SALMONELLA-ABORTUSOVIS EXPERIMENTAL-INFECTION INDUCED BY THE CONJUNCTIVAL ROUTE - CLINICAL, SEROLOGICAL AND BACTERIOLOGICAL STUDY OF THE DOSE-EFFECT IN FEMALE LAMBS

The aim of this work was to explore the first stages of infection with Salmonella Abortusovis after a mucosal inoculation, and to establish an experimental model limiting the bacteriological investigations to t he inoculation site. Four groups of 6 ewe-lambs were infected by the c onjuctival route with decreasing doses of Salmonella Abortusovis. The clinical and serological survey was completed by a daily bacteriologic al examination of nasal swabs and faeces. Enumeration of viable bacter ia was performed on liver, spleen, lungs and lymph nodes harvested 1, 8, and 22 d after inoculation. A rapid colonization of the cephalic ly mph nodes was observed, associated with a transient spreading to presc apular and subiliac lymph nodes without dissemination to the liver and spleen. An irregular and low level faecal excretion was associated wi th the colonization of mesenteric lymph nodes. The infection by the co njunctival route may either systematically propagated or be locally re stricted by the lymphoid system in relation to doses administered. Thi s model uses low infective doses similar to those occurring in field c onditions and offers the possibility of limiting the bacteriological c ontrol to the regional lymph nodes. It confirms that live attenuated S almonella strains may be used as vaccinal vectors by the mucosal route .