Syphilis (case definition only)

Part of the Communicable Disease Control Manual

Chapter last reviewed and updated in June 2022. A description of changes can be found at Updates to the Communicable Disease Control Manual.

Contents

Case definition – infectious syphilis

(See the next section for congenital syphilis.)

Infectious syphilis is notifiable in New Zealand. This includes syphilis of less than 2 years’ duration (primary, secondary and early latent) and syphilis of unknown duration. Late latent syphilis and tertiary syphilis are not notifiable in New Zealand.

Clinical description

For notification purposes, any of the following findings provide clinical evidence for infectious syphilis:

Primary syphilis

  • A primary chancre (or ulcer) is present. It is usually a painless, solitary oral, genital or anal ulcer. 

Note: Some ulcers may be painful or multiple. Chancre occurs at site of contact with another person’s infectious lesions and may appear as a papule before ulcerating.

Secondary syphilis

  • Signs of secondary syphilis include: oral or genital mucocutaneous ulceration; rash affecting the body, palms or soles; condylomata lata (large, raised, whitish or grey, flat-topped warty lesions found in warm, moist areas); patchy alopecia; and lymphadenopathy.

Note: The rash of secondary syphilis often resembles a drug reaction, pytariasis rosea or guttate psoriasis.

Early latent syphilis

Syphilis is of less than 2 years’ duration in a person who has no symptoms or signs of infection at the time of diagnosis. This includes currently asymptomatic people who have a history of symptoms consistent with primary or secondary syphilis within the last 2 years.

Laboratory test for diagnosis

Laboratory definitive evidence requires at least one of the following:

  • seroconversion in the past 2 years: a reactive treponemal-specific test (EIA, TPPA, TPHA or FTA-Abs)[1]  when a previous treponemal-specific test was non-reactive within the past 2 years and the latest result is confirmed by either a reactive non-treponemal test (RPR or VDRL)[2] or a different reactive treponemal-specific test
  • documented fourfold or greater rise in non-treponemal antibody titre (RPR or VDRL) compared with the previous titre within the past 2 years and there is a reactive treponemal-specific test (EIA, TPPA, TPHA or FTA-Abs).

Laboratory suggestive evidence requires at least one of the following:

  • detection of Treponema pallidum by direct fluorescent antibody microscopy (direct antigen test) or by nucleic acid testing (eg, polymerase chain reaction, PCR)
  • a reactive treponemal-specific test (EIA, TPPA, TPHA or FTA-Abs) and either a reactive non-treponemal test (RPR or VDRL) or confirmation by a different reactive treponemal-specific test.

Note:

  • IgM assays should not be used for screening purposes for infectious syphilis
  • T. pallidum-specific rapid immunochromatography (ICT) assays for use as point-of-care tests are becoming available, but their performance has not yet been fully established. Positive ICT results should be confirmed with a second treponemal-specific assay.

Case classification

  • Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
  • Probable: The case definition for a confirmed case is not met and either:
    • the person has no known previous reactive serology, and has no history of adequate treatment of syphilis or endemic treponemal disease,[3] and has laboratory suggestive evidence, and has at least one of the following:
      • history of sexual contact with an infectious case within the last 2 years
      • RPR ≥16
      • history of symptoms consistent with primary or secondary syphilis within the last 2 years (discussion with a sexual health or infectious diseases physician is recommended)
      • positive syphilis IgM
    • the person has previous reactive serology, and has a fourfold or greater rise in non-treponemal antibody titre (RPR or VDRL) when the previous serology was done more than 2 years ago, and has at least one of the following:
      • contact with an infectious case within the last 2 years
      • positive syphilis IgM.
  • Confirmed: A case that has laboratory definitive evidence alone, or laboratory suggestive evidence and clinical evidence.
  • Not a case: A case that has been investigated and subsequently found not to meet the case definition.

Note: Direct detection of T. pallidum in mucocutaneous lesions is evidence of a confirmed case even if the serology is negative as seroconversion may not occur for up to 3 months after infection.

Case definition – congenital syphilis

(See the previous section for infectious syphilis.)

Clinical description

T. pallidum crosses the placenta and infects the fetus at any time in pregnancy. If untreated, this can result in intrauterine fetal death, stillbirth or a baby with congenital syphilis. In early congenital syphilis, the baby may be severely affected at birth (eg, hepatomegaly, ascites, hydrops, fetal anaemia) or, more frequently, may appear normal. If the diagnosis is not made at that time, the baby will present later – nearly always within 3 months of birth – with non-specific complaints (eg, rhinitis, failure to thrive, pneumonia).

Clinical evidence of congenital syphilis:

  • a live or stillborn child with any of the following evidence suggestive of congenital syphilis on physical examination: anaemia; osteochondritis; hepatosplenomegaly; skin rash; condylomata lata; rhinitis (snuffles); pseudoparalysis; meningitis; ascites; intrauterine growth retardation; or any other abnormality not better explained by an alternative diagnosis
  • any features suggestive of congenital syphilis on radiographs of long bones
  • an elevated CSF cell count or protein (without other cause)
  • the mother is seropositive in the perinatal period and has no documented evidence of adequate treatment
  • a pathologist or clinician with relevant skills in congenital infections makes a clinical diagnosis of congenital syphilis, including in the event of a stillbirth or neonatal death.

Laboratory test for diagnosis

Laboratory definitive evidence for a live birth requires:

Mother and child both seropositive by a treponemal specific test (EIA, TPPA, TPHA, TPLA or FTA-Abs), and the child is a live birth, and one or more of the following:

  • direct demonstration of Treponema pallidum by any of the following methods: nucleic acid amplification (NAA) test including polymerase chain reaction (PCR); dark field microscopy; fluorescent antibody, silver stain or immunohistochemical methods – in specimens from the child from: lesions; nasal discharge; cerebrospinal fluid (CSF); autopsy material; or other appropriate test sites; or from the placenta; umbilical cord; or amniotic fluid
  • detection of Treponema pallidum specific IgM in the child
  • the child’s serum non-treponemal (RPR or VDRL) serology titre at birth is at least fourfold greater than the mother's titre.

Laboratory suggestive evidence for a live birth requires:

Mother is seropositive by a treponemal specific test (EIA, TPPA, TPHA, TPLA or FTA-Abs) or the mother is seropositive by a Treponema pallidum-specific rapid immunochromatography, and the child is a live birth, and one or more of the following:

  • direct demonstration of Treponema pallidum as described under laboratory definitive evidence for a live birth but without serological confirmation in the child
  • child seropositive on non-treponemal testing (RPR, VDRL) in the absence of IgM testing
  • a reactive cerebrospinal fluid (CSF) non-treponemal test (ie, VDRL) in a non-traumatic lumbar puncture on the child
  • a child who remains seropositive by a treponemal-specific test (EIA, TPPA, TPHA, TPLA or FTA-Abs) at 15 months of age, which is confirmed either by another, different reactive treponemal specific test or a reactive non-treponemal test (RPR or VDRL), in the absence of post-natal exposure to Treponema pallidum, including the non-venereal subspecies Treponema pallidum subsp. pertenue (Yaws) or subsp. endemicum (Bejel, endemic syphilis) or Treponema carateum (pinta).

Laboratory definitive evidence for a stillbirth requires:

Mother is seropositive by a treponemal specific test (EIA, TPPA, TPHA, TPLA or FTA-Abs), and the pregnancy outcome is a stillbirth, and there is evidence of infection in-utero through:

  • direct demonstration of Treponema pallidum in the fetus by any of the following methods: nucleic acid amplification (NAA) test including polymerase chain reaction (PCR); dark field microscopy; fluorescent antibody, silver stain or immunohistochemical methods – in specimens from: lesions; nasal discharge; cerebrospinal fluid (CSF); autopsy material; or other appropriate test sites.

Laboratory suggestive evidence for a stillbirth requires:

Mother is seropositive by a treponemal specific test (EIA, TPPA, TPHA, TPLA or FTA-Abs) or the mother is seropositive by a Treponema pallidum-specific rapid immunochromatography, and the pregnancy outcome is a stillbirth, and there is:

  • direct demonstration of Treponema pallidum by any of the following methods: nucleic acid amplification (NAA) test including polymerase chain reaction (PCR); dark field microscopy; fluorescent antibody, silver stain or immunohistochemical methods – in specimens from: placenta; umbilical cord; amniotic fluid.

Case classification

  • Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
  • Probable: A case that has clinical evidence and laboratory suggestive evidence.
  • Confirmed:
    • Live birth: A case with laboratory definitive evidence.
    • Stillbirth: A case with laboratory definitive evidence in which a pathologist or clinician experienced in congenital syphilis makes a clinical diagnosis of congenital syphilis at autopsy.

Adequate treatment during pregnancy does not exclude the diagnosis of congenital syphilis if criteria for a confirmed or probable case are met.

Spread of infection

Reservoir

Humans.

Incubation period

Primary syphilis: usually 3 weeks; range 10 days to 3 months.

Note: Secondary syphilis may occur immediately after primary syphilis or up to 6 months later.

Mode of transmission

Transmission most commonly occurs by sexual contact (oral, vaginal or anal sex), and less commonly by non-sexual contact, with skin lesions and mucous membranes of an infected person.

Transmission can also occur transplacentally and through blood transfusions.

Infected infants may also have infectious mucocutaneous lesions.

Period of communicability

If untreated, the infectious period is defined as the first 2 years of infection. However, syphilis is most infectious during the primary and secondary stages of the disease when moist mucocutaneous lesions are present. 

Transplacental transmission may occur for at least 4 years after infection.

Transmission through blood transfusions can occur if the donor is in the early stages of disease.

For information on case management and contact tracing and management, please refer to the New Zealand Sexual Health Society syphilis management guidelines


[1] Treponemal-specific tests are IgG immunoassay (EIA), Treponema pallidum haemagglutination assay (TPHA), Treponema pallidum particle agglutination assay (TPPA), fluorescent treponemal antibody absorption (FTA-Abs) and IgM immunoassay (IgM-EIA).

[2] Non-treponemal tests are rapid plasma reagin (RPR) and venereal disease research laboratory (VDRL).

[3] Endemic treponemal diseases include yaws, bejel and pinta.

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