Submitted to: American Association of Veterinary Laboratory Diagnosticians
Publication Type: Proceedings
Publication Acceptance Date: 5/31/1995
Publication Date: N/A
Technical Abstract: In this report, we describe gross and microscopic lesions of diagnostic value found in fetuses transplacentally infected with PRRSV during late gestation. Sows (#1-7) free of PRRSV-specific antibody and one sow (#8) that had been previously infected with PRRSV were oronasally exposed to a PRRSV inoculum at or about 90 days of gestation (DG). One control sow (#9) was oronasally exposed to a sham inoculum at 90 DG. Sows were euthanized 21 days-post-exposure and fetuses tested for virus. Transplacental infection and gross and microscopic lesions were found in litters 1 through 7; however, no infection or lesions were found in litters 8 and 9. Significant lesions were found in the umbilical cords which ranged from segmental hemorrhagic areas 1 to 2 cm in length to a full length involvement of the cord which was grossly distended with frank hemorrhage. All live fetuses that had gross lesions in their umbilical cord were viremic and a necrotizing arteritis with periarterial hemorrhage was found in each cord by histopathological examination. This was the most consistent microscopic lesion in fetuses infected with PRRSV. Sows 1 through 7 had endometritis and myometritis of varying degrees suggesting PRRSV may induce these lesions as well. In addition, PRRSV antigen was detected in fetal lung, liver, heart, spleen, kidney and umbilical cord. Occasionally antigen was observed in cells that resembled smooth muscle cells, fibroblasts and endothelial cells. This study indicates careful gross and microscopic examination of the umbilical cord may aid in the diagnosis of PRRSV-induced reproductive failure.