Syphilis (case definition only)

Part of the Communicable Disease Control Manual

Chapter last reviewed and updated in September 2018.

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 premature 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).

Any one of the following four findings meets the clinical criteria for notification of a probable case:

  • any evidence of congenital syphilis on physical examination (includes stillbirth[4])
  • any evidence of congenital syphilis on radiographs of long bones
  • an elevated cerebrospinal fluid (CSF) white cell count or protein (without other cause) in the child
  • the mother is seropositive in the perinatal period and has no documented evidence of adequate treatment in line with the New Zealand Sexual Health Society’s syphilis guidelines.

Laboratory test for diagnosis

Laboratory definitive evidence requires:

  • a treponemal-specific test (EIA, TPPA, TPHA or FTA-Abs)[1] confirming both mother and child are seropositive and
  • at least one of the following:
    • detection of T. pallidum by either nucleic acid testing (eg, PCR) or direct fluorescent antibody (DFA) in specimens from lesions, nasal discharge, CSF, placenta, umbilical cord, amniotic fluid or autopsy material
    • detection of T. pallidum-specific IgM in the child
    • the child’s serum non-treponemal (RPR or VDRL)[2] serology titre at birth is at least fourfold greater than the mother's titre.[5]

Laboratory suggestive evidence requires at least one of the following:

  • detection of T. pallidum by either nucleic acid testing (eg, PCR) or DFA but without serological confirmation in the child
  • the child is seropositive on non-treponemal testing (RPR or VDRL) in the absence of IgM testing
  • a reactive CSF non-treponemal test (RPR or VDRL) in the child
  • the child remains seropositive by a treponemal-specific test (EIA, TPPA, TPHA or FTA-Abs) at 15 months of age, and this test is confirmed by a different reactive treponemal-specific test or a reactive non-treponemal test (RPR or VDRL), in the absence of postnatal exposure to T. pallidum, including the non-venereal subspecies T. pallidum subspecies pertenue (yaws) or subspecies endemicum (bejel), or to T. carateum (pinta).

Case classification

  • Under investigation: A case that has been notified, but information is not yet available to classify it as probable or confirmed.
  • Probable: Clinical evidence and laboratory suggestive evidence.
  • Confirmed: A case that has laboratory definitive evidence.
  • Not a case: A case that has been investigated and subsequently found not to meet the case definition.

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.

[4] A stillbirth where fetal death has occurred after a 20-week gestation or in a fetus that weighs more than 500 g should be counted as clinical evidence towards a case where laboratory suggestive or definitive evidence exists.

[5] Any positive sera should be tested by serial dilution to provide an end-titre. Mother and child sera should be collected at the same time and tested in parallel. Cord blood should not be used for the investigation of congenital syphilis.

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