COMPARATIVE HISTOPATHOLOGY OF DRAINING LYMPH-NODE AFTER INFECTION WITH VIRULENT OR ATTENUATED STRAINS OF SALMONELLA-ABORTUSOVIS IN LAMBS

Histological responses to the early phase of infection were compared i n parotid lymph nodes of lambs infected by the subcutaneous route into the right eyelid with either a virulent or an attenuated strain of Sa lmonella abortusovis. The right parotid lymph nodes showed a massive P MN infiltration for the first days of infection for both strains. From day 6, the infected lymph nodes developed a lymphoid hyperplasia with prominent germinal centers independent of strain type. The virulent s train of S. abortusovis induced focal lesions in 2 out of 6 lambs necr opsied on days 6 and 10, and provoked a systemic infection evidenced b y the regular colonization of spleen on day 6. In contrast, no focal l esion and a restricted bacterial dissemination were observed in lambs infected with the vaccinal strain.