Ovine and Caprine Tuberculosis – NAVLE Study Guide

Overview and Clinical Importance

Tuberculosis (TB) in sheep and goats is a chronic, granulomatous, zoonotic disease caused by members of the Mycobacterium tuberculosis complex (MTBC), primarily Mycobacterium bovis and Mycobacterium caprae. While cattle remain the primary reservoir, small ruminants can serve as maintenance hosts and pose significant zoonotic risks to humans through unpasteurized milk and direct contact. TB in small ruminants is increasingly recognized, especially in Mediterranean countries and regions where mixed farming with cattle occurs.

The disease primarily affects the respiratory tract (lungs and mediastinal lymph nodes) but can also involve the alimentary tract and mesenteric lymph nodes. Goats are highly susceptible and can develop extensive pulmonary disease with liquefactive necrosis and cavitary lesions, similar to human TB. Sheep were historically considered resistant but are now recognized as fully susceptible and can maintain infection in mixed herds.

Etiology

Causative Agents

The Mycobacterium tuberculosis complex (MTBC) includes several species capable of causing TB in sheep and goats: