High prevalence of tuberculosis and insufficient case detection in two communities in the Western Cape, South Africa.

Background: In South Africa the estimated incidence of all forms of tuberculosis (TB) for 2008 was 960/100000. It was reported that all South Africans lived in districts with Directly Observed Therapy, Short-course. However, the 2011 WHO report indicated South Africa as the only country in the world where the TB incidence is still rising.

Aims: To report the results of a TB prevalence survey and to determine the speed of TB case detection in the study communities.

Methods: In 2005 a TB prevalence survey was done to inform the sample size calculation for the ZAMSTAR (Zambia South Africa TB and AIDS Reduction) trial. It was a cluster survey with clustering by enumeration area; all households were visited within enumeration areas and informed consent obtained from eligible adults. A questionnaire was completed and a sputum sample collected from each adult. Samples were inoculated on both liquid mycobacterium growth indicator tube (MGIT) and Löwenstein-Jensen media. A follow-up HIV prevalence survey was done in 2007.

Results: In Community A, the adjusted prevalence of culture positive TB was 32/1000 (95%CI 25-41/1000) and of smear positive TB 8/1000 (95%CI 5-13/1000). In Community B, the adjusted prevalence of culture positive TB was 24/1000 (95%CI 17-32/1000) and of smear positive TB 9/1000 (95%CI 6-15/1000). In Community A the patient diagnostic rate was 0.38/person-year while in community B it was 0.30/person-year. In both communities the adjusted HIV prevalence was 25% (19-30%).

Discussion: In both communities a higher TB prevalence than national estimates and a low patient diagnostic rate was calculated, suggesting that cases are not detected at a sufficient rate to interrupt transmission. These findings may contribute to the rising TB incidence in South Africa. The TB epidemic should therefore be addressed rapidly and effectively, especially in the presence of the concurrently high HIV prevalence.