Diagnosis of active syphilis

Syphilis cases are on the rise. Among people 15 to 49 years old, there are 8 million cases, most in low- and middle-income countries. Syphilis can be transmitted to the foetus in pregnant women or at birth. It causes severe complications and death. Syphilis diagnosis is highly complex. Point-of-care diagnostics are urgently needed to identify infectious cases and distinguish them from previously treated cases.

Objective

We aim to:

• develop a point-of-care diagnostic assay for active syphilis and distinction from past-treated syphilis. This will result in improved screening of people at risk of acquiring syphilis, such as men who have sex with men and pregnant women. 
• transform syphilis management globally and contribute to the World Health Organization’s goal: the triple elimination of HIV, hepatitis B and syphilis in pregnant women.

Timeline 

2022–ongoing.

Approach 

We’ve developed a rapid, simple-to-use point-of-care diagnostic test using finger prick blood. It provides a result within 15 minutes. The result indicates whether a person has active syphilis and should be prioritised for further testing and antibiotic treatment.

Our test is amenable to self-testing as well as use by health care professionals. It has been licensed to Atomo Diagnostics. The test is adaptable to ELISA and bead-based assays for use in laboratory settings and serosurveillance.  

Community impact

In 2022, the World Health Organization (WHO) reported that there were:

• 8 million new cases of syphilis among people 15-49 years old 
• around 700,000 cases of congenital syphilis, leading to 150,000 early foetal deaths and stillbirths and 70,000 neonatal deaths.

Reference: respective Global Health Sector Strategies on HIV, viral hepatitis and sexually transmitted infections for the period 2022-2030 (GHSS).

In Australia, syphilis case rates have doubled between 2015 and 2022. There were 6600 notifications in 2023, 82% in men who have sex with men in urban areas. In rural areas, Aboriginal and Torres Strait islander people represent 93% of cases. Globally, in 2022, 700,000 cases of congenital syphilis were reported. In some countries, congenital syphilis rates have double in the past 5 years. 

Congenital syphilis can cause miscarriage, stillbirth, premature birth and lifelong health issues for the baby. While treatment of syphilis requires a single injection of long-acting penicillin, antibiotic-resistance has not yet been reported as a problem.  

Most syphilis-infected individuals require two tests to distinguish current active infection from a previously treated infection. This includes an initial screen to report the presence of antibodies. It also includes a confirmatory test to determine if the syphilis infection is current and requires treatment. 

Alternatively, if sores are present, a PCR test can be used to diagnose syphilis. The tests generally occur in a centralised laboratory. This can lead to delays in treatment and loss to follow up.

In resource-poor settings or clinics without follow-up capabilities, single tests are often used and there is a potential for over-treatment. An example is treating people with past-treated infections who are suspected to have active syphilis.

In some countries, antibodies to the closely related Treponemal species, which causes yaws, can cross-react with syphilis in point-of-care tests. This can lead to over-diagnosis of syphilis and over-use of antibiotics.

Our test aims to provide new pathways for the detection of cases of syphilis globally and prioritisation of people for antibiotic treatment. Improved detection will lead to a reduction of community transmission syphilis and contribute to the WHO goals of triple elimination. 

PCT/AU2025/050155: ANTIGEN COMBINATION AND METHODS AND USES THEREOF

• Priority date: 23/2/2024
• Filed: 23/2/2025
• Inventors: Drummer, Zheng, Williams