A. Schwers

Comparison of the effect of trisodium phosphonoformate on the mean plaque size of pseudorabies virus, infectious bovine rhinotracheitis virus and pigeon herpesvirus.

Abstract The effect of various concentrations of trisodium phosphonoformate on the titre and the mean plaque size of pseudorabies virus (SHV), infectious bovine rhinotracheitis (IBR) virus and pigeon herpesvirus (PHV) was studied. Phosphonoformate significantly reduced the mean plaque size of all three viruses whatever the concentration used. However, an increase of the concentration of phosphonoformate over 100 μ m per ml in the overlay medium did not further reduce the mean plaque size of PHV. Phosphonoformate also produced a decrease in the titre of the three viruses at the highest concentration. SHV was the most susceptible to the effect of trisodium phosphonoformate and PHV was the least susceptible. This finding might be of significance for a possible clinical application in the treatment of local lesions produced by PHV infection.

Propagation of bovine rotavirus by young dogs

Abstract Ten young dogs were experimentally infected twice with different isolates of bovine rotavirus and 2 uninfected dogs were kept in contact with them. None of the animals developed diarrhoea, but all of them excreted rotavirus in their faeces over a period of up to 10 days after each inoculation, as shown by counterimmunoelectro-osmophoresis and virus isolation. Dogs may thus play a role in the epizootiology of rotavirus diarrhoea in calves. Seroconversion occurred in 6 of the 10 infected dogs but in neither of the 2 contact controls.

Susceptibility of different strains of pigeon herpesvirus to trisodium phosphonoformate.

The susceptibility to trisodium phosphonoformate of five strains of pigeon herpesvirus (Pigeon Herpesvirus 1, PHV) was compared by measuring the mean plaque size variations in the presence of different concentrations of the compound. Significant differences in their susceptibility to phosphonoformate were observed, but none of them was found to be naturally resistant. This finding may be of significance for a possible clinical application in the treatment of pigeon herpesvirus infection.

Comparison of bovine rotavirus strains by plaque assay

Abstract Using plaque assay on MA 104 cells, four strains of bovine rotavirus were compared: the attenuated American strain NCDV, and three virulent strains isolated in Canada (PQ) or in Belgium (S14 and S 77). The attenuated strain (NCDV) formed smaller plaques than the three others. The plaque size may thus be used as a marker for this strain. The Belgian strain S 77 formed the largest plaques and no significant differences could be found between the Canadian strain PQ and the second Belgian strain S 14. On BSC-1 cells, the Canadian strain PQ formed much smaller plaques than on MA 104 cells.

Prevalence of antibody to rotavirus in Moroccan cattle

A serological survey was carried out in order to determine the prevalence of antirotavirus antibodies in Moroccan cattle under different management conditions. From the 493 serum samples examined, 325 (65.9%) were found positive, using a counter-immunoelectroosmophoresis technique. Animals of indigenous breed coming from farms with rapid turnover or large number of animals, or having frequent contacts with imported cattle, had a higher rate of seropositivity; however, positive sera were also found in cattle from small farms in remote areas, showing that rotavirus infection is ubiquitous in that country. No relationship was found between the prevalence of anti-rotavirus antibodies and the frequence of calf diarrhoea. The percentage of seropositive animals in a herd has to be considered as an epidemiological indicator.

Detection of rotavirus in faecal specimens with a monoclonal antibody enzyme-linked immunosorbent assay: Comparison with polyclonal antibody enzyme immuno-assays and a latex agglutination test

Abstract Monoclonal antibodies have been produced against the 81/36F strain of rotavirus. One of them, was chosen as diagnostic reagent: it showed high ELISA reactivity with all the bovine, human and porcine rotavirus strains tested and reacted with VP6, structural protein product known to support the common rotavirus antigen. A sandwich ELISA procedure using the chosen monoclonal as “capture and detecting” antibody was performed to detect rotavirus in faecal samples from experimentally inoculated newborn calves: it always gave a negative response with meconium and a positive response for the stool specimens which rotavirus have been isolated. This assay was compared with Enzygnost and Slidex Rota Kit tests and with a non-commercial sandwich ELISA test using polyclonal antibodies: it showed more sensitivity than the agglutination test and was as sensitive as the other two tests to detect rotavirus in routine diagnostic material. The test evaluated showed no equivocal results.

Studies on interferon in the bovine species : biological and biochemical effects

In 1982, our group obtained the first evidence for the efficiency of interferon as an antiviral in cattle (1). In view of its importance for the veterinary field, this successful achievement, using on the basis of the rational short cut we proposed (2) the only cloned interferon available in sufficient quantity at this moment (Hu IFN α2), prompted us to further investigate this model on a fully quantitative basis (3,4) and to evaluate the action of interferon on other viral infections of economical importance for breeders.

Antiviral Action of Interferon in the Bovine Species: Study In Vitro and In Vivo

Awaiting a multipotent antiviral vaccine preparation, perhaps a feasible goal for the future, there is still at the present time, we believe, enough room left for alternative ways to control viral diseases. Given the recent developments of bacterial production of interferon, the cost/benefits ratio of its possible use as antiviral has significantly increased. There is no more objective reason at this time to limit the investigations using interferon exclusively to the field of human health. Indeed, considerable economical interest could reside in an efficient way to control domestic animal viral diseases. We have undertaken the present study to evaluate interferon activity in the bovine species. As enough bovine interferon cannot be obtained for this purpose using our bovine cell system, we decided to use bacterially produced human interferon (Hu-IFNα2). It is readily available now and has been provided to us by Dr. C. WEISSMANN (Zurich University). This interferon was shown to cross the species barrier, using in vitro cell systems.