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.

Antiviral effect of bacterially produced human interferon (Hu-IFN alpha 2) against experimental vaccinia infection in calves.

The heterologous antiviral efficiency of bacterially produced human interferon (Hu-IFN alpha 2) in the bovine species was studied, using vaccinia infection as experimental model. In a double blind experiment, young calves were intramuscularly injected daily for seven consecutive days with different doses of Hu-IFN alpha 2 or placebo, the treatment starting 24 h before intradermal inoculation of vaccinia virus. A clear protection by interferon was observed in all the IFN treated animals, although individual variations in the sensitivity to IFN were recorded. The efficiency of treatment varied according to the dose of IFN used: With the highest dose (10(6) IU/kg), complete protection could be obtained. The only side-effect observed was hyperthermia. Circulating antiviral activity appeared quite early after each IFN injection, presented a more or less biphasic kinetics, and was completely cleared after 24 h, justifying the daily treatment schedule. The first evidence of an in vivo antiviral effect of human interferon in the bovine species opens broad perspectives for a future use of interferon in veterinary medicine.

Experimental rotavirus diarrhoea in colostrum-deprived newborn calves: assay of treatment by administration of bacterially produced human interferon (Hu-IFN alpha 2).

Seven colostrum-deprived newborn calves were orally inoculated within 24 hours after birth with bovine rotavirus. Three of them were intramuscularly injected with bacterially produced human interferon (Hu-IFN alpha 2). The four control animals presented a severe diarrhoea for at least 48 hours, while only one of the treated calves suffered from a transient diarrhoea for a few hours. Hu-IFN alpha 2 seems therefore able to control rotavirus diarrhoea in newborn calves, although it did not inhibit virus excretion and seroconversion in the treated animals. Moreover, the administration of endogenous interferon appeared to be well tolerated by newborn calves. The efficacy of human alpha 2 interferon for the treatment of this important virus infection of cattle seems thus well established.

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.

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.

[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.