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CSU 93/2011: THREE DECADES OF TB RESEARCH IN MALAWI

Wednesday, 16th of March 2011 Print

LESSONS FROM THREE DECADES’ TB RESEARCH IN MALAWI

Major messages: BCG was found protective against leprosy, but not against adult pulmonary TB. HIV has radically altered the epidemiology of TB in this rural district of northern Malawi. Without HIV, TB would likely have declined. Drug resistance remains <10 percent.

 

Full text, http://docstore.ingenta.com/cgi-bin/ds_deliver/1/u/d/ISIS/61693881.1/iuatld/ijtld/2009/00000013/00000002/art00002/33D5C50B1305352F1300005332492B9324A603582A.pdf?link=http://www.ingentaconnect.com/error/delivery&format=pdf

What has Karonga taught us? Tuberculosis studied over three decades [State of the art series. Tuberculosis. Edited by I. D. Rusen. Number 4 in the series]

Authors: Crampin, A.C.1; Glynn, J.R.2; Fine, P.E.M.2

Source: The International Journal of Tuberculosis and Lung Disease, Volume 13, Number 2, February 2009 , pp. 153-164(12)

 

 

ABSTRACT

This  paper summarizes tuberculosis research over almost 30 years in Karonga district, northern Malawi, an area typical of much rural Africa. The dominant factor has been the human immunodeficiency virus which arrived in the district about 1980, leading to an increase in TB incidence to a peak of approximate 65 smear-positive pulmonary cases per 100,000 population in 2000. Tuberculin surveys indicate annual risks of M. Tuberculosis infections of approximately 1%; thus, most of the population is uninfected and at risk of primary infection and diseases. Molecular epidemiological studies demonstrate that about two thirds of TB arises from recent infection, but recognizable recent contact is responsible for only about 10% of diseases. By 2001, 57% of TB was directly attributable to HIV, implying that it would have declined were it not for HIV. HIV infection increases the risk of TB most among young adults, and greatly increases the risk of recurrence from new infection after treatment. Mortality rtes in the HIV-infected are high, but there is no association of HIV with drug resistance. Other risk factors with relatively smaller effects include age and sex, contact, several genetic polymorphisms and area.

Neither one nor two doses of BCG vaccine provides protection against adult pulmonary TV, despite protecting against leprosy. Skin test surveys, cohort studies and comparative immunological studies with the UK suggest that exposure to environmental mycobacteria provides some protection against TB and that BCG’s failure is attributable partly to this widespread heterologous exposure masking effects of the vaccine. Drug resistance has remained constant (<10%) over more than 20 years. Immunotherapy with M. vaccae provided no benefits, but treatment of HIV-positive patients with cotrimoxazole reduced mortality. The Karonga programme illustrates the value of long-term population-based studies to investigate the natural history of TB and to influence TB control policy. Current studies focus on immunological markers of infection, disease and protection, and on elucidating the impact of antiretroviral treatment on TB incidence at population level.

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