Pathologic and Immunologic Responses of the Fetal Lamb to Brucella ovis

Open Access
Publisher Website
Google Scholar
Abstract
Ewes were exposed to live Brucella ovis either by the intrauterine or the intraconjunctival routes prior to breeding, at breeding and at various stages of gestation. Serological and immunochemical analyses were performed on all ewe and lamb sera and gross and microscopic examinations were made of fetuses. Infections of fetuses in the ewes exposed intraconjunctivally were confined to those groups exposed between 3 and 12 weeks post breeding. Intrauterine exposures indicated (1) that the organism does not appear to remain in the nonpregnant uterus for any extended length of time, (2) probably causes the death of the ovum and embryo, and (3) fetuses of 6 weeks of gestational age are able to withstand the microbial invasion for extended periods of time. All fetuses exposed in utero from the sixth post breeding week to term were infected, as determined by immunological, bacteriological and pathological examinations. Regardless of the route of inoculation, lesions of the infected fetuses were found in the placentas, lungs, lymph nodes, kidneys, livers and intestines. Alterations in the spleen were limited to the formation of follicles with secondary centers and increased RE activity in the cords of the red pulp. Brucella ovis was recovered most frequently from the lungs and occasionally from the abomasums and a spleen. All but one of the infected fetal lambs had elevated gamma globulin levels and complement fixation titers for Brucella ovis.