Despite it being completely curable, there are still over 200,000 cases of leprosy diagnosed every year and potentially many more falling under the radar. Leprosy is a mildly contagious disease and is transferred by droplets from the nose and mouth during close and frequent contact with untreated patients.
An essential step towards Zero Transmission is to improve diagnostics tools and to make that diagnosis as early as possible. As ancient as leprosy is, we are still not adept at spotting it and in some places in the world feathers are still used to diagnose the disease.
“Leprosy is mainly diagnosed by expert clinicians using defined criteria, along with the use of slit-skin smears and biopsies,” Paul Saunderson, the Medical Director at American Leprosy Missions and chair of ILEP’s technical commission, says. “As the prevalence of the disease is decreasing, clinical expertise is diminishing.”
This diminishing expertise prolongs diagnosis, Saunderson says, allowing the disease to set in and spread further: “So, efforts to achieve Zero Transmission are undermined.”
Creating a Zero Transmission Programme
For Saunderson, any programme to achieve Zero Transmission needs three things: (i) early diagnosis and prompt Multi Drug Therapy for all patients, (ii) contact tracing and post-exposure prophlyaxis (PEP) for those who have been in contact with newly diagnosed patients, and (iii) strict epidemiological surveillance and systems to monitor progress.
“An ideal test would identify M. leprae infected individuals at risk of developing disease and/ or who contribute to transmission. However, given the challenge of developing such a test, a two-step approach might prove to be a more expeditious strategy.” This test, he continues, would firstly help health care workers in their clinical diagnosis and decision-making process for treatment. Another test would identify the infected individuals.
What needs to be available is a point-of-care, non-invasive test for leprosy diagnostics. “This would require national leprosy programmes to intensify their surveillance systems in order to trigger prompt and targeted testing of high-risk clusters,” Saunderson says. “Introducing a new diagnostic test could certainly help to achieve Zero Transmission, but it would require a strong commitment from policy makers and donors.”
“In the absence of a perfect test to detect all leprosy infected individuals, a diagnostic test to confirm leprosy at an early stage among symptomatic patients would be an acceptable and useful short-term compromise.” In the meantime until such a “perfect test” is available, Saunderson believes PEP has the possibility of minimising transmission by reducing the number of new cases.