Experimental fetal challenge using type II bovine viral diarrhea virus in cattle vaccinated with modified-live virus...

Nineteen open heifers or cows were vaccinated 45 days prior to breeding with a modified-live bovine viral diarrhea virus (BVDV) vaccine. An additional six animals were not vaccinated and served as controls. All 25 animals were estrus-synchronized and bred. At 75 days of gestation, the 25 pregnant animals were experimentally infected with a type II isolate of BVDV by intranasal inoculation. At 75 days after inoculation, the animals were euthanized and each fetus was removed and retained for sampling. Virus isolation was accomplished from fetal tissues (spleen, thymus, and small intestine). Type II BVDV was isolated from the fetuses collected from all six unvaccinated control animals and from eight of 19 fetuses from vaccinated animals, which were determined to be persistently infected following experimental challenge.