Tuberculosis

Description

Tuberculoisis is a general term for diseases caused by the tuberculous group of bacteria, Mycobacteria species. Mycobacterium tuberculosis, Mycobacterium bovis, Mycobacterium avium are host adapted to humans, cattle and birds respectively. All three types can produce disease in other species; Mycobacterium tiberculosis is the most host specific strain and rarely causes progresive disease in species other than humans, Mycobacterium bovis can affect a number of other species, see Bovine Tuberculosis. Mycobacterium avium is Avian Tuberculosis.

Infection can be via inhalation of infective droplets, ingestion of contaminated feed or water, and occasionally via coitus or via milk.

The primary focus of infection is determined by the route of infection. Characteristic granulomatous tubercles develop. These become nectrotic, shedding the infetcive which disseminates to other body systems initiating secondary foci.

Diagnosis

Pathology

• Grossly:
  • Yellowish spherical nodules
  • Caseous content
  • Fibrous capsule usually
• Histologically:
  • Granuloma
  • Central necrosis
  • Epitheliod and giant cells at periphery