presented with penile ulcers, one presented with an oral lesion and five cases presented with anal ulcers. One patient was admitted to hospital with neurosyphilis. Just over one third of cases were also infected with HIV (all GBM), which was a similar proportion to previous years.4 Twenty-two percent of cases were diagnosed with another sexually transmitted infection (STI)—the most common being chlamydia—and 13 cases were diagnosed with more than one other STI.
It would appear from these results that there has been a significant increase in infectious syphilis cases treated by the ARSHS. The 152 cases treated in 2015 is the largest number to date and is a worrying trend, particularly because the total number of cases in Auckland is likely to be higher due to under-reporting. A previous study using laboratory data in Auckland found that 28% of identified cases were managed outside the regional sexual health service and so were not reported to ESR (unpublished data).9 That study found a crude incidence rate of 7.0 cases per 100,000 in 2007. These latest figures indicate this has increased to 9.5 cases per 100,000 in 2015. This compares to a national incidence rate of 3.1 cases per 100,000 diagnosed in sexual health clinics in 2014.10
Other developed countries have shown similar trends in notifications of infectious syphilis. In Australia 1,765 cases were notified in 2013, which was the highest number reported in recent surveillance. The rate of diagnoses for syphilis in males rose from 5.0 per 100,000 in 2004 to 14.0 per 100,000 in 2013 and was predominantly diagnosed in GBM.11 In the US the national rate of reported primary and secondary syphilis cases was low at 2.1 cases per 100,000 in 2000. Since then the number of cases has increased every year with a national rate of 6.3 cases per 100,000 in 2014, mainly attributable to increased cases among GBM.12 This trend has also been noted in the UK; there was a 33% increase in notified syphilis cases from 2013 to 2014, mainly in GBM.13 Alongside the increased syphilis incidence rates in developed countries there has also been increasing notifications for HIV in GBM. In New Zealand HIV prevalence rates in GBM are lower than most developed countries, and behavioural surveys between 2002 and 2014 show that high condom use is being sustained. However, multiple factors influence condom use in GBM as they are not a homogenous group. Those recruited for behavioural surveys online report less condom use, more complex sexual partnering patterns, are younger and more bisexually identified than those recruited offline. GBM recruited in sex on site venues report much higher rates of partner change than GBM recruited in other venues.14 Syphilis can enhance both the transmission and acquisition of HIV,15 so early diagnosis and treatment of identified cases may reduce an individual’s risk of acquiring HIV. A study by Katz et al found that GBM were at higher risk of HIV after being diagnosed with another STI. Those diagnosed with early syphilis had an incident rate of 2.8 per 100 person years compared with an overall incidence rate of 0.4 per 100 person years.16 It is likely that behaviour change in some GBM is driving current increases in both syphilis and HIV incidence in New Zealand. The fact that 22% of ARSHS cases were diagnosed with another STI highlights the importance of comprehensive STI screening when testing for syphilis.
While GBM is the main group affected by syphilis, there is considerable concern in both the UK and US about increases in the numbers of congenital cases. In the US the syphilis rate in women fluctuated between 0.8 and 0.17 cases per 100,000 in the early part of the century until the period from 2013 to 2014 when there was a 22.7% increase in the syphilis rate in women.12 In the UK between 2000 and 2007, diagnoses of syphilis in women increased by 474% (from 78 to 448). The increase in syphilis in women has been mirrored in both countries by corresponding increases in cases of congenital syphilis. In the US reported congenital syphilis rates increased from 9.1 cases per 100,000 in 2013 to 11.6 cases per 100,000 in 2014.12 In the UK there has been a re-emergence of congenital syphilis, with about six cases per year reported in GUM clinics.17 There is a real concern this could happen in New Zealand, with the recent increased number of cases in heterosexuals, although only one congenital case has been reported in the literature in recent years.18 Syphilis serology is routinely performed as part of the first antenatal screen, however, this will not rule out syphilis acquired later in pregnancy and serological tests may be falsely negative if performed during incubating syphilis.The authors of the case report caution that “it is important to check maternal serology and consider this disease in any child with suspicious clinical findings, particularly if antenatal screening has not occurred, but even if the initial pregnancy screening on the mother has been negative”.
The principles of syphilis control have not really changed since the last century when better diagnostic tests and effective treatment became available.19 These include: regular screening of affected populations for timely diagnosis, correct treatment, follow-up over 12 months to ensure serological cure and rigorous partner notification. To enable this, health professionals need to be aware of who to screen (as a large proportion of cases are asymptomatic), signs and symptoms of syphilis, how to manage and when to refer. As management of syphilis and interpretation of serology requires significant expertise including eliciting a full sexual health history; referral or discussion of cases with a specialist is strongly recommended if the practitioner has limited experience with syphilis.
In June 2015 an alert was sent to primary care practitioners and emergency departments from ARSHS and the Auckland regional public health service (ARPHS) with advice to: serologically screen all people at risk of STI for syphilis, to screen men who have sex with men at least annually and to refer or discuss any suspected cases with the regional sexual health service, as per New Zealand Sexual Health Society guidelines.20 Also to test anyone presenting with a generalised body rash or with a rash affecting the palms of the hands or soles of the feet, pyrexia of unknown origin, unexplained persistent lymphadenopathy, unexplained liver function disturbance, patchy alopecia, unexplained neurological symptoms including meningitis, stroke syndromes and cranial nerve palsies. Advice to lead maternity carers (LMCs) was that maternal serological status be documented and that women who had had a change of sexual partner during pregnancy should be re-tested. It is probable that this public health alert was responsible for some of the increase in cases seen at ARSHS in the second half of 2015, as well as health promotion activities being carried out by the New Zealand AIDS Foundation around the same time period.21
So in conclusion, numbers of syphilis cases managed by the Auckland regional sexual health service are at their highest in recent decades. The increased numbers could be a precursor to a rise in congenital syphilis cases if this outbreak is not contained. As syphilis is often asymptomatic, it is important that all persons at risk of STI are tested and that sexually active GBM in particular are tested regularly, even if using condoms, as syphilis is easily transmitted through oral sex.22 Health professionals need to be made aware of who to test and how to refer any suspected cases to a specialist service, as management and interpretation of syphilis serology requires some expertise. Better surveillance and management will be possible once syphilis is made a notifiable condition.