Atlas of pathology
Where: lymphatic system, lymph nodes
This is tuberculosis in pigs, due to infection with one of the Mycobacterium species, often M avium. The lymph nodes of the neck and intestines of these pigs may be slightly enlarged and firm. The surrounding tissues and the body organs of the pigs often appear relatively normal. The affected nodes have firm grey swelling, with some nodules of various sizes and yellow gritty areas. The types of Mycobacteria that affect pigs are usually the ones found in poultry and birds and from the environment, particularly the soil. The disease is not transmitted between pigs, each individual pig gains the bacterial infection from the environment or interaction with birds. Tuberculosis in pigs is therefore usually seen in smaller farms where the pigs have prolonged access to soil or chickens. On some farms, pigs may have access to infected chicken or wildlife carcase materials presented as feedstuffs. The bacteria are eaten by the pig and settle in the lymph nodes, causing the relatively moderate lesions, usually seen at slaughter. In contrast to tuberculosis in cattle, the types of Mycobacteria and tuberculosis in pigs are not usually considered a threat to humans.