Review on Bovine Tuberculosis

Bovine tuberculosis (BTB) is a chronic infectious disease caused by Mycobacterium bovis. This disease is widely distributed throughout the world and mainly affects animals with occasional human involvement. BTB can have an impact on the national and international economy, affects the ecosystem via transmission to wildlife and is of public health concern due to its zoonotic potential. It is primarily of economic importance as it can have a considerable direct effect on milk and meat production and animal reproduction. Although still present in some industrialized countries, BTB today mostly affects developing countries lacking the resources to apply expensive test and slaughter schemes. In Africa, the disease is present virtually on the whole continent; however, little accurate information on its distribution and prevalence is available. It is a chronic, generally respiratory disease, which is clinically difficult to diagnose although emaciation, loss of appetite, chronic cough and other signs of pneumonia could be symptoms developing at relatively late stages of the infection in cattle. Its pathology is characterized by the formation of granulomatous lesions, which can within the course of the disease regress or exhibit extensive necrosis, calcify or liquefy and subsequently lead to cavity formation. During meat inspection procedures on cattle carcasses in slaughterhouses, tuberculous lesions are primarily found in the upper and lower respiratory tract and associated lymph nodes. However, the bacteria can also develop a systemic infection, disseminate within its host and affect other organs. Aerosol exposure to M. bovis is considered to be the most frequent route of infection in cattle, but infection by ingestion of contaminated material may also occur. However, M. bovis infection in humans can occur through the consumption of contaminated raw or undercooked dairy and/or meat products; meanwhile occupational infection may occur due to exposure through airborne infection among farmers, veterinarians and slaughterhouse workers. Identification of M. bovis by culture, molecular techniques and biochemical methods is important for definitive diagnosis. Evaluations of antemortem tests for the diagnosis of BTB in Africa are scarce but a prerequisite to identify appropriate tools for future disease control programs. Control and prevention of the disease is vaccination and proper management of animals and humans environment.