The effects of intra-amniotic inoculation of Hemophilus somnus on the bovine fetus and dam.

The injection of three strains of Hemophilus somnus into the amniotic cavity of pregnant cows produced death of the fetus and abortion followed by retention of the placenta. H. somnus was recovered readily from the placenta but less so from the fetus. Lesions in the placenta were conspicuous in arteries and somewhat resembled vascular lesions observed in septicemic H. somnus. H. somnus was recovered from the maternal circulation in several infected cows. Clinical signs included fever, irritability, lameness, and vulvar discharge, but no cows died. The organism was recovered for prolonged periods in cervicovaginal mucus and urine after remission of clinical signs. This may be a means of spread of infection.