Bovine Tuberculosis Surveillance System Evaluation, Greater-Accra Region, Ghana, 2006-2011

Bovine tuberculosis (bTB) is a chronic, zoonotic, multi-species disease of cattle caused by Mycobacterium bovis. In developed countries, effective surveillance and enforcement of regulations on bTB control resulted in significant reduction of infections in cattle and hence, humans. However, in developing countries, weak surveillance systems affect accurate and timely reporting of bTB in humans and cattle. In Ghana, transhumance movement of cattle increases the risk of bTB importation and spread, however, the extent to which surveillance detects bTB is unknown. We therefore evaluated the bTB surveillance system in the Greater-Accra Region to determine its performance and assessed its attributes.

We interviewed stakeholders, and reviewed bTB surveillance data for all ten districts in the region from 2006-2011 using the CDC Guidelines for Evaluation of public health surveillance systems.

From 2006-2011, bTB was suspected in 284/244,576 (0.12%) cattle slaughtered, of which 7/284 (2.5%) were submitted for laboratory confirmation and all tested positive. Predictive value positive was 100%. There is no standard case definition which guides bTB detection. Fifty percent of carcasses slip through inspection, and confirmed cases are not traced back. There were 99/284 (34.9%) condemnations from suspected carcasses and 57/97 (58.8%) from positive reactors from screening. Ninety percent (9/10) of districts submitted reports late to the region whereas representativeness was 30%. Regional and district data were manually stored with no electronic backups. The region's cattle population is unknown.

Although the bTB surveillance system is sensitive, it is under performing, and the possibility of bTB transmission from cattle to humans is high.