Lymphadenitis:

• Lymphadenitis is inflammation of lymph node. Lymph nodes can also get enlarged through infiltration of neoplastic cells.
• Enlarged peripheral lymph nodes causes visible and palpable swellings and in some cases obstruction to lymphatic drainage and subsequent local edema.
• Enlargement of internal nodes may cause obstruction of the esophagus or pharynx, trachea or bronchi.
• Lymphadenitis occurs as a result of infection or of neoplastic invasion.

Etiology:

• Corneybacterium pseudotuberculosis causes ulcerative lymphangitis in horse and caseous lymphadenitis in sheep.
• Bacillus anthracis also causes lymphadenitis
• Strangles in horse
• Cervical adenitis caused by Streptococcus, Actinomyces pyogenes and Pasteurella multicoda
• Mycobacterium tuberculosis, Mycobacterium avium, Mycobacterium bovis
• Tularemia, infection with Francisella tularensis, in tick-infested sheep
• Tick pyemia associated with Staphylococcus aureus in sheep infested with the tick Ixodes ricinus.