Each year thousands of cattle are slaughtered to control the spread of bovine tuberculosis. New research reveals that testing misses many animals harbouring the disease and shows that large herds are particularly vulnerable to rapid transmission.
A team of scientists has used mathematical tools to develop models for estimating the efficiency of cattle-based controls for bovine tuberculosis (bTB). These models will help policy-makers to understand, and thus to control, a disease which costs the UK taxpayer around £91 million per annum for testing, slaughter of animals and compensation to farmers.
The models built by the team represent an advance over previous models as they are informed directly by extensive data on reported incidence and spread of the disease, rather than expert opinion. Importantly, they provide a first estimate of the quantity of infection missed by cattle testing and the contribution of this hidden burden of infection to the persistence of bTB within herds.
Applied to recent data, the models suggest that around one in five of British herds that have been cleared of restrictions, following testing for bTB, may harbour the infection. It also points to a higher incidence, and faster spread, of the disease in large herds.
The Defra-funded research was undertaken by a cross-disciplinary group of experts at the Department of Veterinary Medicine, University of Cambridge, and the Animal Health and Veterinary Agency. It was led by Dr Andrew Conlan, a researcher in Cambridge’s Disease Dynamics Group, who specialises in mathematical modelling and also works on the spread of childhood diseases.