VIROLOGICAL AND PATHOLOGICAL FINDINGS IN SHEEP FETUSES FOLLOWING EXPERIMENTAL-INFECTION OF PREGNANT EWES WITH CYTOPATHOGENIC-BOVINE-VIRUS DIARRHEA VIRUS

Eighteen pregnant Merino ewes were inoculated intravenously between da ys 65 and 68 of gestation with the unpurified cytopathogenic (cp) bovi ne virus diarrhoea virus (BVDV) strain Indiana (experiment I). In expe riment II, three were ewes were inoculated with the same virus after t wo successive plaque isolations in order to compare its pathogenicity for the fetus with special regard to lesions in the fetal brain. In ex periment I, fetal blood and tissue samples, allantoic fluids and place ntomes were collected sequentially between 10 and 80 days post-inocula tion (p.i.). BVDV was recovered from 6 of 19 fetuses examined during t he first 3 weeks after inoculation. From fetuses sampled between 30 an d 50 days p.i. virus was isolated from three cases only, and from 60 d ays p.i. onwards virus was no longer recovered. BVDV was longer detect ed in the allantoic fluid than in fetal tissues and continued to be pr esent until 80 days post-inoculation. From tissue samples of two fetus es of experiment I, only non-cytopathogenic BVDV was isolated, whilst samples from seven fetuses contained the cp BVDV biotype as revealed b y an immunoplaque assay. The cp biotype was also isolated from placent omes. In experiment II, virus was not isolated from any of the tissue samples of two living fetuses collected at 67 days post-inoculation. I n both experiments, cp BVDV was recovered from allantoic fluid samples . In contrast to the developing fetal brain, other tissues or organs s eemed to be less vulnerable to the cp BVDV strain Indiana. The partial purification of this virus strain did not affect its pathogenicity fo r the brains of the developing fetuses.