Experimental Brucella abortus induced abortion in a llama: Pathologic effects

Brucella abortus infection has not been documented in llamas. This report d escribes the abortion of the only pregnant animal in a group of 12. The lla ma was infected by inoculating 1 x 10(8) viable B. abortus organisms into t he conjunctival sac. Forty-three days postinfection, the llama aborted a fe tus of approximately 8 months gestational age. Brucella organisms were isol ated from the placenta and all fetal specimens examined. These organisms we re also isolated from the dam's mammary gland and numerous lymph nodes when the llama was necropsied 42 days later. Microscopically, there was a moder ate, multifocal, lymphocytic and histiocytic, subacute placentitis with mar ked loss of trophoblastic epithelial cells. The superficial chorioallantoic stroma contained abundant necrotic and mineralized debris as well as numer ous swollen capillaries protruding multifocally from the denuded surface. I mmunohistochemistry revealed that these capillaries, as well as sloughed an d intact trophoblasts, were expanded by large numbers of Brucella organisms . Brucellar antigen was also detected in occasional macrophages in the feta l kidney and lung. Ultrastructurally, bacteria labeled by an antibody-based colloidal gold procedure were located within degenerate capillaries, withi n necrotic leukocytes, and extracellularly in the placental stroma.