Atlas of pathology
Where: skin and subcutaneous tissue
Differential diagnosis: Anthrax
This lesion is the typical presentation in pigs of the ancient animal disease known as anthrax, caused by the large bacterium Bacillus anthracis. Affected pigs are usually older outdoor pigs, which are dull, not eating, with a firm, hot and painful swelling across their throat, neck and lower face. At autopsy, the neck and throat have firm gelatinous oedema fluid, with extensive infiltration of neck and jaw tissues with clear bloody wine-like fluid and gelatinous material. The local lymph nodes are greatly enlarged and oedematous, whereas internal organs including the liver and spleen appear relatively normal. It is important to confirm any suspicious deaths by staining and examination of dry smears of the lymph node and dark fluids in the neck. This smear diagnosis is often difficult in pigs, so it is also important to culture the lymph nodes. Anthrax bacteria occur in the soil only in defined endemic regions, so unless pigs are raised outdoors in those areas, the disease is rare. However, when it is does occur, it is usually a major dramatic episode, because of the strong ability of anthrax to cause public fear in humans. It is often difficult to easily dispose of affected pigs in a practical manner. In general, they should be destroyed on site by incineration.