Leprosy

History and context

The Karonga research programme began as a leprosy project, and was located in Karonga because of the relatively high frequency of leprosy in that population during the 1970s. Initially called the “Lepra Evaluation Project” (LEP) the project was first funded entirely by leprosy organisations, in particular LEPRA, the British Leprosy Relief Association. A major stimulus came from the IMMLEP (Immunology of Leprosy) programme of the WHO Tropical Disease Research Programme (TDR), which had developed a variety of new skin test antigens and serological assays since its inception in 1974. The LEP was in effect the global population laboratory for the new generate of diagnostic tools and vaccines.

The LEP began as a total population cohort study, with a first survey (“LEP-1”) of approximately 112,000 individuals over the years 1979 – 1984, followed by a follow-up survey (“LEP-2”) of approximately 145,000 individuals late 1985-1989. The second survey was used as the recruitment phase of a randomised controlled trial comparing one dose of BCG versus two doses of BCG versus a combined vaccine incorporating BCG + killed M leprae in prevention of leprosy and tuberculosisWidely known as the Karonga Prevention Trial (KPT), the codes were broken in 1996, revealing that each dose of BCG provided approximately 50 % protection against leprosy but not against tuberculosis.

As a consequence of this history, leprosy has been studied more thoroughly in Karonga District than in any other population of the world.

Epidemiological studies

Many aspects of M leprae infection and leprosy disease were addressed over a period of 30 years, including:

  • Evaluation of new skin tests, serological tests and PCR for M leprae infection
  • Critical analysis of sensitivity and specificity of clinical diagnostic algorithms
  • Blinded comparisons of histopathological evaluation of leprosy biopsies
  • Analysis of anatomic site distribution of leprosy lesions
  • Studies of factors for leprosy disease, including: age, sex, BCG history, household contact, housing and other socio-economic variables, HIV infection, hygiene, geography, prior sensitivity to various mycobacterial antigens, genetics
  • Evaluation of effectiveness of BCG in 1 and 2 doses, and of combined BCG + killed M leprae vaccines
  • Evaluation of effectiveness of WHO / MDT (multiple drug therapy) regimens
  • Descriptive epidemiology of leprosy associated disabilities
  • Burden of residual leprosy–associated disabilities

Patterns and trends of leprosy

More than 3000 confirmed leprosy cases were identified in Karonga District over the course of the project, Leprosy incidence and prevalence declined dramatically over the years, with 100 – 200 new cases identified per year in the 1980s declining to less than 10 per year after 2000, so that the disease has now all but disappeared from the district. It is likely that improved socio-economic conditions, an aggressive case finding and treatment programme and widespread vaccination all contributed to this trend.

Current studies (2012-2016)

We continue to follow up people with leprosy associated disabilities to be able understand the ongoing burden in the community.

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