DISTRIBUTION OF CYTOPATHIC AND NONCYTOPATHIC BOVINE VIRAL DIARRHEA VIRUS-ANTIGENS IN TISSUES OF CALVES FOLLOWING ACUTE EXPERIMENTAL-INFECTION

The distribution of cytopathic and noncytopathic biotypes of bovine vi ral diarrhea virus (BVDV) in the tissues of colostrum-fed and colostru m-deprived calves was investigated. Colostrum-fed (group A) and colost rum-deprived (group B) calves were experimentally infected with the BV DV isolate 80/1, which contains both BVDV biotypes. Colostrum-deprived calves were also experimentally infected with a noncytopathic BVDV (g roup C) or with a cytopathic BVDV (group D) cloned from the 80/1 isola te. All calves were sequentially euthanized, and a wide range of tissu e samples were processed for immunofluorescent and virus isolation stu dies. In group A, consistent immunofluorescent staining for BVDV was d etected in vascular smooth muscle of numerous blood vessels in the tis sues examined, mainly at 11 and 13 days postinoculation. A predominanc e of samples containing cytopathic BVDV was observed in the calves of this group, following virus isolation studies. Both cytopathic and non cytopathic BVDV were detected/recovered from a larger range of specime ns in the calves in group B than from the calves in group A. In the ca lves in all the experimental groups, large amounts of BVDV antigen wer e detected mainly in tissue samples from the lymphoid and gastrointest inal systems, whereas only minimal amounts of BVDV were detected in th e respiratory tract. Abundant noncytopathic BVDV antigen was also dete cted in pituitary gland and in Langerhans islets in pancreases of colo strum-deprived calves infected with the cloned noncytopathic BVDV. Non cytopathic BVDV was isolated from a wider range of tissues from calves in group C than in the colostrum-deprived calves infected with both B VDV biotypes. A cytopathic BVDV was isolated/detected in retropharynge al, mesenteric, and abomasal lymph nodes and in thymus of 2 calves in group C. Cytopathic BVDV was detected/isolated mainly from mesenteric lymph nodes and Peyer's patches of the calves in group D.