A follow-up study on bovine rotavirus dissemination among calves of a large dairy herd

Rotaviruses had previously been involved in lethal diarrhoea of newborn calves as well as non-lethal diarrhoea in calves aged 6 to 7 weeks in a closed dairy herd comprising 220 heads of cattle. Fifty calves born consecutively were thereafter tested at weekly intervals till 8 weeks old for diarrhoea by clinical judgement of their feces and for rotavirus excretion by ELISA tests. Serum antibodies against rotaviruses were sporadically determined by CF tests. Rotavirus was shown to persist in this herd in widely disseminated form, in seasonal waves, peaking during the second week of age. The first week of life and the third, in this order, ranked next in frequency of dissemination. Silent, non-clinical rotavirus excretion also occurred quite frequently in calves 1 to 3 weeks old. All calves examined possessed maternally-derived antibodies in their blood serum, which according to literature merely exert protective activity as long as present in the unabsorbed state in the gut lumen. Careful colostrum feeding during the first week postponed rotavirus excretion as compared to the earlier onset described in the United States, and milk replacer (devoid of antibody) fed from day 8 onward accounted for the peak of rotavirus infection in the second week of life. It proved impossible to assess the degree of rotavirus coetiology for diarrhoea observed at high frequency.

Bovine adenoviruses--IV. Two mixed antigens for routine serodiagnosis by complement fixation reaction

The frequency of bovine adenovirus infections occurring in cattle has been grossly underestimated up to the present day. Primary isolation of serotypes belonging to bovine subgroup II is cumbersome. Hardly any laboratory has used all 8 officially-recognised bovine serotypes in seroneutralisation-tests, which should be done when this type-specific method is used for serodiagnosis. The complement fixation test, known as group-reactive from human adenovirus serology, has failed to disclose the true incidence of bovine infections, as until recently the importance of a novel additional group-reactive bovine adenovirus antigen has been undisclosed. Here we describe production, composition and performance of two mixed antigens for complement fixation reactions, which take into account recent findings by our team on peculiarities of bovine adenovirus antigens. Mixed antigen 1 contains bovine serotypes 1, 2 and 3 and detects group-specific antibodies of the classical mastadenoviruses. Mixed antigen 2 contains bovine serotypes 4, 5, 6, 7 and 8 and determines group-specific antibodies against the novel paramastadenoviruses. In addition, each antigen is capable of demonstrating complement-fixing type-specific antibodies in sera against the respective types included in each mixed antigen, with a net enhancing effect produced by mixing. Use of the 2 mixed antigens promptly shows whether bovine adenoviruses, presently recognised as well as unclassified, are involved in a given outbreak of respiratory or enteric disease of cattle. If needed, the responsible type may be determined in a second step of serological investigation.

Herpesvirus strigis, a new avian herpesvirus. II. Biochemical and biophysical properties

A virus (HSIS) originating from dead owls was successfully cultivated in chicken embryo fibroblasts. Its replication was inhibited by IUDR. Tissue cultured virus proved sensitive to ether, chloroform, 0.5 per cent trypsin, and to pH levels of 4.0 or lower. Infectivity was rapidly destroyed at 56° C. Negatively stained naked virions of 100 nm average diameter were seen, and enveloped virions with 160–250 nm size. The capsid was built up of hollow cyclindrical capsomeres, arranged in equilateral triangles, carrying 5 capsomeres along each edge. Cubical symmetry and icosahedron structure yielded a total number of 162 capsomeres. All these biochemical and biophysical data lead to classification of HSIS virus into the genus herpesvirus. Biological properties described in a foregoing paper sustained such grouping, and indicated that the agent was a new avian herpesvirus for which the nameherpesvirus strigis was proposed.