Background
Leprosy is a notifiable infection of skin and nerves caused primarily by Mycobacterium leprae. In Australia, leprosy is found primarily in northern indigenous populations and immigrants from endemic regions overseas.
211,973 cases were reported globally in 2015. Prevention is based on surveillance, and treatment is based on WHO protocols of multidrug treatment (MDT) since 1995. In Australia, the trend of decreasing incidence has recently reversed, particularly in at-risk populations.
Findings
Australian National Notifiable Disease Surveillance System data show the highest four-year incidence was 1991-1994 (58 cases). By 1999-2002, the number decreased to 23. Since then, it has risen consistently: in the three years 2015–2017, 53 cases were reported, which is approaching the highest incidence.
Symptoms take 9 months to 20 years to develop. People who are infected are not treated until they show symptoms, and they are infectious until treated. Additionally, the multi-drug treatment duration is long (6-24 months), and the diagnosis carries significant stigma, regardless of effective treatment. Therefore, the best course of prevention for people in close contact to known patients may be vaccination.
There have been many attempts to develop a vaccine: from first generation Bacillus Calmette–Guérin; to second generation antigens from M. Leprae; to third generation recombinant subunit vaccine. To date, an effective vaccine has been elusive.
Conclusion
Leprosy has been controlled since the WHO-MDT initiative, but is now increasing in Australia. Development of an effective vaccine may be an effective method of infection control in Australia and in endemic areas.