The outbreak of infectious abortion in swine, probably the first reported from the eastern United States, was associated with a strain of Bacillus abortus growing rapidly on ordinary nutrient agar slopes without seal and presenting certain slight pathological deviations from the bovine form of disease in guinea pigs such as the occurrence of necrotic, suppurating foci in spleen and lymph nodes. Agglutination tests, comprising both cross-agglutination and absorption procedures failed to distinguish the strain from the bovine type. The gross appearance of the fetuses from this outbreak was normal. The shreds of placentas obtainable indicated slight erosion of the chorionic epithelium and some exudation. The specific bacilli were quite widely disseminated in the tissues of the fetuses. The pathogenic action of this swine strain on guinea pigs was evidently much feebler than that of most earlier swine strains as reported and it approached more closely that of bovine strains. The culture fed to a pregnant sow failed to produce abortion, possibly because of the advanced stage of pregnancy. The organism was not recovered from the uterus but was found in the sow's milk.

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