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.

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.

Propagation of bovine rotavirus by young dogs.

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.

Protection of cattle from infection with vaccinia virus by bovine interferon alpha C.

The efficacy of bovine interferon alpha C as an antiviral compound was evaluated in calves infected with vaccinia virus. Calves treated with the interferon did not develop characteristic vaccinia lesions, demonstrating a clear protective effect of treatment. The only side effect observed was hyperthermia. After intramuscular injection, interferon appeared quickly in the blood and was cleared within 24 hours. The in vivo antiviral activity of bovine interferon alpha C was confirmed by its ability to induce 2'5' A synthetase, an enzyme implicated in the antiviral state, in lymphocytes.

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.

Analysis of genetic variation in the Belgian Blue cattle breed using DNA sequence polymorphism at the growth hormone, low density lipoprotein receptor, alpha-subunit of glycoprotein hormones and thyroglobulin loci.

New DNA sequence polymorphisms were identified at four bovine autosomal loci: growth hormone, low density lipoprotein receptor, alpha-subunit of glycoprotein hormones and thyroglobulin. Assuming independent assortment between these polymorphisms, the probabilities to be heterozygous at these four loci are 0.48, 0.36, 0.10 and 0.77 respectively, within the Belgian Blue Cattle breed (BBCB). Nucleotide diversity was estimated, showing that animals from the BBCB are heterozygous for 1/1450 nucleotides, a value significantly lower than the 1/500 value found in man. Moreover, we have estimated that the mutation rate at the cytosines of CG dinucleotides is about 10 times higher than that for other nucleotides.

Propagation of bovine rotavirus by cats and dogs.

SPF cats were experimentally infected orally with bovine rotavirus. All of them excreted virus over a period of at least two weeks after inoculation. Seroconversion was observed after one week for all the animals, but it did not stop viral excretion or prevent further excretion of the same or another rotavirus strain given later. Cats or dogs kept in the same cage as inoculated animals became infected and excreted virus, but seroconversion was not observed in these contact animals. None of the animals developed diarrhoea during the experiment. Cats are thus able to multiply bovine rotavirus, and transmission of this virus occurs between cats or between dogs and cats. Therefore, cats, like dogs, may play a role in the epizootiology of rotavirus infection in calves.

In vivo and in vitro effect of acyclovir on pseudorabies virus, infectious bovine rhinotracheitis virus and pigeon herpesvirus.

The effect of various concentrations of acyclovir on the mean plaque size of pseudorabies virus (SHV), infectious bovine rhinotracheitis virus (IBR virus) and pigeon herpesvirus (PHV) has been studied. Acyclovir significantly reduced the mean plaque size of SHV and PHV, whereas IBR virus was less affected and did only show a reduction of the mean plaque size at the highest concentration of acyclovir used (1000 microM). In vivo effect of acyclovir was tested using pigeons and budgerigars experimentally infected with PHV and rabbits experimentally infected with a very low dose of SHV. Intramuscular injections of acyclovir (100 mg/kg/day; three injections/day) did not prevent the appearance of clinical disease in infected pigeons nor did reduce the level of viral excretion. The same treatment applied, as for the pigeons, before infection protected most of the budgerigars as long as they were treated, but most of them died soon after the end of the treatment. Only one rabbit was protected by the treatment. SHV was recovered in the lung of only one of the treated animals, whereas it was isolated in the lungs of each control animal.

[Attempt at the experimental reproduction of rotavirus diarrhea in newborn calves deprived of colostrum]. / Tentative de reproduction expérimentale de la diarrhée à rotavirus chez des veaux nouveau-nés privés de colostrum.

Colostrum-deprived newborn calves were orally inoculated with different doses of cell-culture bovine rotavirus or with bacterium-free filtrates of calf stools containing rotavirus. None of the animals that received high doses of cell-culture rotavirus developed diarrhoea or any other clinical sign, although all of them excreted virus for several days and produced specific antibodies; calves inoculated with lower doses of cell-culture virus or with stool filtrates showed a transient diarrhoea 48 h after inoculation. Such paradoxical results might be due to a phenomenon of interference, as bovine rotavirus is susceptible to interferon. In experimental conditions, rotavirus produces only a mild and transient diarrhoea: this contrasts with the situation observed in farms, where that virus may provoke important problems. In association with the virus itself, numerous other factors such as the environmental conditions or the response of the calf to the infection also play a role in the evolution of the disease.

Interferon response in colostrum-deprived newborn calves infected with bovine rotavirus: its possible role in the control of the pathogenicity.

Colostrum-deprived newborn calves were experimentally infected with cell-culture rotavirus. A similar process of infection was observed when the animals were inoculated immediately after birth or at the age of three days, with a corresponding delay in the onset of virus excretion and interferon production in the later case. With high doses of virus, interferon was produced very early and no symptoms were observed. With lower doses of virus, interferon production was delayed and preceded by a severe but transient diarrhoea. In all cases, several waves of interferon production were observed. Our data indicate that interferon plays an important role in the control of viral diseases in calves and in their natural recovery.

Linkage relationships among 20 genetic markers in cattle. Evidence for linkage between two pairs of blood group systems: B-Z and S-F/V respectively.

Five bovine paternal half-sib pedigrees for a total of 527 individuals were typed for six blood group systems: A, B, F/V, L, S, Z; for nine biochemical polymorphisms: ADA, MPI, PGM-3(slow), NP, Gc, Pi2, Tf, Ptf1 and Ptf2; and for restriction fragment length polymorphisms at five autosomal loci: Tg, GH, LDLr, BoLA-DQ and BoLA-DY. Two of the pedigrees were informative for segregation at the 'muscular hypertrophy' locus, and one was informative at the coat colour determining 'roan' locus. Linkage analysis was performed between all markers. Linkage was demonstrated between the S and F/V blood group systems (z = 3.11), adding one locus to the previously identified linkage group VII (LGVII) [Pi-2 and S], the most likely order being Pi2-S-F/V with maximum likelihood recombination rates of 0.208 and 0.211. Also shown to be linked were the blood group systems B and Z (z = 5.7, theta = 0.245). We confirmed the observation previously made by Andersson et al. (1988) of a high recombination rate between class II genes DQ and DY, suggesting either a larger physical distance between those genes than expected from comparative data, or the presence of a 'recombinational hotspot' in the bovine major histocompatibility complex. No linkage was found either with the 'muscular hypertrophy' locus, or with the 'roan' locus. However, these two loci could be excluded from respectively 1.7 and 2.5 Morgans of the bovine genome.

On the use of DNA fingerprints for linkage studies in cattle.

To find a marker for the bovine "muscular hypertrophy" gene and for the "roan" locus, we have typed six cattle pedigrees totaling 540 animals for nine blood group systems, for 12 biochemical markers, for RFLPs at four loci, and with five probes revealing multilocus DNA fingerprints. Segregation analysis of the fingerprint bands showed that, in cattle, a fingerprint probe will reveal a mean of 7.6 clearly resolvable bands, behaving as simple, highly informative Mendelian entities characterized by a mean mutation rate of +/- 1/4500 gametes. For one of the bands, we observed a "mutation burst" generating germline mosaicism. Because some of the fingerprint bands were allelic or corresponded to clustered minisatellites, a mean of only 5.7 independent loci is explored per probe. Fingerprint bands revealed by different probes also show a clear propensity for close linkage, pointing toward nonrandom distribution of minisatellite sequences or the existence of minisatellite clusters. Although this reduces the power of fingerprints for linkage analysis substantially, we were able to demonstrate genetic linkage between fingerprint bands and at least three of the classical markers, to exclude the roan locus from 4.5 Morgans of the bovine genome with the DNA fingerprints and for an additional 2.5 Morgans with the classical markers, and to identify a solid candidate marker for the bovine muscular hypertrophy gene, yielding a lod score greater than or equal to 2.84 without any obliged recombinant.