Abortion, Stillbirth, Early Death of Young in Rabbits by Listeria monocytogenes. I. Ocular Instillation.

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Abstract
When Listeria monocytogenes was instilled into the conjunctival sac of 13 rabbits at the end of 2 weeks of gestation, 5 aborted and survived; 2 aborted and died; 2 died before abortion; 3 aborted and were sacrificed; and one was sacrificed before abortion. Similar exposure of 7 does 4-2 days prepartum resulted in intrauterine infection of the young which were either stillborn or died within the first 8 postnatal days. Metritis was the most consistent lesion in necrop-sied does. Focal hepatic necrosis was most consistently observed in aborted fetuses and new-born. L. monocytogenes was cultivated readily from the uterus of necropsied does and from the cotyledons, amniotic fluid, liver, and stomach contents of the fetuses and from the liver and stomach contents of the young. Of 3 does rebred 8 weeks postabortion and reexposed 2 weeks prepartum, one aborted and died; one died; and one delivered a normal appearing litter. Two does rebred 17 days postpartum aborted spontaneously during the 3rd week of gestation and L. monocytogenes was isolated from all the aborted fetuses and membranes. Does rebred 17 days or more postpartum but not reexposed usually gave birth to normal appearing litters. Twelve nonpregnant does failed to show symptoms suggestive of generalized infection following a similar exposure. The results indicated that the conjunctivitis which follows ocular instillation is not a local reaction, but will consistently infect the uterine contents of the pregnant rabbit. Obliquely transmitted light and a scanning microscope proved an excellent technique for identifying colonies of L. monocytogenes made directly from grossly contaminated material.