1. The long-term effect of current and new interventions on the new case detection of leprosy: a modeling study
- Author
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J. Dik F. Habbema, Sake J. de Vlas, Egil A.J. Fischer, Jan Hendrik Richardus, and Public Health
- Subjects
Male ,Pediatrics ,Diagnostics & Crisis Organization ,Medicine ,Child ,Subclinical infection ,Diagnostiek & Crisisorganisatie ,Incidence ,lcsh:Public aspects of medicine ,trial ,protection ,Immunizations ,Anti-Bacterial Agents ,Mycobacterium leprae ,Vaccination ,Infectious Diseases ,Child, Preschool ,Chemoprophylaxis ,BCG Vaccine ,bangladesh ,bcg ,Female ,epidemiology ,Public Health ,Leprosy ,Tuberculosis vaccines ,Research Article ,Neglected Tropical Diseases ,metaanalysis ,Adult ,medicine.medical_specialty ,Tuberculosis ,contacts ,lcsh:Arctic medicine. Tropical medicine ,Infectious Disease Control ,lcsh:RC955-962 ,Chemoprevention ,Infectious Disease Epidemiology ,mycobacterium-leprae ,SDG 3 - Good Health and Well-being ,Humans ,Computer Simulation ,business.industry ,Infant, Newborn ,Public Health, Environmental and Occupational Health ,chemoprophylaxis ,Infant ,lcsh:RA1-1270 ,medicine.disease ,Surgery ,Early Diagnosis ,Contact Tracing ,Infectious Disease Modeling ,business ,BCG vaccine ,Contact tracing - Abstract
Background Although the number of newly detected leprosy cases has decreased globally, a quarter of a million new cases are detected annually and eradication remains far away. Current options for leprosy prevention are contact tracing and BCG vaccination of infants. Future options may include chemoprophylaxis and early diagnosis of subclinical infections. This study compared the predicted trends in leprosy case detection of future intervention strategies. Methods Seven leprosy intervention scenarios were investigated with a microsimulation model (SIMCOLEP) to predict future leprosy trends. The baseline scenario consisted of passive case detection, multidrug therapy, contact tracing, and BCG vaccination of infants. The other six scenarios were modifications of the baseline, as follows: no contact tracing; with chemoprophylaxis; with early diagnosis of subclinical infections; replacement of the BCG vaccine with a new tuberculosis vaccine ineffective against Mycobacterium leprae (“no BCG”); no BCG with chemoprophylaxis; and no BCG with early diagnosis. Findings Without contact tracing, the model predicted an initial drop in the new case detection rate due to a delay in detecting clinical cases among contacts. Eventually, this scenario would lead to new case detection rates higher than the baseline program. Both chemoprophylaxis and early diagnosis would prevent new cases due to a reduction of the infectious period of subclinical cases by detection and cure of these cases. Also, replacing BCG would increase the new case detection rate of leprosy, but this effect could be offset with either chemoprophylaxis or early diagnosis. Conclusions This study showed that the leprosy incidence would be reduced substantially by good BCG vaccine coverage and the combined strategies of contact tracing, early diagnosis, and treatment of infection and/or chemoprophylaxis among household contacts. To effectively interrupt the transmission of M. leprae, it is crucial to continue developing immuno- and chemoprophylaxis strategies and an effective test for diagnosing subclinical infections., Author Summary Leprosy is a contagious disease that will remain prevalent, despite the declining number of patients worldwide over the last century. With approximately 250,000 new cases detected annually, leprosy is far from being eradicated. Leprosy can be treated with drugs after disease detection. Some cases can be prevented with a tuberculosis vaccine (BCG) that cross-reacts with the bacterium responsible for leprosy, but this vaccine might be replaced in the future. Furthermore, preventive drugs can reduce the number of new cases among people in contact with infectious patients, but this strategy has not yet become established in common practice. Also, a new test is under development for the detection of infections before the appearance of symptoms. In this study, we used a computer model to assess the effectiveness of seven possible leprosy control activities. Our results showed that the decline in incidence of leprosy would slow down or halt with the introduction of a new tuberculosis vaccine that is ineffective against leprosy. However, this effect could be offset by the implementation of effective tests for early diagnosis or the routine administration of preventative drugs to contacts of patients.
- Published
- 2011