Bovine Tuberculosis

• Bovine tuberculosis is an infectious granulomatous disease caused by Mycobacterium bovis
• Bovine TB primarily affects the lungs and their draining lymph nodes but can also affect other organs depending on the portal of entry
• Infection remains subclinical for months or years until organ involvement is severe enough to cause functional impairment
• Transmission of M. bovis can occur through inhalation of aerosols, ingestion, or breaks in the skin
• Cattle shed M. bovis in respiratory secretions, feces, milk, urine, vaginal secretions, or semen
• Humans can be infected by M. bovis through ingestion of unpasteurized dairy products, aerosols, or breaks in the skin
• Inhalation of infected droplets is the usual route of TB infection, but ingestion can also occur via contaminated milk, water, or food
• Granulomas form in infected tissues, consisting of dead and degenerate macrophages surrounded by various cells
• Primary complex refers to the initial granulomatous lesions in the organ and regional lymph node
• Clinical signs of bovine TB in animals include emaciation, lethargy, weakness, anorexia, diarrhea, and fever
• Post mortem lesions in bovine TB are characterized by the formation of granulomas (tubercles) in various organs
• Diagnosis of TB involves cellular immune response, culture, molecular tests, and the intradermal tuberculin test
• Control measures for TB in production animals include test-and-cull and abattoir surveillance
• No reliable TB vaccine is available for any species due to interference with diagnostic assays
• Zoonotic potential: Members of the M. tuberculosis complex can infect humans, with zoonotic TB lesions often having an extrapulmonary location
• Global burden of zoonotic TB is underrecognized, with symptoms varying by site and treatment failures being more common in zoonotic TB