Research reaffirms bovine TB's threat to humans, animals, and to international trade

As part of his doctoral research at The Norwegian School of Veterinary Science, Demelash Biffa has carried out extensive field and laboratory work on bovine tuberculosis (TB) in Ethiopia since 2007. The main aims of his study were to investigate risk factors associated with prevalence of the disease and to discover the molecular genetic characteristics of mycobacteria, which cause serious pathologic lesions in cattle. The work has led to the development of a new numeric expression approach known as Spoligotype Evolutionary Index (SEI).

Since Antiquity, tuberculosis has been one of the most ravaging and deadly diseases in both animals and humans worldwide. The main causative agents are Mycobacterium bovis (M. bovis) and Mycobacterium tuberculosis (M. tuberculosis) respectively in animals and humans, though humans are highly susceptible to the bovine strain.

In Ethiopia, bovine TB remains a major threat to animal and human health and an obstacle to international trade. Many aspects of the epidemiology of the disease, particularly of the causative agent M. Bovis, are not known.

Using molecular methods, Biffa has shown that TB in cattle is caused by a heterogeneous population of M. bovis. Some diseased animals were found to harbour multiple genotypes, indicating a high degree of infection pressure. This finding will have useful implications for any livestock vaccination program, as it appears that prior exposure to the pathogen may not provide sufficient resistance to the disease in some animals. This revelation is likely to challenge the paradigm of monoclonal infection of TB recognized in humans, but not yet in animals.

Biffa's research reaffirmed that TB in cattle poses a major threat to humans, animals, and to international trade. The thesis sets out recommendations for policy formulation with a view to achieving proper disease surveillance and control programmes in Ethiopia.

Demelash Biffa presented his doctoral thesis to the public on 7^th December 2010 at The Norwegian School of Veterinary Science (NVH). The title of his thesis is "Epidemiological and Molecular Genetic Studies of Mycobacterium bovis Infections in Cattle in Ethiopia".